fix: Complete snowbridge pezpallet rebrand and critical bug fixes

- snowbridge-pezpallet-* → pezsnowbridge-pezpallet-* (201 refs)
- pallet/ directories → pezpallet/ (4 locations)
- Fixed pezpallet.rs self-include recursion bug
- Fixed sc-chain-spec hardcoded crate name in derive macro
- Reverted .pezpallet_by_name() to .pallet_by_name() (subxt API)
- Added BizinikiwiConfig type alias for zombienet tests
- Deleted obsolete session state files

Verified: pezsnowbridge-pezpallet-*, pezpallet-staking,
pezpallet-staking-async, pezframe-benchmarking-cli all pass cargo check

pezbridges/relays/client-bizinikiwi/src/calls.rs

@@ -0,0 +1,59 @@
+// Copyright 2019-2023 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Basic runtime calls.
+
+use codec::{Decode, Encode};
+use scale_info::TypeInfo;
+use pezsp_std::{boxed::Box, vec::Vec};
+
+use xcm::{VersionedLocation, VersionedXcm};
+
+/// A minimized version of `pezframe-system::Call` that can be used without a runtime.
+#[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
+#[allow(non_camel_case_types)]
+pub enum SystemCall {
+	/// `pezframe-system::Call::remark`
+	#[codec(index = 1)]
+	remark(Vec<u8>),
+}
+
+/// A minimized version of `pezpallet-utility::Call` that can be used without a runtime.
+#[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
+#[allow(non_camel_case_types)]
+pub enum UtilityCall<Call> {
+	/// `pezpallet-utility::Call::batch_all`
+	#[codec(index = 2)]
+	batch_all(Vec<Call>),
+}
+
+/// A minimized version of `pezpallet-sudo::Call` that can be used without a runtime.
+#[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
+#[allow(non_camel_case_types)]
+pub enum SudoCall<Call> {
+	/// `pezpallet-sudo::Call::sudo`
+	#[codec(index = 0)]
+	sudo(Box<Call>),
+}
+
+/// A minimized version of `pezpallet-xcm::Call`, that can be used without a runtime.
+#[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
+#[allow(non_camel_case_types)]
+pub enum XcmCall {
+	/// `pezpallet-xcm::Call::send`
+	#[codec(index = 0)]
+	send(Box<VersionedLocation>, Box<VersionedXcm<()>>),
+}

pezbridges/relays/client-bizinikiwi/src/chain.rs

@@ -0,0 +1,305 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::calls::UtilityCall;
+
+use crate::SimpleRuntimeVersion;
+use bp_header_pez_chain::ChainWithGrandpa as ChainWithGrandpaBase;
+use bp_messages::ChainWithMessages as ChainWithMessagesBase;
+use pezbp_runtime::{
+	Chain as ChainBase, EncodedOrDecodedCall, HashOf, Teyrchain as TeyrchainBase, TransactionEra,
+	TransactionEraOf, UnderlyingChainProvider,
+};
+use codec::{Codec, Decode, Encode, MaxEncodedLen};
+use pezframe_support::Parameter;
+use jsonrpsee::core::{DeserializeOwned, Serialize};
+use num_traits::Zero;
+use pezsc_transaction_pool_api::TransactionStatus;
+use scale_info::TypeInfo;
+use pezsp_core::{storage::StorageKey, Pair};
+use pezsp_runtime::{
+	generic::SignedBlock,
+	traits::{AtLeast32BitUnsigned, Block as BlockT, Member},
+	ConsensusEngineId, EncodedJustification,
+};
+use std::{fmt::Debug, time::Duration};
+
+/// Signed block type of given chain.
+pub type SignedBlockOf<C> = <C as Chain>::SignedBlock;
+
+/// Bizinikiwi-based chain from minimal relay-client point of view.
+pub trait Chain: ChainBase + Clone {
+	/// Chain name.
+	const NAME: &'static str;
+	/// Name of the runtime API method that is returning best known finalized header number
+	/// and hash (as tuple).
+	///
+	/// Keep in mind that this method is normally provided by the other chain, which is
+	/// bridged with this chain.
+	const BEST_FINALIZED_HEADER_ID_METHOD: &'static str;
+	/// Name of the runtime API method that is returning interval between source chain
+	/// headers that may be submitted for free to the target chain.
+	///
+	/// Keep in mind that this method is normally provided by the other chain, which is
+	/// bridged with this chain.
+	const FREE_HEADERS_INTERVAL_METHOD: &'static str;
+
+	/// Average block interval.
+	///
+	/// How often blocks are produced on that chain. It's suggested to set this value
+	/// to match the block time of the chain.
+	const AVERAGE_BLOCK_INTERVAL: Duration;
+
+	/// Block type.
+	type SignedBlock: Member + Serialize + DeserializeOwned + BlockWithJustification<Self::Header>;
+	/// The aggregated `Call` type.
+	type Call: Clone + Codec + Debug + Send + Sync;
+}
+
+/// Bridge-supported network definition.
+///
+/// Used to abstract away CLI commands.
+pub trait ChainWithRuntimeVersion: Chain {
+	/// Current version of the chain runtime, known to relay.
+	///
+	/// can be `None` if relay is not going to submit transactions to that chain.
+	const RUNTIME_VERSION: Option<SimpleRuntimeVersion>;
+}
+
+/// Bizinikiwi-based relay chain that supports teyrchains.
+///
+/// We assume that the teyrchains are supported using `runtime_teyrchains::paras` pezpallet.
+pub trait RelayChain: Chain {
+	/// Name of the `runtime_teyrchains::paras` pezpallet in the runtime of this chain.
+	const PARAS_PALLET_NAME: &'static str;
+	/// Name of the `pezpallet-bridge-teyrchains`, deployed at the **bridged** chain to sync
+	/// teyrchains of **this** chain.
+	const WITH_CHAIN_BRIDGE_TEYRCHAINS_PALLET_NAME: &'static str;
+}
+
+/// Bizinikiwi-based chain that is using direct GRANDPA finality from minimal relay-client point of
+/// view.
+///
+/// Keep in mind that teyrchains are relying on relay chain GRANDPA, so they should not implement
+/// this trait.
+pub trait ChainWithGrandpa: Chain + ChainWithGrandpaBase {
+	/// Name of the runtime API method that is returning the GRANDPA info associated with the
+	/// headers accepted by the `submit_finality_proofs` extrinsic in the queried block.
+	///
+	/// Keep in mind that this method is normally provided by the other chain, which is
+	/// bridged with this chain.
+	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str;
+
+	/// The type of the key owner proof used by the grandpa engine.
+	type KeyOwnerProof: Decode + TypeInfo + Send;
+}
+
+/// Bizinikiwi-based teyrchain from minimal relay-client point of view.
+pub trait Teyrchain: Chain + TeyrchainBase {}
+
+impl<T> Teyrchain for T where T: UnderlyingChainProvider + Chain + TeyrchainBase {}
+
+/// Bizinikiwi-based chain with messaging support from minimal relay-client point of view.
+pub trait ChainWithMessages: Chain + ChainWithMessagesBase {
+	/// Name of the `To<ChainWithMessages>OutboundLaneApi::message_details` runtime API method.
+	/// The method is provided by the runtime that is bridged with this `ChainWithMessages`.
+	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str;
+
+	/// Name of the `From<ChainWithMessages>InboundLaneApi::message_details` runtime API method.
+	/// The method is provided by the runtime that is bridged with this `ChainWithMessages`.
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str;
+}
+
+/// Call type used by the chain.
+pub type CallOf<C> = <C as Chain>::Call;
+/// Transaction status of the chain.
+pub type TransactionStatusOf<C> = TransactionStatus<HashOf<C>, HashOf<C>>;
+
+/// Bizinikiwi-based chain with `AccountData` generic argument of `pezframe_system::AccountInfo` set to
+/// the `pezpallet_balances::AccountData<Balance>`.
+pub trait ChainWithBalances: Chain {
+	/// Return runtime storage key for getting `pezframe_system::AccountInfo` of given account.
+	fn account_info_storage_key(account_id: &Self::AccountId) -> StorageKey;
+}
+
+/// Bizinikiwi-based chain with bridge relayers pezpallet as a reward ledger.
+pub trait ChainWithRewards: Chain {
+	/// Name of the bridge relayers pezpallet (used in `construct_runtime` macro call).
+	const WITH_CHAIN_RELAYERS_PALLET_NAME: Option<&'static str>;
+	/// Type of relayer reward balance.
+	type RewardBalance: AtLeast32BitUnsigned + Copy + Member + Parameter + MaxEncodedLen;
+	/// Reward discriminator type.
+	type Reward: Parameter + MaxEncodedLen + Send + Sync + Copy + Clone;
+
+	/// Return runtime storage key for getting `reward_kind` of given account.
+	fn account_reward_storage_key(
+		account_id: &Self::AccountId,
+		reward: impl Into<Self::Reward>,
+	) -> StorageKey;
+}
+
+/// SCALE-encoded extrinsic.
+pub type EncodedExtrinsic = Vec<u8>;
+
+/// Block with justification.
+pub trait BlockWithJustification<Header> {
+	/// Return block header.
+	fn header(&self) -> Header;
+	/// Return encoded block extrinsics.
+	fn extrinsics(&self) -> Vec<EncodedExtrinsic>;
+	/// Return block justification, if known.
+	fn justification(&self, engine_id: ConsensusEngineId) -> Option<&EncodedJustification>;
+}
+
+/// Transaction before it is signed.
+#[derive(Clone, Debug, PartialEq)]
+pub struct UnsignedTransaction<C: Chain> {
+	/// Runtime call of this transaction.
+	pub call: EncodedOrDecodedCall<C::Call>,
+	/// Transaction nonce.
+	pub nonce: C::Nonce,
+	/// Tip included into transaction.
+	pub tip: C::Balance,
+	/// Transaction era used by the chain.
+	pub era: TransactionEraOf<C>,
+}
+
+impl<C: Chain> UnsignedTransaction<C> {
+	/// Create new unsigned transaction with given call, nonce, era and zero tip.
+	pub fn new(call: EncodedOrDecodedCall<C::Call>, nonce: C::Nonce) -> Self {
+		Self { call, nonce, era: TransactionEra::Immortal, tip: Zero::zero() }
+	}
+
+	/// Convert to the transaction of the other compatible chain.
+	pub fn switch_chain<Other>(self) -> UnsignedTransaction<Other>
+	where
+		Other: Chain<
+			Nonce = C::Nonce,
+			Balance = C::Balance,
+			BlockNumber = C::BlockNumber,
+			Hash = C::Hash,
+		>,
+	{
+		UnsignedTransaction {
+			call: EncodedOrDecodedCall::Encoded(self.call.into_encoded()),
+			nonce: self.nonce,
+			tip: self.tip,
+			era: self.era,
+		}
+	}
+
+	/// Set transaction tip.
+	#[must_use]
+	pub fn tip(mut self, tip: C::Balance) -> Self {
+		self.tip = tip;
+		self
+	}
+
+	/// Set transaction era.
+	#[must_use]
+	pub fn era(mut self, era: TransactionEraOf<C>) -> Self {
+		self.era = era;
+		self
+	}
+}
+
+/// Account key pair used by transactions signing scheme.
+pub type AccountKeyPairOf<S> = <S as ChainWithTransactions>::AccountKeyPair;
+
+/// Bizinikiwi-based chain transactions signing scheme.
+pub trait ChainWithTransactions: Chain {
+	/// Type of key pairs used to sign transactions.
+	type AccountKeyPair: Pair + Clone + Send + Sync;
+	/// Signed transaction.
+	type SignedTransaction: Clone + Debug + Encode + Send + 'static;
+
+	/// Create transaction for given runtime call, signed by given account.
+	fn sign_transaction(
+		param: SignParam<Self>,
+		unsigned: UnsignedTransaction<Self>,
+	) -> Result<Self::SignedTransaction, crate::Error>
+	where
+		Self: Sized;
+}
+
+/// Sign transaction parameters
+pub struct SignParam<C: ChainWithTransactions> {
+	/// Version of the runtime specification.
+	pub spec_version: u32,
+	/// Transaction version
+	pub transaction_version: u32,
+	/// Hash of the genesis block.
+	pub genesis_hash: HashOf<C>,
+	/// Signer account
+	pub signer: AccountKeyPairOf<C>,
+}
+
+impl<Block: BlockT> BlockWithJustification<Block::Header> for SignedBlock<Block> {
+	fn header(&self) -> Block::Header {
+		self.block.header().clone()
+	}
+
+	fn extrinsics(&self) -> Vec<EncodedExtrinsic> {
+		self.block.extrinsics().iter().map(Encode::encode).collect()
+	}
+
+	fn justification(&self, engine_id: ConsensusEngineId) -> Option<&EncodedJustification> {
+		self.justifications.as_ref().and_then(|j| j.get(engine_id))
+	}
+}
+
+/// Trait that provides functionality defined inside `pezpallet-utility`
+pub trait UtilityPallet<C: Chain> {
+	/// Create batch call from given calls vector.
+	fn build_batch_call(calls: Vec<C::Call>) -> C::Call;
+}
+
+/// Structure that implements `UtilityPalletProvider` based on a full runtime.
+pub struct FullRuntimeUtilityPallet<R> {
+	_phantom: std::marker::PhantomData<R>,
+}
+
+impl<C, R> UtilityPallet<C> for FullRuntimeUtilityPallet<R>
+where
+	C: Chain,
+	R: pezpallet_utility::Config<RuntimeCall = C::Call>,
+	<R as pezpallet_utility::Config>::RuntimeCall: From<pezpallet_utility::Call<R>>,
+{
+	fn build_batch_call(calls: Vec<C::Call>) -> C::Call {
+		pezpallet_utility::Call::batch_all { calls }.into()
+	}
+}
+
+/// Structure that implements `UtilityPalletProvider` based on a call conversion.
+pub struct MockedRuntimeUtilityPallet<Call> {
+	_phantom: std::marker::PhantomData<Call>,
+}
+
+impl<C, Call> UtilityPallet<C> for MockedRuntimeUtilityPallet<Call>
+where
+	C: Chain,
+	C::Call: From<UtilityCall<C::Call>>,
+{
+	fn build_batch_call(calls: Vec<C::Call>) -> C::Call {
+		UtilityCall::batch_all(calls).into()
+	}
+}
+
+/// Bizinikiwi-based chain that uses `pezpallet-utility`.
+pub trait ChainWithUtilityPallet: Chain {
+	/// The utility pezpallet provider.
+	type UtilityPallet: UtilityPallet<Self>;
+}

pezbridges/relays/client-bizinikiwi/src/client/caching.rs

@@ -0,0 +1,472 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Client implementation that is caching (whenever possible) results of its backend
+//! method calls.
+
+use crate::{
+	client::{Client, SubscriptionBroadcaster},
+	error::{Error, Result},
+	AccountIdOf, AccountKeyPairOf, BlockNumberOf, Chain, ChainWithGrandpa, ChainWithTransactions,
+	HashOf, HeaderIdOf, HeaderOf, NonceOf, SignedBlockOf, SimpleRuntimeVersion, Subscription,
+	TransactionTracker, UnsignedTransaction, ANCIENT_BLOCK_THRESHOLD,
+};
+use std::{cmp::Ordering, future::Future, task::Poll};
+
+use async_std::{
+	sync::{Arc, Mutex, RwLock},
+	task::JoinHandle,
+};
+use async_trait::async_trait;
+use codec::Encode;
+use pezframe_support::weights::Weight;
+use futures::{FutureExt, StreamExt};
+use quick_cache::unsync::Cache;
+use pezsp_consensus_grandpa::{AuthorityId, OpaqueKeyOwnershipProof, SetId};
+use pezsp_core::{
+	storage::{StorageData, StorageKey},
+	Bytes, Pair,
+};
+use pezsp_runtime::{traits::Header as _, transaction_validity::TransactionValidity};
+use pezsp_trie::StorageProof;
+use pezsp_version::RuntimeVersion;
+
+/// `quick_cache::unsync::Cache` wrapped in async-aware synchronization primitives.
+type SyncCache<K, V> = Arc<RwLock<Cache<K, V>>>;
+
+/// Client implementation that is caching (whenever possible) results of its backend
+/// method calls. Apart from caching call results, it also supports some (at the
+/// moment: justifications) subscription sharing, meaning that the single server
+/// subscription may be shared by multiple subscribers at the client side.
+#[derive(Clone)]
+pub struct CachingClient<C: Chain, B: Client<C>> {
+	backend: B,
+	data: Arc<ClientData<C>>,
+}
+
+/// Client data, shared by all `CachingClient` clones.
+struct ClientData<C: Chain> {
+	grandpa_justifications: Arc<Mutex<Option<SubscriptionBroadcaster<Bytes>>>>,
+	beefy_justifications: Arc<Mutex<Option<SubscriptionBroadcaster<Bytes>>>>,
+	background_task_handle: Arc<Mutex<JoinHandle<Result<()>>>>,
+	best_header: Arc<RwLock<Option<HeaderOf<C>>>>,
+	best_finalized_header: Arc<RwLock<Option<HeaderOf<C>>>>,
+	// `quick_cache::sync::Cache` has the `get_or_insert_async` method, which fits our needs,
+	// but it uses synchronization primitives that are not aware of async execution. They
+	// can block the executor threads and cause deadlocks => let's use primitives from
+	// `async_std` crate around `quick_cache::unsync::Cache`
+	header_hash_by_number_cache: SyncCache<BlockNumberOf<C>, HashOf<C>>,
+	header_by_hash_cache: SyncCache<HashOf<C>, HeaderOf<C>>,
+	block_by_hash_cache: SyncCache<HashOf<C>, SignedBlockOf<C>>,
+	raw_storage_value_cache: SyncCache<(HashOf<C>, StorageKey), Option<StorageData>>,
+	state_call_cache: SyncCache<(HashOf<C>, String, Bytes), Bytes>,
+}
+
+impl<C: Chain, B: Client<C>> CachingClient<C, B> {
+	/// Creates new `CachingClient` on top of given `backend`.
+	pub async fn new(backend: B) -> Self {
+		// most of relayer operations will never touch more than `ANCIENT_BLOCK_THRESHOLD`
+		// headers, so we'll use this as a cache capacity for all chain-related caches
+		let chain_state_capacity = ANCIENT_BLOCK_THRESHOLD as usize;
+		let best_header = Arc::new(RwLock::new(None));
+		let best_finalized_header = Arc::new(RwLock::new(None));
+		let header_by_hash_cache = Arc::new(RwLock::new(Cache::new(chain_state_capacity)));
+		let background_task_handle = Self::start_background_task(
+			backend.clone(),
+			best_header.clone(),
+			best_finalized_header.clone(),
+			header_by_hash_cache.clone(),
+		)
+		.await;
+		CachingClient {
+			backend,
+			data: Arc::new(ClientData {
+				grandpa_justifications: Arc::new(Mutex::new(None)),
+				beefy_justifications: Arc::new(Mutex::new(None)),
+				background_task_handle: Arc::new(Mutex::new(background_task_handle)),
+				best_header,
+				best_finalized_header,
+				header_hash_by_number_cache: Arc::new(RwLock::new(Cache::new(
+					chain_state_capacity,
+				))),
+				header_by_hash_cache,
+				block_by_hash_cache: Arc::new(RwLock::new(Cache::new(chain_state_capacity))),
+				raw_storage_value_cache: Arc::new(RwLock::new(Cache::new(1_024))),
+				state_call_cache: Arc::new(RwLock::new(Cache::new(1_024))),
+			}),
+		}
+	}
+
+	/// Try to get value from the cache, or compute and insert it using given future.
+	async fn get_or_insert_async<K: Clone + std::fmt::Debug + Eq + std::hash::Hash, V: Clone>(
+		&self,
+		cache: &Arc<RwLock<Cache<K, V>>>,
+		key: &K,
+		with: impl std::future::Future<Output = Result<V>>,
+	) -> Result<V> {
+		// try to get cached value first using read lock
+		{
+			let cache = cache.read().await;
+			if let Some(value) = cache.get(key) {
+				return Ok(value.clone());
+			}
+		}
+
+		// let's compute the value without holding any locks - it may cause additional misses and
+		// double insertions, but that's better than holding a lock for a while
+		let value = with.await?;
+
+		// insert/update the value in the cache
+		cache.write().await.insert(key.clone(), value.clone());
+		Ok(value)
+	}
+
+	/// Subscribe to finality justifications, trying to reuse existing subscription.
+	async fn subscribe_finality_justifications<'a>(
+		&'a self,
+		maybe_broadcaster: &Mutex<Option<SubscriptionBroadcaster<Bytes>>>,
+		do_subscribe: impl Future<Output = Result<Subscription<Bytes>>> + 'a,
+	) -> Result<Subscription<Bytes>> {
+		let mut maybe_broadcaster = maybe_broadcaster.lock().await;
+		let broadcaster = match maybe_broadcaster.as_ref() {
+			Some(justifications) => justifications,
+			None => {
+				let broadcaster = match SubscriptionBroadcaster::new(do_subscribe.await?) {
+					Ok(broadcaster) => broadcaster,
+					Err(subscription) => return Ok(subscription),
+				};
+				maybe_broadcaster.get_or_insert(broadcaster)
+			},
+		};
+
+		broadcaster.subscribe().await
+	}
+
+	/// Start background task that reads best (and best finalized) headers from subscriptions.
+	async fn start_background_task(
+		backend: B,
+		best_header: Arc<RwLock<Option<HeaderOf<C>>>>,
+		best_finalized_header: Arc<RwLock<Option<HeaderOf<C>>>>,
+		header_by_hash_cache: SyncCache<HashOf<C>, HeaderOf<C>>,
+	) -> JoinHandle<Result<()>> {
+		async_std::task::spawn(async move {
+			// initialize by reading headers directly from backend to avoid doing that in the
+			// high-level code
+			let mut last_finalized_header =
+				backend.header_by_hash(backend.best_finalized_header_hash().await?).await?;
+			*best_header.write().await = Some(backend.best_header().await?);
+			*best_finalized_header.write().await = Some(last_finalized_header.clone());
+
+			// ...and then continue with subscriptions
+			let mut best_headers = backend.subscribe_best_headers().await?;
+			let mut finalized_headers = backend.subscribe_finalized_headers().await?;
+			loop {
+				futures::select! {
+					new_best_header = best_headers.next().fuse() => {
+						// we assume that the best header is always the actual best header, even if its
+						// number is lower than the number of previous-best-header (chain may use its own
+						// best header selection algorithms)
+						let new_best_header = new_best_header
+							.ok_or_else(|| Error::ChannelError(format!("Mandatory best headers subscription for {} has finished", C::NAME)))?;
+						let new_best_header_hash = new_best_header.hash();
+						header_by_hash_cache.write().await.insert(new_best_header_hash, new_best_header.clone());
+						*best_header.write().await = Some(new_best_header);
+					},
+					new_finalized_header = finalized_headers.next().fuse() => {
+						// in theory we'll always get finalized headers in order, but let's double check
+						let new_finalized_header = new_finalized_header.
+							ok_or_else(|| Error::ChannelError(format!("Finalized headers subscription for {} has finished", C::NAME)))?;
+						let new_finalized_header_number = *new_finalized_header.number();
+						let last_finalized_header_number = *last_finalized_header.number();
+						match new_finalized_header_number.cmp(&last_finalized_header_number) {
+							Ordering::Greater => {
+								let new_finalized_header_hash = new_finalized_header.hash();
+								header_by_hash_cache.write().await.insert(new_finalized_header_hash, new_finalized_header.clone());
+								*best_finalized_header.write().await = Some(new_finalized_header.clone());
+								last_finalized_header = new_finalized_header;
+							},
+							Ordering::Less => {
+								return Err(Error::unordered_finalized_headers::<C>(
+									new_finalized_header_number,
+									last_finalized_header_number,
+								));
+							},
+							_ => (),
+						}
+					},
+				}
+			}
+		})
+	}
+
+	/// Ensure that the background task is active.
+	async fn ensure_background_task_active(&self) -> Result<()> {
+		let mut background_task_handle = self.data.background_task_handle.lock().await;
+		if let Poll::Ready(result) = futures::poll!(&mut *background_task_handle) {
+			return Err(Error::ChannelError(format!(
+				"Background task of {} client has exited with result: {:?}",
+				C::NAME,
+				result
+			)));
+		}
+
+		Ok(())
+	}
+
+	/// Try to get header, read elsewhere by background task through subscription.
+	async fn read_header_from_background<'a>(
+		&'a self,
+		header: &Arc<RwLock<Option<HeaderOf<C>>>>,
+		read_header_from_backend: impl Future<Output = Result<HeaderOf<C>>> + 'a,
+	) -> Result<HeaderOf<C>> {
+		// ensure that the background task is active
+		self.ensure_background_task_active().await?;
+
+		// now we know that the background task is active, so we could trust that the
+		// `header` has the most recent updates from it
+		match header.read().await.clone() {
+			Some(header) => Ok(header),
+			None => {
+				// header has not yet been read from the subscription, which means that
+				// we are just starting - let's read header directly from backend this time
+				read_header_from_backend.await
+			},
+		}
+	}
+}
+
+impl<C: Chain, B: Client<C>> std::fmt::Debug for CachingClient<C, B> {
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		fmt.write_fmt(format_args!("CachingClient<{:?}>", self.backend))
+	}
+}
+
+#[async_trait]
+impl<C: Chain, B: Client<C>> Client<C> for CachingClient<C, B> {
+	async fn ensure_synced(&self) -> Result<()> {
+		self.backend.ensure_synced().await
+	}
+
+	async fn reconnect(&self) -> Result<()> {
+		self.backend.reconnect().await?;
+		// since we have new underlying client, we need to restart subscriptions too
+		*self.data.grandpa_justifications.lock().await = None;
+		*self.data.beefy_justifications.lock().await = None;
+		// also restart background task too
+		*self.data.best_header.write().await = None;
+		*self.data.best_finalized_header.write().await = None;
+		*self.data.background_task_handle.lock().await = Self::start_background_task(
+			self.backend.clone(),
+			self.data.best_header.clone(),
+			self.data.best_finalized_header.clone(),
+			self.data.header_by_hash_cache.clone(),
+		)
+		.await;
+		Ok(())
+	}
+
+	fn genesis_hash(&self) -> HashOf<C> {
+		self.backend.genesis_hash()
+	}
+
+	async fn header_hash_by_number(&self, number: BlockNumberOf<C>) -> Result<HashOf<C>> {
+		self.get_or_insert_async(
+			&self.data.header_hash_by_number_cache,
+			&number,
+			self.backend.header_hash_by_number(number),
+		)
+		.await
+	}
+
+	async fn header_by_hash(&self, hash: HashOf<C>) -> Result<HeaderOf<C>> {
+		self.get_or_insert_async(
+			&self.data.header_by_hash_cache,
+			&hash,
+			self.backend.header_by_hash(hash),
+		)
+		.await
+	}
+
+	async fn block_by_hash(&self, hash: HashOf<C>) -> Result<SignedBlockOf<C>> {
+		self.get_or_insert_async(
+			&self.data.block_by_hash_cache,
+			&hash,
+			self.backend.block_by_hash(hash),
+		)
+		.await
+	}
+
+	async fn best_finalized_header_hash(&self) -> Result<HashOf<C>> {
+		self.read_header_from_background(
+			&self.data.best_finalized_header,
+			self.backend.best_finalized_header(),
+		)
+		.await
+		.map(|h| h.hash())
+	}
+
+	async fn best_header(&self) -> Result<HeaderOf<C>> {
+		self.read_header_from_background(&self.data.best_header, self.backend.best_header())
+			.await
+	}
+
+	async fn subscribe_best_headers(&self) -> Result<Subscription<HeaderOf<C>>> {
+		// we may share the sunbscription here, but atm there's no callers of this method
+		self.backend.subscribe_best_headers().await
+	}
+
+	async fn subscribe_finalized_headers(&self) -> Result<Subscription<HeaderOf<C>>> {
+		// we may share the sunbscription here, but atm there's no callers of this method
+		self.backend.subscribe_finalized_headers().await
+	}
+
+	async fn subscribe_grandpa_finality_justifications(&self) -> Result<Subscription<Bytes>>
+	where
+		C: ChainWithGrandpa,
+	{
+		self.subscribe_finality_justifications(
+			&self.data.grandpa_justifications,
+			self.backend.subscribe_grandpa_finality_justifications(),
+		)
+		.await
+	}
+
+	async fn generate_grandpa_key_ownership_proof(
+		&self,
+		at: HashOf<C>,
+		set_id: SetId,
+		authority_id: AuthorityId,
+	) -> Result<Option<OpaqueKeyOwnershipProof>> {
+		self.backend
+			.generate_grandpa_key_ownership_proof(at, set_id, authority_id)
+			.await
+	}
+
+	async fn subscribe_beefy_finality_justifications(&self) -> Result<Subscription<Bytes>> {
+		self.subscribe_finality_justifications(
+			&self.data.beefy_justifications,
+			self.backend.subscribe_beefy_finality_justifications(),
+		)
+		.await
+	}
+
+	async fn token_decimals(&self) -> Result<Option<u64>> {
+		self.backend.token_decimals().await
+	}
+
+	async fn runtime_version(&self) -> Result<RuntimeVersion> {
+		self.backend.runtime_version().await
+	}
+
+	async fn simple_runtime_version(&self) -> Result<SimpleRuntimeVersion> {
+		self.backend.simple_runtime_version().await
+	}
+
+	fn can_start_version_guard(&self) -> bool {
+		self.backend.can_start_version_guard()
+	}
+
+	async fn raw_storage_value(
+		&self,
+		at: HashOf<C>,
+		storage_key: StorageKey,
+	) -> Result<Option<StorageData>> {
+		self.get_or_insert_async(
+			&self.data.raw_storage_value_cache,
+			&(at, storage_key.clone()),
+			self.backend.raw_storage_value(at, storage_key),
+		)
+		.await
+	}
+
+	async fn pending_extrinsics(&self) -> Result<Vec<Bytes>> {
+		self.backend.pending_extrinsics().await
+	}
+
+	async fn submit_unsigned_extrinsic(&self, transaction: Bytes) -> Result<HashOf<C>> {
+		self.backend.submit_unsigned_extrinsic(transaction).await
+	}
+
+	async fn submit_signed_extrinsic(
+		&self,
+		signer: &AccountKeyPairOf<C>,
+		prepare_extrinsic: impl FnOnce(HeaderIdOf<C>, NonceOf<C>) -> Result<UnsignedTransaction<C>>
+			+ Send
+			+ 'static,
+	) -> Result<HashOf<C>>
+	where
+		C: ChainWithTransactions,
+		AccountIdOf<C>: From<<AccountKeyPairOf<C> as Pair>::Public>,
+	{
+		self.backend.submit_signed_extrinsic(signer, prepare_extrinsic).await
+	}
+
+	async fn submit_and_watch_signed_extrinsic(
+		&self,
+		signer: &AccountKeyPairOf<C>,
+		prepare_extrinsic: impl FnOnce(HeaderIdOf<C>, NonceOf<C>) -> Result<UnsignedTransaction<C>>
+			+ Send
+			+ 'static,
+	) -> Result<TransactionTracker<C, Self>>
+	where
+		C: ChainWithTransactions,
+		AccountIdOf<C>: From<<AccountKeyPairOf<C> as Pair>::Public>,
+	{
+		self.backend
+			.submit_and_watch_signed_extrinsic(signer, prepare_extrinsic)
+			.await
+			.map(|t| t.switch_environment(self.clone()))
+	}
+
+	async fn validate_transaction<SignedTransaction: Encode + Send + 'static>(
+		&self,
+		at: HashOf<C>,
+		transaction: SignedTransaction,
+	) -> Result<TransactionValidity> {
+		self.backend.validate_transaction(at, transaction).await
+	}
+
+	async fn estimate_extrinsic_weight<SignedTransaction: Encode + Send + 'static>(
+		&self,
+		at: HashOf<C>,
+		transaction: SignedTransaction,
+	) -> Result<Weight> {
+		self.backend.estimate_extrinsic_weight(at, transaction).await
+	}
+
+	async fn raw_state_call<Args: Encode + Send>(
+		&self,
+		at: HashOf<C>,
+		method: String,
+		arguments: Args,
+	) -> Result<Bytes> {
+		let encoded_arguments = Bytes(arguments.encode());
+		self.get_or_insert_async(
+			&self.data.state_call_cache,
+			&(at, method.clone(), encoded_arguments),
+			self.backend.raw_state_call(at, method, arguments),
+		)
+		.await
+	}
+
+	async fn prove_storage(
+		&self,
+		at: HashOf<C>,
+		keys: Vec<StorageKey>,
+	) -> Result<(StorageProof, HashOf<C>)> {
+		self.backend.prove_storage(at, keys).await
+	}
+}

pezbridges/relays/client-bizinikiwi/src/client/mod.rs

@@ -0,0 +1,91 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Layered Bizinikiwi client implementation.
+
+use crate::{Chain, ConnectionParams};
+
+use caching::CachingClient;
+use num_traits::Saturating;
+use rpc::RpcClient;
+use pezsp_version::RuntimeVersion;
+
+pub mod caching;
+pub mod rpc;
+
+mod rpc_api;
+mod subscription;
+mod traits;
+
+pub use subscription::{StreamDescription, Subscription, SubscriptionBroadcaster};
+pub use traits::Client;
+
+/// Type of RPC client with caching support.
+pub type RpcWithCachingClient<C> = CachingClient<C, RpcClient<C>>;
+
+/// Creates new RPC client with caching support.
+pub async fn rpc_with_caching<C: Chain>(params: ConnectionParams) -> RpcWithCachingClient<C> {
+	let rpc = rpc::RpcClient::<C>::new(params).await;
+	caching::CachingClient::new(rpc).await
+}
+
+/// The difference between best block number and number of its ancestor, that is enough
+/// for us to consider that ancestor an "ancient" block with dropped state.
+///
+/// The relay does not assume that it is connected to the archive node, so it always tries
+/// to use the best available chain state. But sometimes it still may use state of some
+/// old block. If the state of that block is already dropped, relay will see errors when
+/// e.g. it tries to prove something.
+///
+/// By default Bizinikiwi-based nodes are storing state for last 256 blocks. We'll use
+/// half of this value.
+pub const ANCIENT_BLOCK_THRESHOLD: u32 = 128;
+
+/// Returns `true` if we think that the state is already discarded for given block.
+pub fn is_ancient_block<N: From<u32> + PartialOrd + Saturating>(block: N, best: N) -> bool {
+	best.saturating_sub(block) >= N::from(ANCIENT_BLOCK_THRESHOLD)
+}
+
+/// Opaque GRANDPA authorities set.
+pub type OpaqueGrandpaAuthoritiesSet = Vec<u8>;
+
+/// A simple runtime version. It only includes the `spec_version` and `transaction_version`.
+#[derive(Copy, Clone, Debug)]
+pub struct SimpleRuntimeVersion {
+	/// Version of the runtime specification.
+	pub spec_version: u32,
+	/// All existing dispatches are fully compatible when this number doesn't change.
+	pub transaction_version: u32,
+}
+
+impl SimpleRuntimeVersion {
+	/// Create a new instance of `SimpleRuntimeVersion` from a `RuntimeVersion`.
+	pub const fn from_runtime_version(runtime_version: &RuntimeVersion) -> Self {
+		Self {
+			spec_version: runtime_version.spec_version,
+			transaction_version: runtime_version.transaction_version,
+		}
+	}
+}
+
+/// Chain runtime version in client
+#[derive(Copy, Clone, Debug)]
+pub enum ChainRuntimeVersion {
+	/// Auto query from chain.
+	Auto,
+	/// Custom runtime version, defined by user.
+	Custom(SimpleRuntimeVersion),
+}

pezbridges/relays/client-bizinikiwi/src/client/rpc.rs

@@ -0,0 +1,743 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Client implementation that connects to the Bizinikiwi node over `ws`/`wss` connection
+//! and is using RPC methods to get required data and submit transactions.
+
+use crate::{
+	client::{
+		rpc_api::{
+			BizinikiwiAuthorClient, BizinikiwiBeefyClient, BizinikiwiChainClient,
+			BizinikiwiFrameSystemClient, BizinikiwiGrandpaClient, BizinikiwiStateClient,
+			BizinikiwiSystemClient,
+		},
+		subscription::{StreamDescription, Subscription},
+		Client,
+	},
+	error::{Error, Result},
+	guard::Environment,
+	transaction_stall_timeout, AccountIdOf, AccountKeyPairOf, BalanceOf, BlockNumberOf, Chain,
+	ChainRuntimeVersion, ChainWithGrandpa, ChainWithTransactions, ConnectionParams, HashOf,
+	HeaderIdOf, HeaderOf, NonceOf, SignParam, SignedBlockOf, SimpleRuntimeVersion,
+	TransactionTracker, UnsignedTransaction,
+};
+
+use async_std::sync::{Arc, Mutex, RwLock};
+use async_trait::async_trait;
+use pezbp_runtime::HeaderIdProvider;
+use codec::Encode;
+use pezframe_support::weights::Weight;
+use futures::TryFutureExt;
+use jsonrpsee::{
+	core::{client::Subscription as RpcSubscription, ClientError},
+	ws_client::{WsClient, WsClientBuilder},
+};
+use num_traits::Zero;
+use pezpallet_transaction_payment::RuntimeDispatchInfo;
+use relay_utils::{relay_loop::RECONNECT_DELAY, STALL_TIMEOUT};
+use pezsp_core::{
+	storage::{StorageData, StorageKey},
+	Bytes, Hasher, Pair,
+};
+use pezsp_runtime::{
+	traits::Header,
+	transaction_validity::{TransactionSource, TransactionValidity},
+};
+use pezsp_trie::StorageProof;
+use pezsp_version::RuntimeVersion;
+use std::{cmp::Ordering, future::Future, marker::PhantomData};
+
+const MAX_SUBSCRIPTION_CAPACITY: usize = 4096;
+
+const SUB_API_TXPOOL_VALIDATE_TRANSACTION: &str = "TaggedTransactionQueue_validate_transaction";
+const SUB_API_TX_PAYMENT_QUERY_INFO: &str = "TransactionPaymentApi_query_info";
+const SUB_API_GRANDPA_GENERATE_KEY_OWNERSHIP_PROOF: &str =
+	"GrandpaApi_generate_key_ownership_proof";
+
+/// Client implementation that connects to the Bizinikiwi node over `ws`/`wss` connection
+/// and is using RPC methods to get required data and submit transactions.
+pub struct RpcClient<C: Chain> {
+	// Lock order: `submit_signed_extrinsic_lock`, `data`
+	/// Client connection params.
+	params: Arc<ConnectionParams>,
+	/// If several tasks are submitting their transactions simultaneously using
+	/// `submit_signed_extrinsic` method, they may get the same transaction nonce. So one of
+	/// transactions will be rejected from the pool. This lock is here to prevent situations like
+	/// that.
+	submit_signed_extrinsic_lock: Arc<Mutex<()>>,
+	/// Genesis block hash.
+	genesis_hash: HashOf<C>,
+	/// Shared dynamic data.
+	data: Arc<RwLock<ClientData>>,
+	/// Generic arguments dump.
+	_phantom: PhantomData<C>,
+}
+
+/// Client data, shared by all `RpcClient` clones.
+struct ClientData {
+	/// Tokio runtime handle.
+	tokio: Arc<tokio::runtime::Runtime>,
+	/// Bizinikiwi RPC client.
+	client: Arc<WsClient>,
+}
+
+/// Already encoded value.
+struct PreEncoded(Vec<u8>);
+
+impl Encode for PreEncoded {
+	fn encode(&self) -> Vec<u8> {
+		self.0.clone()
+	}
+}
+
+impl<C: Chain> std::fmt::Debug for RpcClient<C> {
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		fmt.write_fmt(format_args!("RpcClient<{}>", C::NAME))
+	}
+}
+
+impl<C: Chain> RpcClient<C> {
+	/// Returns client that is able to call RPCs on Bizinikiwi node over websocket connection.
+	///
+	/// This function will keep connecting to given Bizinikiwi node until connection is established
+	/// and is functional. If attempt fail, it will wait for `RECONNECT_DELAY` and retry again.
+	pub async fn new(params: ConnectionParams) -> Self {
+		let params = Arc::new(params);
+		loop {
+			match Self::try_connect(params.clone()).await {
+				Ok(client) => return client,
+				Err(error) => tracing::error!(
+					target: "bridge",
+					?error,
+					node=%C::NAME,
+					retry_as_secs=%RECONNECT_DELAY.as_secs(),
+					"Failed to connect. Going to retry"
+				),
+			}
+
+			async_std::task::sleep(RECONNECT_DELAY).await;
+		}
+	}
+
+	/// Try to connect to Bizinikiwi node over websocket. Returns Bizinikiwi RPC client if connection
+	/// has been established or error otherwise.
+	async fn try_connect(params: Arc<ConnectionParams>) -> Result<Self> {
+		let (tokio, client) = Self::build_client(&params).await?;
+
+		let genesis_hash_client = client.clone();
+		let genesis_hash = tokio
+			.spawn(async move {
+				BizinikiwiChainClient::<C>::block_hash(&*genesis_hash_client, Some(Zero::zero()))
+					.await
+			})
+			.await??;
+
+		let chain_runtime_version = params.chain_runtime_version;
+		let mut client = Self {
+			params,
+			submit_signed_extrinsic_lock: Arc::new(Mutex::new(())),
+			genesis_hash,
+			data: Arc::new(RwLock::new(ClientData { tokio, client })),
+			_phantom: PhantomData,
+		};
+		Self::ensure_correct_runtime_version(&mut client, chain_runtime_version).await?;
+		Ok(client)
+	}
+
+	// Check runtime version to understand if we need are connected to expected version, or we
+	// need to wait for upgrade, we need to abort immediately.
+	async fn ensure_correct_runtime_version<E: Environment<C, Error = Error>>(
+		env: &mut E,
+		expected: ChainRuntimeVersion,
+	) -> Result<()> {
+		// we are only interested if version mode is bundled or passed using CLI
+		let expected = match expected {
+			ChainRuntimeVersion::Auto => return Ok(()),
+			ChainRuntimeVersion::Custom(expected) => expected,
+		};
+
+		// we need to wait if actual version is < than expected, we are OK of versions are the
+		// same and we need to abort if actual version is > than expected
+		let actual = SimpleRuntimeVersion::from_runtime_version(&env.runtime_version().await?);
+		match actual.spec_version.cmp(&expected.spec_version) {
+			Ordering::Less =>
+				Err(Error::WaitingForRuntimeUpgrade { chain: C::NAME.into(), expected, actual }),
+			Ordering::Equal => Ok(()),
+			Ordering::Greater => {
+				tracing::error!(
+					target: "bridge",
+					node=%C::NAME,
+					?expected,
+					?actual,
+					"The client is configured to use runtime version, which is different from the \
+					actual version. Aborting",
+				);
+				env.abort().await;
+				Err(Error::Custom("Aborted".into()))
+			},
+		}
+	}
+
+	/// Build client to use in connection.
+	async fn build_client(
+		params: &ConnectionParams,
+	) -> Result<(Arc<tokio::runtime::Runtime>, Arc<WsClient>)> {
+		let tokio = tokio::runtime::Runtime::new()?;
+		let uri = params.uri.clone();
+		tracing::info!(target: "bridge", node=%C::NAME, %uri, "Connecting");
+
+		let client = tokio
+			.spawn(async move {
+				WsClientBuilder::default()
+					.max_buffer_capacity_per_subscription(MAX_SUBSCRIPTION_CAPACITY)
+					.build(&uri)
+					.await
+			})
+			.await??;
+
+		Ok((Arc::new(tokio), Arc::new(client)))
+	}
+
+	/// Execute jsonrpsee future in tokio context.
+	async fn jsonrpsee_execute<MF, F, T>(&self, make_jsonrpsee_future: MF) -> Result<T>
+	where
+		MF: FnOnce(Arc<WsClient>) -> F + Send + 'static,
+		F: Future<Output = Result<T>> + Send + 'static,
+		T: Send + 'static,
+	{
+		let data = self.data.read().await;
+		let client = data.client.clone();
+		data.tokio.spawn(make_jsonrpsee_future(client)).await?
+	}
+
+	/// Prepare parameters used to sign chain transactions.
+	async fn build_sign_params(&self, signer: AccountKeyPairOf<C>) -> Result<SignParam<C>>
+	where
+		C: ChainWithTransactions,
+	{
+		let runtime_version = self.simple_runtime_version().await?;
+		Ok(SignParam::<C> {
+			spec_version: runtime_version.spec_version,
+			transaction_version: runtime_version.transaction_version,
+			genesis_hash: self.genesis_hash,
+			signer,
+		})
+	}
+
+	/// Get the nonce of the given Bizinikiwi account.
+	pub async fn next_account_index(&self, account: AccountIdOf<C>) -> Result<NonceOf<C>> {
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiFrameSystemClient::<C>::account_next_index(&*client, account).await?)
+		})
+		.await
+	}
+
+	/// Subscribe to finality justifications.
+	async fn subscribe_finality_justifications<Fut>(
+		&self,
+		gadget_name: &str,
+		do_subscribe: impl FnOnce(Arc<WsClient>) -> Fut + Send + 'static,
+	) -> Result<Subscription<Bytes>>
+	where
+		Fut: Future<Output = std::result::Result<RpcSubscription<Bytes>, ClientError>> + Send,
+	{
+		let subscription = self
+			.jsonrpsee_execute(move |client| async move { Ok(do_subscribe(client).await?) })
+			.map_err(|e| Error::failed_to_subscribe_justification::<C>(e))
+			.await?;
+
+		Ok(Subscription::new_forwarded(
+			StreamDescription::new(format!("{} justifications", gadget_name), C::NAME.into()),
+			subscription,
+		))
+	}
+
+	/// Subscribe to headers stream.
+	async fn subscribe_headers<Fut>(
+		&self,
+		stream_name: &str,
+		do_subscribe: impl FnOnce(Arc<WsClient>) -> Fut + Send + 'static,
+		map_err: impl FnOnce(Error) -> Error,
+	) -> Result<Subscription<HeaderOf<C>>>
+	where
+		Fut: Future<Output = std::result::Result<RpcSubscription<HeaderOf<C>>, ClientError>> + Send,
+	{
+		let subscription = self
+			.jsonrpsee_execute(move |client| async move { Ok(do_subscribe(client).await?) })
+			.map_err(map_err)
+			.await?;
+
+		Ok(Subscription::new_forwarded(
+			StreamDescription::new(format!("{} headers", stream_name), C::NAME.into()),
+			subscription,
+		))
+	}
+}
+
+impl<C: Chain> Clone for RpcClient<C> {
+	fn clone(&self) -> Self {
+		RpcClient {
+			params: self.params.clone(),
+			submit_signed_extrinsic_lock: self.submit_signed_extrinsic_lock.clone(),
+			genesis_hash: self.genesis_hash,
+			data: self.data.clone(),
+			_phantom: PhantomData,
+		}
+	}
+}
+
+#[async_trait]
+impl<C: Chain> Client<C> for RpcClient<C> {
+	async fn ensure_synced(&self) -> Result<()> {
+		let health = self
+			.jsonrpsee_execute(|client| async move {
+				Ok(BizinikiwiSystemClient::<C>::health(&*client).await?)
+			})
+			.await
+			.map_err(|e| Error::failed_to_get_system_health::<C>(e))?;
+
+		let is_synced = !health.is_syncing && (!health.should_have_peers || health.peers > 0);
+		if is_synced {
+			Ok(())
+		} else {
+			Err(Error::ClientNotSynced(health))
+		}
+	}
+
+	async fn reconnect(&self) -> Result<()> {
+		let mut data = self.data.write().await;
+		let (tokio, client) = Self::build_client(&self.params).await?;
+		data.tokio = tokio;
+		data.client = client;
+		Ok(())
+	}
+
+	fn genesis_hash(&self) -> HashOf<C> {
+		self.genesis_hash
+	}
+
+	async fn header_hash_by_number(&self, number: BlockNumberOf<C>) -> Result<HashOf<C>> {
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiChainClient::<C>::block_hash(&*client, Some(number)).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_header_hash_by_number::<C>(number, e))
+	}
+
+	async fn header_by_hash(&self, hash: HashOf<C>) -> Result<HeaderOf<C>> {
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiChainClient::<C>::header(&*client, Some(hash)).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_header_by_hash::<C>(hash, e))
+	}
+
+	async fn block_by_hash(&self, hash: HashOf<C>) -> Result<SignedBlockOf<C>> {
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiChainClient::<C>::block(&*client, Some(hash)).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_block_by_hash::<C>(hash, e))
+	}
+
+	async fn best_finalized_header_hash(&self) -> Result<HashOf<C>> {
+		self.jsonrpsee_execute(|client| async move {
+			Ok(BizinikiwiChainClient::<C>::finalized_head(&*client).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_best_finalized_header_hash::<C>(e))
+	}
+
+	async fn best_header(&self) -> Result<HeaderOf<C>> {
+		self.jsonrpsee_execute(|client| async move {
+			Ok(BizinikiwiChainClient::<C>::header(&*client, None).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_best_header::<C>(e))
+	}
+
+	async fn subscribe_best_headers(&self) -> Result<Subscription<HeaderOf<C>>> {
+		self.subscribe_headers(
+			"best headers",
+			move |client| async move { BizinikiwiChainClient::<C>::subscribe_new_heads(&*client).await },
+			|e| Error::failed_to_subscribe_best_headers::<C>(e),
+		)
+		.await
+	}
+
+	async fn subscribe_finalized_headers(&self) -> Result<Subscription<HeaderOf<C>>> {
+		self.subscribe_headers(
+			"best finalized headers",
+			move |client| async move {
+				BizinikiwiChainClient::<C>::subscribe_finalized_heads(&*client).await
+			},
+			|e| Error::failed_to_subscribe_finalized_headers::<C>(e),
+		)
+		.await
+	}
+
+	async fn subscribe_grandpa_finality_justifications(&self) -> Result<Subscription<Bytes>>
+	where
+		C: ChainWithGrandpa,
+	{
+		self.subscribe_finality_justifications("GRANDPA", move |client| async move {
+			BizinikiwiGrandpaClient::<C>::subscribe_justifications(&*client).await
+		})
+		.await
+	}
+
+	async fn generate_grandpa_key_ownership_proof(
+		&self,
+		at: HashOf<C>,
+		set_id: pezsp_consensus_grandpa::SetId,
+		authority_id: pezsp_consensus_grandpa::AuthorityId,
+	) -> Result<Option<pezsp_consensus_grandpa::OpaqueKeyOwnershipProof>> {
+		self.state_call(
+			at,
+			SUB_API_GRANDPA_GENERATE_KEY_OWNERSHIP_PROOF.into(),
+			(set_id, authority_id),
+		)
+		.await
+	}
+
+	async fn subscribe_beefy_finality_justifications(&self) -> Result<Subscription<Bytes>> {
+		self.subscribe_finality_justifications("BEEFY", move |client| async move {
+			BizinikiwiBeefyClient::<C>::subscribe_justifications(&*client).await
+		})
+		.await
+	}
+
+	async fn token_decimals(&self) -> Result<Option<u64>> {
+		self.jsonrpsee_execute(move |client| async move {
+			let system_properties = BizinikiwiSystemClient::<C>::properties(&*client).await?;
+			Ok(system_properties.get("tokenDecimals").and_then(|v| v.as_u64()))
+		})
+		.await
+	}
+
+	async fn runtime_version(&self) -> Result<RuntimeVersion> {
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiStateClient::<C>::runtime_version(&*client).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_runtime_version::<C>(e))
+	}
+
+	async fn simple_runtime_version(&self) -> Result<SimpleRuntimeVersion> {
+		Ok(match self.params.chain_runtime_version {
+			ChainRuntimeVersion::Auto => {
+				let runtime_version = self.runtime_version().await?;
+				SimpleRuntimeVersion::from_runtime_version(&runtime_version)
+			},
+			ChainRuntimeVersion::Custom(ref version) => *version,
+		})
+	}
+
+	fn can_start_version_guard(&self) -> bool {
+		!matches!(self.params.chain_runtime_version, ChainRuntimeVersion::Auto)
+	}
+
+	async fn raw_storage_value(
+		&self,
+		at: HashOf<C>,
+		storage_key: StorageKey,
+	) -> Result<Option<StorageData>> {
+		let cloned_storage_key = storage_key.clone();
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiStateClient::<C>::storage(&*client, cloned_storage_key, Some(at)).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_read_storage_value::<C>(at, storage_key, e))
+	}
+
+	async fn pending_extrinsics(&self) -> Result<Vec<Bytes>> {
+		self.jsonrpsee_execute(move |client| async move {
+			Ok(BizinikiwiAuthorClient::<C>::pending_extrinsics(&*client).await?)
+		})
+		.await
+		.map_err(|e| Error::failed_to_get_pending_extrinsics::<C>(e))
+	}
+
+	async fn submit_unsigned_extrinsic(&self, transaction: Bytes) -> Result<HashOf<C>> {
+		// one last check that the transaction is valid. Most of checks happen in the relay loop and
+		// it is the "final" check before submission.
+		let best_header_hash = self.best_header_hash().await?;
+		self.validate_transaction(best_header_hash, PreEncoded(transaction.0.clone()))
+			.await
+			.map_err(|e| Error::failed_to_submit_transaction::<C>(e))?
+			.map_err(|e| Error::failed_to_submit_transaction::<C>(Error::TransactionInvalid(e)))?;
+
+		self.jsonrpsee_execute(move |client| async move {
+			let tx_hash = BizinikiwiAuthorClient::<C>::submit_extrinsic(&*client, transaction)
+				.await
+				.map_err(|e| {
+					tracing::error!(target: "bridge", error=?e, node=%C::NAME, "Failed to send transaction");
+					e
+				})?;
+			tracing::trace!(target: "bridge", node=%C::NAME, ?tx_hash, "Sent transaction");
+			Ok(tx_hash)
+		})
+		.await
+		.map_err(|e| Error::failed_to_submit_transaction::<C>(e))
+	}
+
+	async fn submit_signed_extrinsic(
+		&self,
+		signer: &AccountKeyPairOf<C>,
+		prepare_extrinsic: impl FnOnce(HeaderIdOf<C>, NonceOf<C>) -> Result<UnsignedTransaction<C>>
+			+ Send
+			+ 'static,
+	) -> Result<HashOf<C>>
+	where
+		C: ChainWithTransactions,
+		AccountIdOf<C>: From<<AccountKeyPairOf<C> as Pair>::Public>,
+	{
+		let _guard = self.submit_signed_extrinsic_lock.lock().await;
+		let transaction_nonce = self.next_account_index(signer.public().into()).await?;
+		let best_header = self.best_header().await?;
+		let signing_data = self.build_sign_params(signer.clone()).await?;
+
+		// By using parent of best block here, we are protecting again best-block reorganizations.
+		// E.g. transaction may have been submitted when the best block was `A[num=100]`. Then it
+		// has been changed to `B[num=100]`. Hash of `A` has been included into transaction
+		// signature payload. So when signature will be checked, the check will fail and transaction
+		// will be dropped from the pool.
+		let best_header_id = best_header.parent_id().unwrap_or_else(|| best_header.id());
+
+		let extrinsic = prepare_extrinsic(best_header_id, transaction_nonce)?;
+		let signed_extrinsic = C::sign_transaction(signing_data, extrinsic)?.encode();
+		self.submit_unsigned_extrinsic(Bytes(signed_extrinsic)).await
+	}
+
+	async fn submit_and_watch_signed_extrinsic(
+		&self,
+		signer: &AccountKeyPairOf<C>,
+		prepare_extrinsic: impl FnOnce(HeaderIdOf<C>, NonceOf<C>) -> Result<UnsignedTransaction<C>>
+			+ Send
+			+ 'static,
+	) -> Result<TransactionTracker<C, Self>>
+	where
+		C: ChainWithTransactions,
+		AccountIdOf<C>: From<<AccountKeyPairOf<C> as Pair>::Public>,
+	{
+		let self_clone = self.clone();
+		let signing_data = self.build_sign_params(signer.clone()).await?;
+		let _guard = self.submit_signed_extrinsic_lock.lock().await;
+		let transaction_nonce = self.next_account_index(signer.public().into()).await?;
+		let best_header = self.best_header().await?;
+		let best_header_id = best_header.id();
+
+		let extrinsic = prepare_extrinsic(best_header_id, transaction_nonce)?;
+		let stall_timeout = transaction_stall_timeout(
+			extrinsic.era.mortality_period(),
+			C::AVERAGE_BLOCK_INTERVAL,
+			STALL_TIMEOUT,
+		);
+		let signed_extrinsic = C::sign_transaction(signing_data, extrinsic)?.encode();
+
+		// one last check that the transaction is valid. Most of checks happen in the relay loop and
+		// it is the "final" check before submission.
+		self.validate_transaction(best_header_id.hash(), PreEncoded(signed_extrinsic.clone()))
+			.await
+			.map_err(|e| Error::failed_to_submit_transaction::<C>(e))?
+			.map_err(|e| Error::failed_to_submit_transaction::<C>(Error::TransactionInvalid(e)))?;
+
+		self.jsonrpsee_execute(move |client| async move {
+			let tx_hash = C::Hasher::hash(&signed_extrinsic);
+			let subscription: jsonrpsee::core::client::Subscription<_> =
+				BizinikiwiAuthorClient::<C>::submit_and_watch_extrinsic(
+					&*client,
+					Bytes(signed_extrinsic),
+				)
+				.await
+				.map_err(|e| {
+					tracing::error!(target: "bridge", error=?e, node=%C::NAME, "Failed to send transaction");
+					e
+				})?;
+			tracing::trace!(target: "bridge", node=%C::NAME, ?tx_hash, "Sent transaction");
+			Ok(TransactionTracker::new(
+				self_clone,
+				stall_timeout,
+				tx_hash,
+				Subscription::new_forwarded(
+					StreamDescription::new("transaction events".into(), C::NAME.into()),
+					subscription,
+				),
+			))
+		})
+		.await
+		.map_err(|e| Error::failed_to_submit_transaction::<C>(e))
+	}
+
+	async fn validate_transaction<SignedTransaction: Encode + Send + 'static>(
+		&self,
+		at: HashOf<C>,
+		transaction: SignedTransaction,
+	) -> Result<TransactionValidity> {
+		self.state_call(
+			at,
+			SUB_API_TXPOOL_VALIDATE_TRANSACTION.into(),
+			(TransactionSource::External, transaction, at),
+		)
+		.await
+	}
+
+	async fn estimate_extrinsic_weight<SignedTransaction: Encode + Send + 'static>(
+		&self,
+		at: HashOf<C>,
+		transaction: SignedTransaction,
+	) -> Result<Weight> {
+		let transaction_len = transaction.encoded_size() as u32;
+		let dispatch_info: RuntimeDispatchInfo<BalanceOf<C>> = self
+			.state_call(at, SUB_API_TX_PAYMENT_QUERY_INFO.into(), (transaction, transaction_len))
+			.await?;
+
+		Ok(dispatch_info.weight)
+	}
+
+	async fn raw_state_call<Args: Encode + Send>(
+		&self,
+		at: HashOf<C>,
+		method: String,
+		arguments: Args,
+	) -> Result<Bytes> {
+		let arguments = Bytes(arguments.encode());
+		let arguments_clone = arguments.clone();
+		let method_clone = method.clone();
+		self.jsonrpsee_execute(move |client| async move {
+			BizinikiwiStateClient::<C>::call(&*client, method, arguments, Some(at))
+				.await
+				.map_err(Into::into)
+		})
+		.await
+		.map_err(|e| Error::failed_state_call::<C>(at, method_clone, arguments_clone, e))
+	}
+
+	async fn prove_storage(
+		&self,
+		at: HashOf<C>,
+		keys: Vec<StorageKey>,
+	) -> Result<(StorageProof, HashOf<C>)> {
+		let state_root = *self.header_by_hash(at).await?.state_root();
+
+		let keys_clone = keys.clone();
+		let read_proof = self
+			.jsonrpsee_execute(move |client| async move {
+				BizinikiwiStateClient::<C>::prove_storage(&*client, keys_clone, Some(at))
+					.await
+					.map(|proof| StorageProof::new(proof.proof.into_iter().map(|b| b.0)))
+					.map_err(Into::into)
+			})
+			.await
+			.map_err(|e| Error::failed_to_prove_storage::<C>(at, keys.clone(), e))?;
+
+		Ok((read_proof, state_root))
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::{guard::tests::TestEnvironment, test_chain::TestChain};
+	use futures::{channel::mpsc::unbounded, FutureExt, SinkExt, StreamExt};
+
+	async fn run_ensure_correct_runtime_version(
+		expected: ChainRuntimeVersion,
+		actual: RuntimeVersion,
+	) -> Result<()> {
+		let (
+			(mut runtime_version_tx, runtime_version_rx),
+			(slept_tx, _slept_rx),
+			(aborted_tx, mut aborted_rx),
+		) = (unbounded(), unbounded(), unbounded());
+		runtime_version_tx.send(actual).await.unwrap();
+		let mut env = TestEnvironment { runtime_version_rx, slept_tx, aborted_tx };
+
+		let ensure_correct_runtime_version =
+			RpcClient::<TestChain>::ensure_correct_runtime_version(&mut env, expected).boxed();
+		let aborted = aborted_rx.next().map(|_| Err(Error::Custom("".into()))).boxed();
+		futures::pin_mut!(ensure_correct_runtime_version, aborted);
+		futures::future::select(ensure_correct_runtime_version, aborted)
+			.await
+			.into_inner()
+			.0
+	}
+
+	#[async_std::test]
+	async fn ensure_correct_runtime_version_works() {
+		// when we are configured to use auto version
+		assert!(matches!(
+			run_ensure_correct_runtime_version(
+				ChainRuntimeVersion::Auto,
+				RuntimeVersion {
+					spec_version: 100,
+					transaction_version: 100,
+					..Default::default()
+				},
+			)
+			.await,
+			Ok(()),
+		));
+		// when actual == expected
+		assert!(matches!(
+			run_ensure_correct_runtime_version(
+				ChainRuntimeVersion::Custom(SimpleRuntimeVersion {
+					spec_version: 100,
+					transaction_version: 100
+				}),
+				RuntimeVersion {
+					spec_version: 100,
+					transaction_version: 100,
+					..Default::default()
+				},
+			)
+			.await,
+			Ok(()),
+		));
+		// when actual spec version < expected spec version
+		assert!(matches!(
+			run_ensure_correct_runtime_version(
+				ChainRuntimeVersion::Custom(SimpleRuntimeVersion {
+					spec_version: 100,
+					transaction_version: 100
+				}),
+				RuntimeVersion { spec_version: 99, transaction_version: 100, ..Default::default() },
+			)
+			.await,
+			Err(Error::WaitingForRuntimeUpgrade {
+				expected: SimpleRuntimeVersion { spec_version: 100, transaction_version: 100 },
+				actual: SimpleRuntimeVersion { spec_version: 99, transaction_version: 100 },
+				..
+			}),
+		));
+		// when actual spec version > expected spec version
+		assert!(matches!(
+			run_ensure_correct_runtime_version(
+				ChainRuntimeVersion::Custom(SimpleRuntimeVersion {
+					spec_version: 100,
+					transaction_version: 100
+				}),
+				RuntimeVersion {
+					spec_version: 101,
+					transaction_version: 100,
+					..Default::default()
+				},
+			)
+			.await,
+			Err(Error::Custom(_)),
+		));
+	}
+}

pezbridges/relays/client-bizinikiwi/src/client/rpc_api.rs

@@ -0,0 +1,152 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! The most generic Bizinikiwi node RPC interface.
+
+use crate::{Chain, ChainWithGrandpa, TransactionStatusOf};
+
+use jsonrpsee::proc_macros::rpc;
+use pezpallet_transaction_payment_rpc_runtime_api::FeeDetails;
+use pezsc_rpc_api::{state::ReadProof, system::Health};
+use pezsp_core::{
+	storage::{StorageData, StorageKey},
+	Bytes,
+};
+use pezsp_rpc::number::NumberOrHex;
+use pezsp_version::RuntimeVersion;
+
+/// RPC methods of Bizinikiwi `system` namespace, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "system")]
+pub(crate) trait BizinikiwiSystem<C> {
+	/// Return node health.
+	#[method(name = "health")]
+	async fn health(&self) -> RpcResult<Health>;
+	/// Return system properties.
+	#[method(name = "properties")]
+	async fn properties(&self) -> RpcResult<pezsc_chain_spec::Properties>;
+}
+
+/// RPC methods of Bizinikiwi `chain` namespace, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "chain")]
+pub(crate) trait BizinikiwiChain<C> {
+	/// Get block hash by its number.
+	#[method(name = "getBlockHash")]
+	async fn block_hash(&self, block_number: Option<C::BlockNumber>) -> RpcResult<C::Hash>;
+	/// Return block header by its hash.
+	#[method(name = "getHeader")]
+	async fn header(&self, block_hash: Option<C::Hash>) -> RpcResult<C::Header>;
+	/// Return best finalized block hash.
+	#[method(name = "getFinalizedHead")]
+	async fn finalized_head(&self) -> RpcResult<C::Hash>;
+	/// Return signed block (with justifications) by its hash.
+	#[method(name = "getBlock")]
+	async fn block(&self, block_hash: Option<C::Hash>) -> RpcResult<C::SignedBlock>;
+	/// Subscribe to best headers.
+	#[subscription(
+		name = "subscribeNewHeads" => "newHead",
+		unsubscribe = "unsubscribeNewHeads",
+		item = C::Header
+	)]
+	async fn subscribe_new_heads(&self);
+	/// Subscribe to finalized headers.
+	#[subscription(
+		name = "subscribeFinalizedHeads" => "finalizedHead",
+		unsubscribe = "unsubscribeFinalizedHeads",
+		item = C::Header
+	)]
+	async fn subscribe_finalized_heads(&self);
+}
+
+/// RPC methods of Bizinikiwi `author` namespace, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "author")]
+pub(crate) trait BizinikiwiAuthor<C> {
+	/// Submit extrinsic to the transaction pool.
+	#[method(name = "submitExtrinsic")]
+	async fn submit_extrinsic(&self, extrinsic: Bytes) -> RpcResult<C::Hash>;
+	/// Return vector of pending extrinsics from the transaction pool.
+	#[method(name = "pendingExtrinsics")]
+	async fn pending_extrinsics(&self) -> RpcResult<Vec<Bytes>>;
+	/// Submit and watch for extrinsic state.
+	#[subscription(name = "submitAndWatchExtrinsic", unsubscribe = "unwatchExtrinsic", item = TransactionStatusOf<C>)]
+	async fn submit_and_watch_extrinsic(&self, extrinsic: Bytes);
+}
+
+/// RPC methods of Bizinikiwi `state` namespace, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "state")]
+pub(crate) trait BizinikiwiState<C> {
+	/// Get current runtime version.
+	#[method(name = "getRuntimeVersion")]
+	async fn runtime_version(&self) -> RpcResult<RuntimeVersion>;
+	/// Call given runtime method.
+	#[method(name = "call")]
+	async fn call(
+		&self,
+		method: String,
+		data: Bytes,
+		at_block: Option<C::Hash>,
+	) -> RpcResult<Bytes>;
+	/// Get value of the runtime storage.
+	#[method(name = "getStorage")]
+	async fn storage(
+		&self,
+		key: StorageKey,
+		at_block: Option<C::Hash>,
+	) -> RpcResult<Option<StorageData>>;
+	/// Get proof of the runtime storage value.
+	#[method(name = "getReadProof")]
+	async fn prove_storage(
+		&self,
+		keys: Vec<StorageKey>,
+		hash: Option<C::Hash>,
+	) -> RpcResult<ReadProof<C::Hash>>;
+}
+
+/// RPC methods of Bizinikiwi `grandpa` namespace, that we are using.
+#[rpc(client, client_bounds(C: ChainWithGrandpa), namespace = "grandpa")]
+pub(crate) trait BizinikiwiGrandpa<C> {
+	/// Subscribe to GRANDPA justifications.
+	#[subscription(name = "subscribeJustifications", unsubscribe = "unsubscribeJustifications", item = Bytes)]
+	async fn subscribe_justifications(&self);
+}
+
+// TODO: Use `ChainWithBeefy` instead of `Chain` after #1606 is merged
+/// RPC methods of Bizinikiwi `beefy` namespace, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "beefy")]
+pub(crate) trait BizinikiwiBeefy<C> {
+	/// Subscribe to BEEFY justifications.
+	#[subscription(name = "subscribeJustifications", unsubscribe = "unsubscribeJustifications", item = Bytes)]
+	async fn subscribe_justifications(&self);
+}
+
+/// RPC methods of Bizinikiwi `system` frame pezpallet, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "system")]
+pub(crate) trait BizinikiwiFrameSystem<C> {
+	/// Return index of next account transaction.
+	#[method(name = "accountNextIndex")]
+	async fn account_next_index(&self, account_id: C::AccountId) -> RpcResult<C::Nonce>;
+}
+
+/// RPC methods of Bizinikiwi `pezpallet_transaction_payment` frame pezpallet, that we are using.
+#[rpc(client, client_bounds(C: Chain), namespace = "payment")]
+pub(crate) trait BizinikiwiTransactionPayment<C> {
+	/// Query transaction fee details.
+	#[method(name = "queryFeeDetails")]
+	async fn fee_details(
+		&self,
+		extrinsic: Bytes,
+		at_block: Option<C::Hash>,
+	) -> RpcResult<FeeDetails<NumberOrHex>>;
+}

pezbridges/relays/client-bizinikiwi/src/client/subscription.rs

@@ -0,0 +1,238 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::error::Result as ClientResult;
+
+use async_std::{
+	channel::{bounded, Receiver, Sender},
+	stream::StreamExt,
+};
+use futures::{FutureExt, Stream};
+use pezsp_runtime::DeserializeOwned;
+use std::{
+	fmt::Debug,
+	pin::Pin,
+	result::Result as StdResult,
+	task::{Context, Poll},
+};
+
+/// Once channel reaches this capacity, the subscription breaks.
+const CHANNEL_CAPACITY: usize = 128;
+
+/// Structure describing a stream.
+#[derive(Clone)]
+pub struct StreamDescription {
+	stream_name: String,
+	chain_name: String,
+}
+
+impl StreamDescription {
+	/// Create a new instance of `StreamDescription`.
+	pub fn new(stream_name: String, chain_name: String) -> Self {
+		Self { stream_name, chain_name }
+	}
+
+	/// Get a stream description.
+	fn get(&self) -> String {
+		format!("{} stream of {}", self.stream_name, self.chain_name)
+	}
+}
+
+/// Chainable stream that transforms items of type `Result<T, E>` to items of type `T`.
+///
+/// If it encounters an item of type `Err`, it returns `Poll::Ready(None)`
+/// and terminates the underlying stream.
+struct Unwrap<S: Stream<Item = StdResult<T, E>>, T, E> {
+	desc: StreamDescription,
+	stream: Option<S>,
+}
+
+impl<S: Stream<Item = StdResult<T, E>>, T, E> Unwrap<S, T, E> {
+	/// Create a new instance of `Unwrap`.
+	pub fn new(desc: StreamDescription, stream: S) -> Self {
+		Self { desc, stream: Some(stream) }
+	}
+}
+
+impl<S: Stream<Item = StdResult<T, E>> + Unpin, T: DeserializeOwned, E: Debug> Stream
+	for Unwrap<S, T, E>
+{
+	type Item = T;
+
+	fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+		Poll::Ready(match self.stream.as_mut() {
+			Some(subscription) => match futures::ready!(Pin::new(subscription).poll_next(cx)) {
+				Some(Ok(item)) => Some(item),
+				Some(Err(e)) => {
+					self.stream.take();
+					tracing::debug!(
+						target: "bridge",
+						error=?e,
+						desc=%self.desc.get(),
+						"Returned with error. It may need to be restarted"
+					);
+					None
+				},
+				None => {
+					self.stream.take();
+					tracing::debug!(
+						target: "bridge",
+						desc=%self.desc.get(),
+						"Returned `None`. It may need to be restarted"
+					);
+					None
+				},
+			},
+			None => None,
+		})
+	}
+}
+
+/// Subscription factory that produces subscriptions, sharing the same background thread.
+#[derive(Clone)]
+pub struct SubscriptionBroadcaster<T> {
+	desc: StreamDescription,
+	subscribers_sender: Sender<Sender<T>>,
+}
+
+impl<T: 'static + Clone + DeserializeOwned + Send> SubscriptionBroadcaster<T> {
+	/// Create new subscription factory.
+	pub fn new(subscription: Subscription<T>) -> StdResult<Self, Subscription<T>> {
+		// It doesn't make sense to further broadcast a broadcasted subscription.
+		if subscription.is_broadcasted {
+			return Err(subscription);
+		}
+
+		let desc = subscription.desc().clone();
+		let (subscribers_sender, subscribers_receiver) = bounded(CHANNEL_CAPACITY);
+		async_std::task::spawn(background_worker(subscription, subscribers_receiver));
+		Ok(Self { desc, subscribers_sender })
+	}
+
+	/// Produce new subscription.
+	pub async fn subscribe(&self) -> ClientResult<Subscription<T>> {
+		let (items_sender, items_receiver) = bounded(CHANNEL_CAPACITY);
+		self.subscribers_sender.try_send(items_sender)?;
+
+		Ok(Subscription::new_broadcasted(self.desc.clone(), items_receiver))
+	}
+}
+
+/// Subscription to some chain events.
+pub struct Subscription<T> {
+	desc: StreamDescription,
+	subscription: Box<dyn Stream<Item = T> + Unpin + Send>,
+	is_broadcasted: bool,
+}
+
+impl<T: 'static + Clone + DeserializeOwned + Send> Subscription<T> {
+	/// Create new forwarded subscription.
+	pub fn new_forwarded(
+		desc: StreamDescription,
+		subscription: impl Stream<Item = StdResult<T, serde_json::Error>> + Unpin + Send + 'static,
+	) -> Self {
+		Self {
+			desc: desc.clone(),
+			subscription: Box::new(Unwrap::new(desc, subscription)),
+			is_broadcasted: false,
+		}
+	}
+
+	/// Create new broadcasted subscription.
+	pub fn new_broadcasted(
+		desc: StreamDescription,
+		subscription: impl Stream<Item = T> + Unpin + Send + 'static,
+	) -> Self {
+		Self { desc, subscription: Box::new(subscription), is_broadcasted: true }
+	}
+
+	/// Get the description of the underlying stream
+	pub fn desc(&self) -> &StreamDescription {
+		&self.desc
+	}
+}
+
+impl<T> Stream for Subscription<T> {
+	type Item = T;
+
+	fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+		Poll::Ready(futures::ready!(Pin::new(&mut self.subscription).poll_next(cx)))
+	}
+}
+
+/// Background worker that is executed in tokio context as `jsonrpsee` requires.
+///
+/// This task may exit under some circumstances. It'll send the correspondent
+/// message (`Err` or `None`) to all known listeners. Also, when it stops, all
+/// subsequent reads and new subscribers will get the connection error (`ChannelError`).
+async fn background_worker<T: 'static + Clone + DeserializeOwned + Send>(
+	mut subscription: Subscription<T>,
+	mut subscribers_receiver: Receiver<Sender<T>>,
+) {
+	fn log_task_exit(desc: &StreamDescription, reason: &str) {
+		tracing::debug!(
+			target: "bridge",
+			desc=%desc.get(),
+			%reason,
+			"Background task of subscription broadcaster has stopped"
+		);
+	}
+
+	// wait for first subscriber until actually starting subscription
+	let subscriber = match subscribers_receiver.next().await {
+		Some(subscriber) => subscriber,
+		None => {
+			// it means that the last subscriber/factory has been dropped, so we need to
+			// exit too
+			return log_task_exit(subscription.desc(), "client has stopped");
+		},
+	};
+
+	// actually subscribe
+	let mut subscribers = vec![subscriber];
+
+	// start listening for new items and receivers
+	loop {
+		futures::select! {
+			subscriber = subscribers_receiver.next().fuse() => {
+				match subscriber {
+					Some(subscriber) => subscribers.push(subscriber),
+					None => {
+						// it means that the last subscriber/factory has been dropped, so we need to
+						// exit too
+						return log_task_exit(subscription.desc(), "client has stopped")
+					},
+				}
+			},
+			maybe_item = subscription.subscription.next().fuse() => {
+				match maybe_item {
+					Some(item) => {
+						// notify subscribers
+						subscribers.retain(|subscriber| {
+							let send_result = subscriber.try_send(item.clone());
+							send_result.is_ok()
+						});
+					}
+					None => {
+						// The underlying client has dropped, so we can't do anything here
+						// and need to stop the task.
+						return log_task_exit(subscription.desc(), "stream has finished");
+					}
+				}
+			},
+		}
+	}
+}

pezbridges/relays/client-bizinikiwi/src/client/traits.rs

@@ -0,0 +1,234 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::{
+	error::{Error, Result},
+	AccountIdOf, AccountKeyPairOf, BlockNumberOf, Chain, ChainWithGrandpa, ChainWithTransactions,
+	HashOf, HeaderIdOf, HeaderOf, NonceOf, SignedBlockOf, SimpleRuntimeVersion, Subscription,
+	TransactionTracker, UnsignedTransaction,
+};
+
+use async_trait::async_trait;
+use pezbp_runtime::{StorageDoubleMapKeyProvider, StorageMapKeyProvider};
+use codec::{Decode, Encode};
+use pezframe_support::weights::Weight;
+use pezsp_core::{
+	storage::{StorageData, StorageKey},
+	Bytes, Pair,
+};
+use pezsp_runtime::{traits::Header as _, transaction_validity::TransactionValidity};
+use pezsp_trie::StorageProof;
+use pezsp_version::RuntimeVersion;
+use std::fmt::Debug;
+
+/// Relay uses the `Client` to communicate with the node, connected to Bizinikiwi
+/// chain `C`.
+#[async_trait]
+pub trait Client<C: Chain>: 'static + Send + Sync + Clone + Debug {
+	/// Returns error if client has no connected peers or it believes it is far
+	/// behind the chain tip.
+	async fn ensure_synced(&self) -> Result<()>;
+	/// Reconnects the client.
+	async fn reconnect(&self) -> Result<()>;
+
+	/// Return hash of the genesis block.
+	fn genesis_hash(&self) -> HashOf<C>;
+	/// Get header hash by number.
+	async fn header_hash_by_number(&self, number: BlockNumberOf<C>) -> Result<HashOf<C>>;
+	/// Get header by hash.
+	async fn header_by_hash(&self, hash: HashOf<C>) -> Result<HeaderOf<C>>;
+	/// Get header by number.
+	async fn header_by_number(&self, number: BlockNumberOf<C>) -> Result<HeaderOf<C>> {
+		self.header_by_hash(self.header_hash_by_number(number).await?).await
+	}
+	/// Get block by hash.
+	async fn block_by_hash(&self, hash: HashOf<C>) -> Result<SignedBlockOf<C>>;
+
+	/// Get best finalized header hash.
+	async fn best_finalized_header_hash(&self) -> Result<HashOf<C>>;
+	/// Get best finalized header number.
+	async fn best_finalized_header_number(&self) -> Result<BlockNumberOf<C>> {
+		Ok(*self.best_finalized_header().await?.number())
+	}
+	/// Get best finalized header.
+	async fn best_finalized_header(&self) -> Result<HeaderOf<C>> {
+		self.header_by_hash(self.best_finalized_header_hash().await?).await
+	}
+
+	/// Get best header.
+	async fn best_header(&self) -> Result<HeaderOf<C>>;
+	/// Get best header hash.
+	async fn best_header_hash(&self) -> Result<HashOf<C>> {
+		Ok(self.best_header().await?.hash())
+	}
+
+	/// Subscribe to new best headers.
+	async fn subscribe_best_headers(&self) -> Result<Subscription<HeaderOf<C>>>;
+	/// Subscribe to new finalized headers.
+	async fn subscribe_finalized_headers(&self) -> Result<Subscription<HeaderOf<C>>>;
+
+	/// Subscribe to GRANDPA finality justifications.
+	async fn subscribe_grandpa_finality_justifications(&self) -> Result<Subscription<Bytes>>
+	where
+		C: ChainWithGrandpa;
+	/// Generates a proof of key ownership for the given authority in the given set.
+	async fn generate_grandpa_key_ownership_proof(
+		&self,
+		at: HashOf<C>,
+		set_id: pezsp_consensus_grandpa::SetId,
+		authority_id: pezsp_consensus_grandpa::AuthorityId,
+	) -> Result<Option<pezsp_consensus_grandpa::OpaqueKeyOwnershipProof>>;
+
+	/// Subscribe to BEEFY finality justifications.
+	async fn subscribe_beefy_finality_justifications(&self) -> Result<Subscription<Bytes>>;
+
+	/// Return `tokenDecimals` property from the set of chain properties.
+	async fn token_decimals(&self) -> Result<Option<u64>>;
+	/// Get runtime version of the connected chain.
+	async fn runtime_version(&self) -> Result<RuntimeVersion>;
+	/// Get partial runtime version, to use when signing transactions.
+	async fn simple_runtime_version(&self) -> Result<SimpleRuntimeVersion>;
+	/// Returns `true` if version guard can be started.
+	///
+	/// There's no reason to run version guard when version mode is set to `Auto`. It can
+	/// lead to relay shutdown when chain is upgraded, even though we have explicitly
+	/// said that we don't want to shutdown.
+	fn can_start_version_guard(&self) -> bool;
+
+	/// Read raw value from runtime storage.
+	async fn raw_storage_value(
+		&self,
+		at: HashOf<C>,
+		storage_key: StorageKey,
+	) -> Result<Option<StorageData>>;
+	/// Read and decode value from runtime storage.
+	async fn storage_value<T: Decode + 'static>(
+		&self,
+		at: HashOf<C>,
+		storage_key: StorageKey,
+	) -> Result<Option<T>> {
+		self.raw_storage_value(at, storage_key.clone())
+			.await?
+			.map(|encoded_value| {
+				T::decode(&mut &encoded_value.0[..]).map_err(|e| {
+					Error::failed_to_read_storage_value::<C>(at, storage_key, e.into())
+				})
+			})
+			.transpose()
+	}
+	/// Read and decode value from runtime storage map.
+	///
+	/// `pezpallet_prefix` is the name of the pezpallet (used in `construct_runtime`), which
+	/// "contains" the storage map.
+	async fn storage_map_value<T: StorageMapKeyProvider>(
+		&self,
+		at: HashOf<C>,
+		pezpallet_prefix: &str,
+		storage_key: &T::Key,
+	) -> Result<Option<T::Value>> {
+		self.storage_value(at, T::final_key(pezpallet_prefix, storage_key)).await
+	}
+	/// Read and decode value from runtime storage double map.
+	///
+	/// `pezpallet_prefix` is the name of the pezpallet (used in `construct_runtime`), which
+	/// "contains" the storage double map.
+	async fn storage_double_map_value<T: StorageDoubleMapKeyProvider>(
+		&self,
+		at: HashOf<C>,
+		pezpallet_prefix: &str,
+		key1: &T::Key1,
+		key2: &T::Key2,
+	) -> Result<Option<T::Value>> {
+		self.storage_value(at, T::final_key(pezpallet_prefix, key1, key2)).await
+	}
+
+	/// Returns pending extrinsics from transaction pool.
+	async fn pending_extrinsics(&self) -> Result<Vec<Bytes>>;
+	/// Submit unsigned extrinsic for inclusion in a block.
+	///
+	/// Note: The given transaction needs to be SCALE encoded beforehand.
+	async fn submit_unsigned_extrinsic(&self, transaction: Bytes) -> Result<HashOf<C>>;
+	/// Submit an extrinsic signed by given account.
+	///
+	/// All calls of this method are synchronized, so there can't be more than one active
+	/// `submit_signed_extrinsic()` call. This guarantees that no nonces collision may happen
+	/// if all client instances are clones of the same initial `Client`.
+	///
+	/// Note: The given transaction needs to be SCALE encoded beforehand.
+	async fn submit_signed_extrinsic(
+		&self,
+		signer: &AccountKeyPairOf<C>,
+		prepare_extrinsic: impl FnOnce(HeaderIdOf<C>, NonceOf<C>) -> Result<UnsignedTransaction<C>>
+			+ Send
+			+ 'static,
+	) -> Result<HashOf<C>>
+	where
+		C: ChainWithTransactions,
+		AccountIdOf<C>: From<<AccountKeyPairOf<C> as Pair>::Public>;
+	/// Does exactly the same as `submit_signed_extrinsic`, but keeps watching for extrinsic status
+	/// after submission.
+	async fn submit_and_watch_signed_extrinsic(
+		&self,
+		signer: &AccountKeyPairOf<C>,
+		prepare_extrinsic: impl FnOnce(HeaderIdOf<C>, NonceOf<C>) -> Result<UnsignedTransaction<C>>
+			+ Send
+			+ 'static,
+	) -> Result<TransactionTracker<C, Self>>
+	where
+		C: ChainWithTransactions,
+		AccountIdOf<C>: From<<AccountKeyPairOf<C> as Pair>::Public>;
+	/// Validate transaction at given block.
+	async fn validate_transaction<SignedTransaction: Encode + Send + 'static>(
+		&self,
+		at: HashOf<C>,
+		transaction: SignedTransaction,
+	) -> Result<TransactionValidity>;
+	/// Returns weight of the given transaction.
+	async fn estimate_extrinsic_weight<SignedTransaction: Encode + Send + 'static>(
+		&self,
+		at: HashOf<C>,
+		transaction: SignedTransaction,
+	) -> Result<Weight>;
+
+	/// Execute runtime call at given block.
+	async fn raw_state_call<Args: Encode + Send>(
+		&self,
+		at: HashOf<C>,
+		method: String,
+		arguments: Args,
+	) -> Result<Bytes>;
+	/// Execute runtime call at given block, provided the input and output types.
+	/// It also performs the input encode and output decode.
+	async fn state_call<Args: Encode + Send, Ret: Decode>(
+		&self,
+		at: HashOf<C>,
+		method: String,
+		arguments: Args,
+	) -> Result<Ret> {
+		let encoded_arguments = arguments.encode();
+		let encoded_output = self.raw_state_call(at, method.clone(), arguments).await?;
+		Ret::decode(&mut &encoded_output.0[..]).map_err(|e| {
+			Error::failed_state_call::<C>(at, method, Bytes(encoded_arguments), e.into())
+		})
+	}
+
+	/// Returns storage proof of given storage keys and state root.
+	async fn prove_storage(
+		&self,
+		at: HashOf<C>,
+		keys: Vec<StorageKey>,
+	) -> Result<(StorageProof, HashOf<C>)>;
+}

pezbridges/relays/client-bizinikiwi/src/error.rs

@@ -0,0 +1,431 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Bizinikiwi node RPC errors.
+
+use crate::{BlockNumberOf, Chain, HashOf, SimpleRuntimeVersion};
+use bp_header_pez_chain::SubmitFinalityProofCallExtras;
+use bp_pezkuwi_core::teyrchains::ParaId;
+use jsonrpsee::core::ClientError as RpcError;
+use relay_utils::MaybeConnectionError;
+use pezsc_rpc_api::system::Health;
+use pezsp_core::{storage::StorageKey, Bytes};
+use pezsp_runtime::transaction_validity::TransactionValidityError;
+use thiserror::Error;
+
+/// Result type used by Bizinikiwi client.
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Errors that can occur only when interacting with
+/// a Bizinikiwi node through RPC.
+#[derive(Error, Debug)]
+pub enum Error {
+	/// IO error.
+	#[error("IO error: {0}")]
+	Io(#[from] std::io::Error),
+	/// An error that can occur when making a request to
+	/// an JSON-RPC server.
+	#[error("RPC error: {0}")]
+	RpcError(#[from] RpcError),
+	/// The response from the server could not be SCALE decoded.
+	#[error("Response parse failed: {0}")]
+	ResponseParseFailed(#[from] codec::Error),
+	/// Internal channel error - communication channel is either closed, or full.
+	/// It can be solved with reconnect.
+	#[error("Internal communication channel error: {0:?}.")]
+	ChannelError(String),
+	/// Required teyrchain head is not present at the relay chain.
+	#[error("Teyrchain {0:?} head {1} is missing from the relay chain storage.")]
+	MissingRequiredTeyrchainHead(ParaId, u64),
+	/// Failed to find finality proof for the given header.
+	#[error("Failed to find finality proof for header {0}.")]
+	FinalityProofNotFound(u64),
+	/// The client we're connected to is not synced, so we can't rely on its state.
+	#[error("Bizinikiwi client is not synced {0}.")]
+	ClientNotSynced(Health),
+	/// Failed to get system health.
+	#[error("Failed to get system health of {chain} node: {error:?}.")]
+	FailedToGetSystemHealth {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read best finalized header hash from given chain.
+	#[error("Failed to read best finalized header hash of {chain}: {error:?}.")]
+	FailedToReadBestFinalizedHeaderHash {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read best finalized header from given chain.
+	#[error("Failed to read best header of {chain}: {error:?}.")]
+	FailedToReadBestHeader {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read header hash by number from given chain.
+	#[error("Failed to read header hash by number {number} of {chain}: {error:?}.")]
+	FailedToReadHeaderHashByNumber {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Number of the header we've tried to read.
+		number: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read header by hash from given chain.
+	#[error("Failed to read header {hash} of {chain}: {error:?}.")]
+	FailedToReadHeaderByHash {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Hash of the header we've tried to read.
+		hash: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read block by hash from given chain.
+	#[error("Failed to read block {hash} of {chain}: {error:?}.")]
+	FailedToReadBlockByHash {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Hash of the header we've tried to read.
+		hash: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read sotrage value at given chain.
+	#[error("Failed to read storage value {key:?} at {chain}: {error:?}.")]
+	FailedToReadStorageValue {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Hash of the block we've tried to read value from.
+		hash: String,
+		/// Runtime storage key
+		key: StorageKey,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to read runtime version of given chain.
+	#[error("Failed to read runtime version of {chain}: {error:?}.")]
+	FailedToReadRuntimeVersion {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to get pending extrinsics.
+	#[error("Failed to get pending extrinsics of {chain}: {error:?}.")]
+	FailedToGetPendingExtrinsics {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to submit transaction.
+	#[error("Failed to submit {chain} transaction: {error:?}.")]
+	FailedToSubmitTransaction {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Runtime call has failed.
+	#[error("Runtime call {method} with arguments {arguments:?} of chain {chain} at {hash} has failed: {error:?}.")]
+	FailedStateCall {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Hash of the block we've tried to call at.
+		hash: String,
+		/// Runtime API method.
+		method: String,
+		/// Encoded method arguments.
+		arguments: Bytes,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to prove storage keys.
+	#[error("Failed to prove storage keys {storage_keys:?} of {chain} at {hash}: {error:?}.")]
+	FailedToProveStorage {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Hash of the block we've tried to prove keys at.
+		hash: String,
+		/// Storage keys we have tried to prove.
+		storage_keys: Vec<StorageKey>,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to subscribe to GRANDPA justifications stream.
+	#[error("Failed to subscribe to {chain} best headers: {error:?}.")]
+	FailedToSubscribeBestHeaders {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to subscribe to GRANDPA justifications stream.
+	#[error("Failed to subscribe to {chain} finalized headers: {error:?}.")]
+	FailedToSubscribeFinalizedHeaders {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Failed to subscribe to GRANDPA justifications stream.
+	#[error("Failed to subscribe to {chain} justifications: {error:?}.")]
+	FailedToSubscribeJustifications {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Underlying error.
+		error: Box<Error>,
+	},
+	/// Headers of the chain are finalized out of order. Maybe chain has been
+	/// restarted?
+	#[error("Finalized headers of {chain} are unordered: previously finalized {prev_number} vs new {next_number}")]
+	UnorderedFinalizedHeaders {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Previously finalized header number.
+		prev_number: String,
+		/// New finalized header number.
+		next_number: String,
+	},
+	/// The bridge pezpallet is halted and all transactions will be rejected.
+	#[error("Bridge pezpallet is halted.")]
+	BridgePalletIsHalted,
+	/// The bridge pezpallet is not yet initialized and all transactions will be rejected.
+	#[error("Bridge pezpallet is not initialized.")]
+	BridgePalletIsNotInitialized,
+	/// The Bizinikiwi transaction is invalid.
+	#[error("Bizinikiwi transaction is invalid: {0:?}")]
+	TransactionInvalid(#[from] TransactionValidityError),
+	/// The client is configured to use newer runtime version than the connected chain uses.
+	/// The client will keep waiting until chain is upgraded to given version.
+	#[error("Waiting for {chain} runtime upgrade: expected {expected:?} actual {actual:?}")]
+	WaitingForRuntimeUpgrade {
+		/// Name of the chain where the error has happened.
+		chain: String,
+		/// Expected runtime version.
+		expected: SimpleRuntimeVersion,
+		/// Actual runtime version.
+		actual: SimpleRuntimeVersion,
+	},
+	/// Finality proof submission exceeds size and/or weight limits.
+	#[error("Finality proof submission exceeds limits: {extras:?}")]
+	FinalityProofWeightLimitExceeded {
+		/// Finality proof submission extras.
+		extras: SubmitFinalityProofCallExtras,
+	},
+	/// Custom logic error.
+	#[error("{0}")]
+	Custom(String),
+}
+
+impl From<tokio::task::JoinError> for Error {
+	fn from(error: tokio::task::JoinError) -> Self {
+		Error::ChannelError(format!("failed to wait tokio task: {error}"))
+	}
+}
+
+impl<T> From<async_std::channel::TrySendError<T>> for Error {
+	fn from(error: async_std::channel::TrySendError<T>) -> Self {
+		Error::ChannelError(format!("`try_send` has failed: {error:?}"))
+	}
+}
+
+impl From<async_std::channel::RecvError> for Error {
+	fn from(error: async_std::channel::RecvError) -> Self {
+		Error::ChannelError(format!("`recv` has failed: {error:?}"))
+	}
+}
+
+impl Error {
+	/// Box the error.
+	pub fn boxed(self) -> Box<Self> {
+		Box::new(self)
+	}
+
+	/// Returns nested error reference.
+	pub fn nested(&self) -> Option<&Self> {
+		match *self {
+			Self::FailedToReadBestFinalizedHeaderHash { ref error, .. } => Some(&**error),
+			Self::FailedToReadBestHeader { ref error, .. } => Some(&**error),
+			Self::FailedToReadHeaderHashByNumber { ref error, .. } => Some(&**error),
+			Self::FailedToReadHeaderByHash { ref error, .. } => Some(&**error),
+			Self::FailedToReadBlockByHash { ref error, .. } => Some(&**error),
+			Self::FailedToReadStorageValue { ref error, .. } => Some(&**error),
+			Self::FailedToReadRuntimeVersion { ref error, .. } => Some(&**error),
+			Self::FailedToGetPendingExtrinsics { ref error, .. } => Some(&**error),
+			Self::FailedToSubmitTransaction { ref error, .. } => Some(&**error),
+			Self::FailedStateCall { ref error, .. } => Some(&**error),
+			Self::FailedToProveStorage { ref error, .. } => Some(&**error),
+			Self::FailedToGetSystemHealth { ref error, .. } => Some(&**error),
+			Self::FailedToSubscribeBestHeaders { ref error, .. } => Some(&**error),
+			Self::FailedToSubscribeFinalizedHeaders { ref error, .. } => Some(&**error),
+			Self::FailedToSubscribeJustifications { ref error, .. } => Some(&**error),
+			_ => None,
+		}
+	}
+
+	/// Constructs `FailedToReadHeaderHashByNumber` variant.
+	pub fn failed_to_read_header_hash_by_number<C: Chain>(
+		number: BlockNumberOf<C>,
+		e: Error,
+	) -> Self {
+		Error::FailedToReadHeaderHashByNumber {
+			chain: C::NAME.into(),
+			number: format!("{number}"),
+			error: e.boxed(),
+		}
+	}
+
+	/// Constructs `FailedToReadHeaderByHash` variant.
+	pub fn failed_to_read_header_by_hash<C: Chain>(hash: HashOf<C>, e: Error) -> Self {
+		Error::FailedToReadHeaderByHash {
+			chain: C::NAME.into(),
+			hash: format!("{hash}"),
+			error: e.boxed(),
+		}
+	}
+
+	/// Constructs `FailedToReadBlockByHash` variant.
+	pub fn failed_to_read_block_by_hash<C: Chain>(hash: HashOf<C>, e: Error) -> Self {
+		Error::FailedToReadHeaderByHash {
+			chain: C::NAME.into(),
+			hash: format!("{hash}"),
+			error: e.boxed(),
+		}
+	}
+
+	/// Constructs `FailedToReadBestFinalizedHeaderHash` variant.
+	pub fn failed_to_read_best_finalized_header_hash<C: Chain>(e: Error) -> Self {
+		Error::FailedToReadBestFinalizedHeaderHash { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToReadBestHeader` variant.
+	pub fn failed_to_read_best_header<C: Chain>(e: Error) -> Self {
+		Error::FailedToReadBestHeader { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToReadRuntimeVersion` variant.
+	pub fn failed_to_read_runtime_version<C: Chain>(e: Error) -> Self {
+		Error::FailedToReadRuntimeVersion { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToReadStorageValue` variant.
+	pub fn failed_to_read_storage_value<C: Chain>(
+		at: HashOf<C>,
+		key: StorageKey,
+		e: Error,
+	) -> Self {
+		Error::FailedToReadStorageValue {
+			chain: C::NAME.into(),
+			hash: format!("{at}"),
+			key,
+			error: e.boxed(),
+		}
+	}
+
+	/// Constructs `FailedToGetPendingExtrinsics` variant.
+	pub fn failed_to_get_pending_extrinsics<C: Chain>(e: Error) -> Self {
+		Error::FailedToGetPendingExtrinsics { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToSubmitTransaction` variant.
+	pub fn failed_to_submit_transaction<C: Chain>(e: Error) -> Self {
+		Error::FailedToSubmitTransaction { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedStateCall` variant.
+	pub fn failed_state_call<C: Chain>(
+		at: HashOf<C>,
+		method: String,
+		arguments: Bytes,
+		e: Error,
+	) -> Self {
+		Error::FailedStateCall {
+			chain: C::NAME.into(),
+			hash: format!("{at}"),
+			method,
+			arguments,
+			error: e.boxed(),
+		}
+	}
+
+	/// Constructs `FailedToProveStorage` variant.
+	pub fn failed_to_prove_storage<C: Chain>(
+		at: HashOf<C>,
+		storage_keys: Vec<StorageKey>,
+		e: Error,
+	) -> Self {
+		Error::FailedToProveStorage {
+			chain: C::NAME.into(),
+			hash: format!("{at}"),
+			storage_keys,
+			error: e.boxed(),
+		}
+	}
+
+	/// Constructs `FailedToGetSystemHealth` variant.
+	pub fn failed_to_get_system_health<C: Chain>(e: Error) -> Self {
+		Error::FailedToGetSystemHealth { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToSubscribeBestHeaders` variant.
+	pub fn failed_to_subscribe_best_headers<C: Chain>(e: Error) -> Self {
+		Error::FailedToSubscribeBestHeaders { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToSubscribeFinalizedHeaders` variant.
+	pub fn failed_to_subscribe_finalized_headers<C: Chain>(e: Error) -> Self {
+		Error::FailedToSubscribeFinalizedHeaders { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `FailedToSubscribeJustifications` variant.
+	pub fn failed_to_subscribe_justification<C: Chain>(e: Error) -> Self {
+		Error::FailedToSubscribeJustifications { chain: C::NAME.into(), error: e.boxed() }
+	}
+
+	/// Constructs `Un`
+	pub fn unordered_finalized_headers<C: Chain>(
+		prev_number: BlockNumberOf<C>,
+		next_number: BlockNumberOf<C>,
+	) -> Self {
+		Error::UnorderedFinalizedHeaders {
+			chain: C::NAME.into(),
+			prev_number: format!("{}", prev_number),
+			next_number: format!("{}", next_number),
+		}
+	}
+}
+
+impl MaybeConnectionError for Error {
+	fn is_connection_error(&self) -> bool {
+		match *self {
+			Error::ChannelError(_) => true,
+			Error::RpcError(ref e) => {
+				matches!(*e, RpcError::Transport(_) | RpcError::RestartNeeded(_),)
+			},
+			Error::ClientNotSynced(_) => true,
+			Error::UnorderedFinalizedHeaders { .. } => true,
+			_ => self.nested().map(|e| e.is_connection_error()).unwrap_or(false),
+		}
+	}
+}

pezbridges/relays/client-bizinikiwi/src/guard.rs

@@ -0,0 +1,196 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Pezpallet provides a set of guard functions that are running in background threads
+//! and are aborting process if some condition fails.
+
+use crate::{error::Error, Chain, Client};
+
+use async_trait::async_trait;
+use pezsp_version::RuntimeVersion;
+use std::{
+	fmt::Display,
+	time::{Duration, Instant},
+};
+
+/// Guards environment.
+#[async_trait]
+pub trait Environment<C>: Send + Sync + 'static {
+	/// Error type.
+	type Error: Display + Send + Sync + 'static;
+
+	/// Return current runtime version.
+	async fn runtime_version(&mut self) -> Result<RuntimeVersion, Self::Error>;
+
+	/// Return current time.
+	fn now(&self) -> Instant {
+		Instant::now()
+	}
+
+	/// Sleep given amount of time.
+	async fn sleep(&mut self, duration: Duration) {
+		async_std::task::sleep(duration).await
+	}
+
+	/// Abort current process. Called when guard condition check fails.
+	async fn abort(&mut self) {
+		std::process::abort();
+	}
+}
+
+/// Abort when runtime spec version is different from specified.
+pub fn abort_on_spec_version_change<C: Chain>(
+	mut env: impl Environment<C>,
+	expected_spec_version: u32,
+) {
+	async_std::task::spawn(async move {
+		tracing::info!(
+			target: "bridge-guard",
+			node=%C::NAME,
+			%expected_spec_version,
+			"Starting spec_version guard."
+		);
+
+		loop {
+			let actual_spec_version = env.runtime_version().await;
+			match actual_spec_version {
+				Ok(version) if version.spec_version == expected_spec_version => (),
+				Ok(version) => {
+					tracing::error!(
+						target: "bridge-guard",
+						node=%C::NAME,
+						from=%expected_spec_version,
+						to=%version.spec_version,
+						"Runtime spec version has changed. Aborting relay"
+					);
+
+					env.abort().await;
+				},
+				Err(error) => tracing::warn!(
+					target: "bridge-guard",
+					%error,
+					node=%C::NAME,
+					"Failed to read runtime version. Relay may need to be stopped manually"
+				),
+			}
+
+			env.sleep(conditions_check_delay::<C>()).await;
+		}
+	});
+}
+
+/// Delay between conditions check.
+fn conditions_check_delay<C: Chain>() -> Duration {
+	C::AVERAGE_BLOCK_INTERVAL * (10 + rand::random::<u32>() % 10)
+}
+
+#[async_trait]
+impl<C: Chain, Clnt: Client<C>> Environment<C> for Clnt {
+	type Error = Error;
+
+	async fn runtime_version(&mut self) -> Result<RuntimeVersion, Self::Error> {
+		Client::<C>::runtime_version(self).await
+	}
+}
+
+#[cfg(test)]
+pub(crate) mod tests {
+	use super::*;
+	use crate::test_chain::TestChain;
+	use futures::{
+		channel::mpsc::{unbounded, UnboundedReceiver, UnboundedSender},
+		future::FutureExt,
+		stream::StreamExt,
+		SinkExt,
+	};
+
+	pub struct TestEnvironment {
+		pub runtime_version_rx: UnboundedReceiver<RuntimeVersion>,
+		pub slept_tx: UnboundedSender<()>,
+		pub aborted_tx: UnboundedSender<()>,
+	}
+
+	#[async_trait]
+	impl Environment<TestChain> for TestEnvironment {
+		type Error = Error;
+
+		async fn runtime_version(&mut self) -> Result<RuntimeVersion, Self::Error> {
+			Ok(self.runtime_version_rx.next().await.unwrap_or_default())
+		}
+
+		async fn sleep(&mut self, _duration: Duration) {
+			let _ = self.slept_tx.send(()).await;
+		}
+
+		async fn abort(&mut self) {
+			let _ = self.aborted_tx.send(()).await;
+			// simulate process abort :)
+			async_std::task::sleep(Duration::from_secs(60)).await;
+		}
+	}
+
+	#[test]
+	fn aborts_when_spec_version_is_changed() {
+		async_std::task::block_on(async {
+			let (
+				(mut runtime_version_tx, runtime_version_rx),
+				(slept_tx, mut slept_rx),
+				(aborted_tx, mut aborted_rx),
+			) = (unbounded(), unbounded(), unbounded());
+			abort_on_spec_version_change(
+				TestEnvironment { runtime_version_rx, slept_tx, aborted_tx },
+				0,
+			);
+
+			// client responds with wrong version
+			runtime_version_tx
+				.send(RuntimeVersion { spec_version: 42, ..Default::default() })
+				.await
+				.unwrap();
+
+			// then the `abort` function is called
+			aborted_rx.next().await;
+			// and we do not reach the `sleep` function call
+			assert!(slept_rx.next().now_or_never().is_none());
+		});
+	}
+
+	#[test]
+	fn does_not_aborts_when_spec_version_is_unchanged() {
+		async_std::task::block_on(async {
+			let (
+				(mut runtime_version_tx, runtime_version_rx),
+				(slept_tx, mut slept_rx),
+				(aborted_tx, mut aborted_rx),
+			) = (unbounded(), unbounded(), unbounded());
+			abort_on_spec_version_change(
+				TestEnvironment { runtime_version_rx, slept_tx, aborted_tx },
+				42,
+			);
+
+			// client responds with the same version
+			runtime_version_tx
+				.send(RuntimeVersion { spec_version: 42, ..Default::default() })
+				.await
+				.unwrap();
+
+			// then the `sleep` function is called
+			slept_rx.next().await;
+			// and the `abort` function is not called
+			assert!(aborted_rx.next().now_or_never().is_none());
+		});
+	}
+}

pezbridges/relays/client-bizinikiwi/src/lib.rs

@@ -0,0 +1,88 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Tools to interact with Bizinikiwi node using RPC methods.
+
+#![warn(missing_docs)]
+
+mod chain;
+mod client;
+mod error;
+mod sync_header;
+mod transaction_tracker;
+
+pub mod calls;
+pub mod guard;
+pub mod metrics;
+pub mod test_chain;
+
+use std::time::Duration;
+
+pub use crate::{
+	chain::{
+		AccountKeyPairOf, BlockWithJustification, CallOf, Chain, ChainWithBalances,
+		ChainWithGrandpa, ChainWithMessages, ChainWithRewards, ChainWithRuntimeVersion,
+		ChainWithTransactions, ChainWithUtilityPallet, FullRuntimeUtilityPallet,
+		MockedRuntimeUtilityPallet, RelayChain, SignParam, SignedBlockOf, Teyrchain,
+		TransactionStatusOf, UnsignedTransaction, UtilityPallet,
+	},
+	client::{
+		is_ancient_block, rpc_with_caching as new, ChainRuntimeVersion, Client,
+		OpaqueGrandpaAuthoritiesSet, RpcWithCachingClient, SimpleRuntimeVersion, StreamDescription,
+		Subscription, ANCIENT_BLOCK_THRESHOLD,
+	},
+	error::{Error, Result},
+	sync_header::SyncHeader,
+	transaction_tracker::TransactionTracker,
+};
+pub use pezbp_runtime::{
+	AccountIdOf, AccountPublicOf, BalanceOf, BlockNumberOf, Chain as ChainBase, HashOf, HeaderIdOf,
+	HeaderOf, NonceOf, SignatureOf, Teyrchain as TeyrchainBase, TransactionEra, TransactionEraOf,
+	UnderlyingChainProvider,
+};
+
+/// Bizinikiwi-over-websocket connection params.
+#[derive(Debug, Clone)]
+pub struct ConnectionParams {
+	/// Websocket endpoint URL.
+	pub uri: String,
+	/// Defined chain runtime version
+	pub chain_runtime_version: ChainRuntimeVersion,
+}
+
+impl Default for ConnectionParams {
+	fn default() -> Self {
+		ConnectionParams {
+			uri: "ws://localhost:9944".into(),
+			chain_runtime_version: ChainRuntimeVersion::Auto,
+		}
+	}
+}
+
+/// Returns stall timeout for relay loop.
+///
+/// Relay considers himself stalled if he has submitted transaction to the node, but it has not
+/// been mined for this period.
+pub fn transaction_stall_timeout(
+	mortality_period: Option<u32>,
+	average_block_interval: Duration,
+	default_stall_timeout: Duration,
+) -> Duration {
+	// 1 extra block for transaction to reach the pool && 1 for relayer to awake after it is mined
+	mortality_period
+		.map(|mortality_period| average_block_interval.saturating_mul(mortality_period + 1 + 1))
+		.unwrap_or(default_stall_timeout)
+}

pezbridges/relays/client-bizinikiwi/src/metrics/float_storage_value.rs

@@ -0,0 +1,140 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::{Chain, Client, Error as BizinikiwiError};
+
+use async_std::sync::{Arc, RwLock};
+use async_trait::async_trait;
+use codec::Decode;
+use num_traits::One;
+use relay_utils::metrics::{
+	metric_name, register, F64SharedRef, Gauge, Metric, PrometheusError, Registry,
+	StandaloneMetric, F64,
+};
+use pezsp_core::storage::{StorageData, StorageKey};
+use pezsp_runtime::{traits::UniqueSaturatedInto, FixedPointNumber, FixedU128};
+use std::{marker::PhantomData, time::Duration};
+
+/// Storage value update interval (in blocks).
+const UPDATE_INTERVAL_IN_BLOCKS: u32 = 5;
+
+/// Fied-point storage value and the way it is decoded from the raw storage value.
+pub trait FloatStorageValue: 'static + Clone + Send + Sync {
+	/// Type of the value.
+	type Value: FixedPointNumber;
+	/// Try to decode value from the raw storage value.
+	fn decode(
+		&self,
+		maybe_raw_value: Option<StorageData>,
+	) -> Result<Option<Self::Value>, BizinikiwiError>;
+}
+
+/// Implementation of `FloatStorageValue` that expects encoded `FixedU128` value and returns `1` if
+/// value is missing from the storage.
+#[derive(Clone, Debug, Default)]
+pub struct FixedU128OrOne;
+
+impl FloatStorageValue for FixedU128OrOne {
+	type Value = FixedU128;
+
+	fn decode(
+		&self,
+		maybe_raw_value: Option<StorageData>,
+	) -> Result<Option<Self::Value>, BizinikiwiError> {
+		maybe_raw_value
+			.map(|raw_value| {
+				FixedU128::decode(&mut &raw_value.0[..])
+					.map_err(BizinikiwiError::ResponseParseFailed)
+					.map(Some)
+			})
+			.unwrap_or_else(|| Ok(Some(FixedU128::one())))
+	}
+}
+
+/// Metric that represents fixed-point runtime storage value as float gauge.
+#[derive(Clone, Debug)]
+pub struct FloatStorageValueMetric<C, Clnt, V> {
+	value_converter: V,
+	client: Clnt,
+	storage_key: StorageKey,
+	metric: Gauge<F64>,
+	shared_value_ref: F64SharedRef,
+	_phantom: PhantomData<(C, V)>,
+}
+
+impl<C, Clnt, V> FloatStorageValueMetric<C, Clnt, V> {
+	/// Create new metric.
+	pub fn new(
+		value_converter: V,
+		client: Clnt,
+		storage_key: StorageKey,
+		name: String,
+		help: String,
+	) -> Result<Self, PrometheusError> {
+		let shared_value_ref = Arc::new(RwLock::new(None));
+		Ok(FloatStorageValueMetric {
+			value_converter,
+			client,
+			storage_key,
+			metric: Gauge::new(metric_name(None, &name), help)?,
+			shared_value_ref,
+			_phantom: Default::default(),
+		})
+	}
+
+	/// Get shared reference to metric value.
+	pub fn shared_value_ref(&self) -> F64SharedRef {
+		self.shared_value_ref.clone()
+	}
+}
+
+impl<C: Chain, Clnt: Client<C>, V: FloatStorageValue> Metric
+	for FloatStorageValueMetric<C, Clnt, V>
+{
+	fn register(&self, registry: &Registry) -> Result<(), PrometheusError> {
+		register(self.metric.clone(), registry).map(drop)
+	}
+}
+
+#[async_trait]
+impl<C: Chain, Clnt: Client<C>, V: FloatStorageValue> StandaloneMetric
+	for FloatStorageValueMetric<C, Clnt, V>
+{
+	fn update_interval(&self) -> Duration {
+		C::AVERAGE_BLOCK_INTERVAL * UPDATE_INTERVAL_IN_BLOCKS
+	}
+
+	async fn update(&self) {
+		let value = async move {
+			let best_header_hash = self.client.best_header_hash().await?;
+			let maybe_storage_value = self
+				.client
+				.raw_storage_value(best_header_hash, self.storage_key.clone())
+				.await?;
+			self.value_converter.decode(maybe_storage_value).map(|maybe_fixed_point_value| {
+				maybe_fixed_point_value.map(|fixed_point_value| {
+					fixed_point_value.into_inner().unique_saturated_into() as f64 /
+						V::Value::DIV.unique_saturated_into() as f64
+				})
+			})
+		}
+		.await
+		.map_err(|e| e.to_string());
+
+		relay_utils::metrics::set_gauge_value(&self.metric, value.clone());
+		*self.shared_value_ref.write().await = value.ok().and_then(|x| x);
+	}
+}

pezbridges/relays/client-bizinikiwi/src/metrics/mod.rs

@@ -0,0 +1,21 @@
+// Copyright 2019-2020 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Contains several Bizinikiwi-specific metrics that may be exposed by relay.
+
+pub use float_storage_value::{FixedU128OrOne, FloatStorageValue, FloatStorageValueMetric};
+
+mod float_storage_value;

pezbridges/relays/client-bizinikiwi/src/sync_header.rs

@@ -0,0 +1,61 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+use bp_header_pez_chain::ConsensusLogReader;
+use pez_finality_relay::SourceHeader as FinalitySourceHeader;
+use pezsp_runtime::traits::Header as HeaderT;
+
+/// Generic wrapper for `pezsp_runtime::traits::Header` based headers, that
+/// implements `pez_finality_relay::SourceHeader` and may be used in headers sync directly.
+#[derive(Clone, Debug, PartialEq)]
+pub struct SyncHeader<Header>(Header);
+
+impl<Header> SyncHeader<Header> {
+	/// Extracts wrapped header from self.
+	pub fn into_inner(self) -> Header {
+		self.0
+	}
+}
+
+impl<Header> std::ops::Deref for SyncHeader<Header> {
+	type Target = Header;
+
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
+
+impl<Header> From<Header> for SyncHeader<Header> {
+	fn from(header: Header) -> Self {
+		Self(header)
+	}
+}
+
+impl<Header: HeaderT, R: ConsensusLogReader> FinalitySourceHeader<Header::Hash, Header::Number, R>
+	for SyncHeader<Header>
+{
+	fn hash(&self) -> Header::Hash {
+		self.0.hash()
+	}
+
+	fn number(&self) -> Header::Number {
+		*self.0.number()
+	}
+
+	fn is_mandatory(&self) -> bool {
+		R::schedules_authorities_change(self.digest())
+	}
+}

pezbridges/relays/client-bizinikiwi/src/test_chain.rs

@@ -0,0 +1,200 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Pezpallet provides a set of guard functions that are running in background threads
+//! and are aborting process if some condition fails.
+
+//! Test chain implementation to use in tests.
+
+#![cfg(any(feature = "test-helpers", test))]
+
+use crate::{
+	Chain, ChainWithBalances, ChainWithMessages, ChainWithRewards, ChainWithTransactions,
+	Error as BizinikiwiError, SignParam, UnsignedTransaction,
+};
+use bp_messages::{ChainWithMessages as ChainWithMessagesBase, MessageNonce};
+use pezbp_runtime::ChainId;
+use codec::{Decode, DecodeWithMemTracking, Encode, MaxEncodedLen};
+use pezframe_support::{pezsp_runtime::StateVersion, weights::Weight};
+use scale_info::TypeInfo;
+use std::time::Duration;
+
+/// Chain that may be used in tests.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TestChain;
+
+impl pezbp_runtime::Chain for TestChain {
+	const ID: ChainId = *b"test";
+
+	type BlockNumber = u32;
+	type Hash = pezsp_core::H256;
+	type Hasher = pezsp_runtime::traits::BlakeTwo256;
+	type Header = pezsp_runtime::generic::Header<u32, pezsp_runtime::traits::BlakeTwo256>;
+
+	type AccountId = u32;
+	type Balance = u32;
+	type Nonce = u32;
+	type Signature = pezsp_runtime::testing::TestSignature;
+
+	const STATE_VERSION: StateVersion = StateVersion::V1;
+
+	fn max_extrinsic_size() -> u32 {
+		100000
+	}
+
+	fn max_extrinsic_weight() -> Weight {
+		unreachable!()
+	}
+}
+
+impl Chain for TestChain {
+	const NAME: &'static str = "Test";
+	const BEST_FINALIZED_HEADER_ID_METHOD: &'static str = "TestMethod";
+	const FREE_HEADERS_INTERVAL_METHOD: &'static str = "TestMethod";
+	const AVERAGE_BLOCK_INTERVAL: Duration = Duration::from_millis(0);
+
+	type SignedBlock = pezsp_runtime::generic::SignedBlock<
+		pezsp_runtime::generic::Block<Self::Header, pezsp_runtime::OpaqueExtrinsic>,
+	>;
+	type Call = TestRuntimeCall;
+}
+
+impl ChainWithBalances for TestChain {
+	fn account_info_storage_key(_account_id: &u32) -> pezsp_core::storage::StorageKey {
+		unreachable!()
+	}
+}
+
+/// Reward type for the test chain.
+#[derive(
+	Clone,
+	Copy,
+	Debug,
+	Decode,
+	DecodeWithMemTracking,
+	Encode,
+	Eq,
+	MaxEncodedLen,
+	PartialEq,
+	TypeInfo,
+)]
+pub enum ChainReward {
+	/// Reward 1 type.
+	Reward1,
+}
+
+impl ChainWithRewards for TestChain {
+	const WITH_CHAIN_RELAYERS_PALLET_NAME: Option<&'static str> = None;
+	type RewardBalance = u128;
+	type Reward = ChainReward;
+
+	fn account_reward_storage_key(
+		_account_id: &Self::AccountId,
+		_reward: impl Into<Self::Reward>,
+	) -> pezsp_core::storage::StorageKey {
+		unreachable!()
+	}
+}
+
+impl ChainWithMessagesBase for TestChain {
+	const WITH_CHAIN_MESSAGES_PALLET_NAME: &'static str = "Test";
+	const MAX_UNREWARDED_RELAYERS_IN_CONFIRMATION_TX: MessageNonce = 0;
+	const MAX_UNCONFIRMED_MESSAGES_IN_CONFIRMATION_TX: MessageNonce = 0;
+}
+
+impl ChainWithMessages for TestChain {
+	const TO_CHAIN_MESSAGE_DETAILS_METHOD: &'static str = "TestMessagesDetailsMethod";
+	const FROM_CHAIN_MESSAGE_DETAILS_METHOD: &'static str = "TestFromMessagesDetailsMethod";
+}
+
+impl ChainWithTransactions for TestChain {
+	type AccountKeyPair = pezsp_core::sr25519::Pair;
+	type SignedTransaction = bp_pezkuwi_core::UncheckedExtrinsic<
+		TestRuntimeCall,
+		bp_pezkuwi_core::SuffixedCommonTransactionExtension<(
+			pezbp_runtime::extensions::BridgeRejectObsoleteHeadersAndMessages,
+			pezbp_runtime::extensions::RefundBridgedTeyrchainMessagesSchema,
+		)>,
+	>;
+
+	fn sign_transaction(
+		_param: SignParam<Self>,
+		_unsigned: UnsignedTransaction<Self>,
+	) -> Result<Self::SignedTransaction, BizinikiwiError> {
+		unreachable!()
+	}
+}
+
+/// Dummy runtime call.
+#[derive(Decode, Encode, Clone, Debug, PartialEq)]
+pub enum TestRuntimeCall {
+	/// Dummy call.
+	#[codec(index = 0)]
+	Dummy,
+}
+
+/// Primitives-level teyrchain that may be used in tests.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TestTeyrchainBase;
+
+impl pezbp_runtime::Chain for TestTeyrchainBase {
+	const ID: ChainId = *b"tstp";
+
+	type BlockNumber = u32;
+	type Hash = pezsp_core::H256;
+	type Hasher = pezsp_runtime::traits::BlakeTwo256;
+	type Header = pezsp_runtime::generic::Header<u32, pezsp_runtime::traits::BlakeTwo256>;
+
+	type AccountId = u32;
+	type Balance = u32;
+	type Nonce = u32;
+	type Signature = pezsp_runtime::testing::TestSignature;
+
+	const STATE_VERSION: StateVersion = StateVersion::V1;
+
+	fn max_extrinsic_size() -> u32 {
+		unreachable!()
+	}
+
+	fn max_extrinsic_weight() -> Weight {
+		unreachable!()
+	}
+}
+
+impl pezbp_runtime::Teyrchain for TestTeyrchainBase {
+	const TEYRCHAIN_ID: u32 = 1000;
+	const MAX_HEADER_SIZE: u32 = 1_024;
+}
+
+/// Teyrchain that may be used in tests.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TestTeyrchain;
+
+impl pezbp_runtime::UnderlyingChainProvider for TestTeyrchain {
+	type Chain = TestTeyrchainBase;
+}
+
+impl Chain for TestTeyrchain {
+	const NAME: &'static str = "TestTeyrchain";
+	const BEST_FINALIZED_HEADER_ID_METHOD: &'static str = "TestTeyrchainMethod";
+	const FREE_HEADERS_INTERVAL_METHOD: &'static str = "TestTeyrchainMethod";
+	const AVERAGE_BLOCK_INTERVAL: Duration = Duration::from_millis(0);
+
+	type SignedBlock = pezsp_runtime::generic::SignedBlock<
+		pezsp_runtime::generic::Block<Self::Header, pezsp_runtime::OpaqueExtrinsic>,
+	>;
+	type Call = TestRuntimeCall;
+}

pezbridges/relays/client-bizinikiwi/src/transaction_tracker.rs

@@ -0,0 +1,473 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Helper for tracking transaction invalidation events.
+
+use crate::{Chain, Error, HashOf, HeaderIdOf, Subscription, TransactionStatusOf};
+
+use async_trait::async_trait;
+use futures::{future::Either, Future, FutureExt, Stream, StreamExt};
+use relay_utils::{HeaderId, TrackedTransactionStatus};
+use pezsp_runtime::traits::Header as _;
+use std::time::Duration;
+
+/// Transaction tracker environment.
+#[async_trait]
+pub trait Environment<C: Chain>: Send + Sync {
+	/// Returns header id by its hash.
+	async fn header_id_by_hash(&self, hash: HashOf<C>) -> Result<HeaderIdOf<C>, Error>;
+}
+
+// TODO (https://github.com/pezkuwichain/kurdistan-sdk/issues/84): remove `Environment` trait
+// after test client is implemented
+#[async_trait]
+impl<C: Chain, T: crate::client::Client<C>> Environment<C> for T {
+	async fn header_id_by_hash(&self, hash: HashOf<C>) -> Result<HeaderIdOf<C>, Error> {
+		self.header_by_hash(hash).await.map(|h| HeaderId(*h.number(), hash))
+	}
+}
+
+/// Bizinikiwi transaction tracker implementation.
+///
+/// Bizinikiwi node provides RPC API to submit and watch for transaction events. This way
+/// we may know when transaction is included into block, finalized or rejected. There are
+/// some edge cases, when we can't fully trust this mechanism - e.g. transaction may broadcasted
+/// and then dropped out of node transaction pool (some other cases are also possible - node
+/// restarts, connection lost, ...). Then we can't know for sure - what is currently happening
+/// with our transaction. Is the transaction really lost? Is it still alive on the chain network?
+///
+/// We have several options to handle such cases:
+///
+/// 1) hope that the transaction is still alive and wait for its mining until it is spoiled;
+///
+/// 2) assume that the transaction is lost and resubmit another transaction instantly;
+///
+/// 3) wait for some time (if transaction is mortal - then until block where it dies; if it is
+///    immortal - then for some time that we assume is long enough to mine it) and assume that it is
+///    lost.
+///
+/// This struct implements third option as it seems to be the most optimal.
+pub struct TransactionTracker<C: Chain, E> {
+	environment: E,
+	transaction_hash: HashOf<C>,
+	stall_timeout: Duration,
+	subscription: Subscription<TransactionStatusOf<C>>,
+}
+
+impl<C: Chain, E: Environment<C>> TransactionTracker<C, E> {
+	/// Create transaction tracker.
+	pub fn new(
+		environment: E,
+		stall_timeout: Duration,
+		transaction_hash: HashOf<C>,
+		subscription: Subscription<TransactionStatusOf<C>>,
+	) -> Self {
+		Self { environment, stall_timeout, transaction_hash, subscription }
+	}
+
+	// TODO (https://github.com/pezkuwichain/kurdistan-sdk/issues/84): remove me after
+	// test client is implemented
+	/// Converts self into tracker with different environment.
+	pub fn switch_environment<NewE: Environment<C>>(
+		self,
+		environment: NewE,
+	) -> TransactionTracker<C, NewE> {
+		TransactionTracker {
+			environment,
+			stall_timeout: self.stall_timeout,
+			transaction_hash: self.transaction_hash,
+			subscription: self.subscription,
+		}
+	}
+
+	/// Wait for final transaction status and return it along with last known internal invalidation
+	/// status.
+	async fn do_wait(
+		self,
+		wait_for_stall_timeout: impl Future<Output = ()>,
+		wait_for_stall_timeout_rest: impl Future<Output = ()>,
+	) -> (TrackedTransactionStatus<HeaderIdOf<C>>, Option<InvalidationStatus<HeaderIdOf<C>>>) {
+		// sometimes we want to wait for the rest of the stall timeout even if
+		// `wait_for_invalidation` has been "select"ed first => it is shared
+		let wait_for_invalidation = watch_transaction_status::<_, C, _>(
+			self.environment,
+			self.transaction_hash,
+			self.subscription,
+		);
+		futures::pin_mut!(wait_for_stall_timeout, wait_for_invalidation);
+
+		match futures::future::select(wait_for_stall_timeout, wait_for_invalidation).await {
+			Either::Left((_, _)) => {
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?self.transaction_hash,
+					"Transaction is considered lost after timeout (no status response from the node)"
+				);
+
+				(TrackedTransactionStatus::Lost, None)
+			},
+			Either::Right((invalidation_status, _)) => match invalidation_status {
+				InvalidationStatus::Finalized(at_block) =>
+					(TrackedTransactionStatus::Finalized(at_block), Some(invalidation_status)),
+				InvalidationStatus::Invalid =>
+					(TrackedTransactionStatus::Lost, Some(invalidation_status)),
+				InvalidationStatus::Lost => {
+					// wait for the rest of stall timeout - this way we'll be sure that the
+					// transaction is actually dead if it has been crafted properly
+					wait_for_stall_timeout_rest.await;
+					// if someone is still watching for our transaction, then we're reporting
+					// an error here (which is treated as "transaction lost")
+					tracing::trace!(
+						target: "bridge",
+						node=%C::NAME,
+						transaction=?self.transaction_hash,
+						"Transaction is considered lost after timeout"
+					);
+
+					(TrackedTransactionStatus::Lost, Some(invalidation_status))
+				},
+			},
+		}
+	}
+}
+
+#[async_trait]
+impl<C: Chain, E: Environment<C>> relay_utils::TransactionTracker for TransactionTracker<C, E> {
+	type HeaderId = HeaderIdOf<C>;
+
+	async fn wait(self) -> TrackedTransactionStatus<HeaderIdOf<C>> {
+		let wait_for_stall_timeout = async_std::task::sleep(self.stall_timeout).shared();
+		let wait_for_stall_timeout_rest = wait_for_stall_timeout.clone();
+		self.do_wait(wait_for_stall_timeout, wait_for_stall_timeout_rest).await.0
+	}
+}
+
+/// Transaction invalidation status.
+///
+/// Note that in places where the `TransactionTracker` is used, the finalization event will be
+/// ignored - relay loops are detecting the mining/finalization using their own
+/// techniques. That's why we're using `InvalidationStatus` here.
+#[derive(Debug, PartialEq)]
+enum InvalidationStatus<BlockId> {
+	/// Transaction has been included into block and finalized at given block.
+	Finalized(BlockId),
+	/// Transaction has been invalidated.
+	Invalid,
+	/// We have lost track of transaction status.
+	Lost,
+}
+
+/// Watch for transaction status until transaction is finalized or we lose track of its status.
+async fn watch_transaction_status<
+	E: Environment<C>,
+	C: Chain,
+	S: Stream<Item = TransactionStatusOf<C>>,
+>(
+	environment: E,
+	transaction_hash: HashOf<C>,
+	subscription: S,
+) -> InvalidationStatus<HeaderIdOf<C>> {
+	futures::pin_mut!(subscription);
+
+	loop {
+		match subscription.next().await {
+			Some(TransactionStatusOf::<C>::Finalized((block_hash, _))) => {
+				// the only "successful" outcome of this method is when the block with transaction
+				// has been finalized
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					block=?block_hash,
+					"Transaction has been finalized"
+				);
+
+				let header_id = match environment.header_id_by_hash(block_hash).await {
+					Ok(header_id) => header_id,
+					Err(e) => {
+						tracing::error!(
+							target: "bridge",
+							error=?e,
+							node=%C::NAME,
+							transaction=?transaction_hash,
+							block=?block_hash,
+							"Failed to read header when watching for transaction",
+						);
+						// that's the best option we have here
+						return InvalidationStatus::Lost;
+					},
+				};
+				return InvalidationStatus::Finalized(header_id);
+			},
+			Some(TransactionStatusOf::<C>::Invalid) => {
+				// if node says that the transaction is invalid, there are still chances that
+				// it is not actually invalid - e.g. if the block where transaction has been
+				// revalidated is retracted and transaction (at some other node pool) becomes
+				// valid again on other fork. But let's assume that the chances of this event
+				// are almost zero - there's a lot of things that must happen for this to be the
+				// case.
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					"Transaction has been invalidated"
+				);
+				return InvalidationStatus::Invalid;
+			},
+			Some(TransactionStatusOf::<C>::Future) |
+			Some(TransactionStatusOf::<C>::Ready) |
+			Some(TransactionStatusOf::<C>::Broadcast(_)) => {
+				// nothing important (for us) has happened
+			},
+			Some(TransactionStatusOf::<C>::InBlock(block_hash)) => {
+				// TODO: read matching system event (ExtrinsicSuccess or ExtrinsicFailed), log it
+				// here and use it later (on finality) for reporting invalid transaction
+				// https://github.com/pezkuwichain/kurdistan-sdk/issues/79
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					block=?block_hash,
+					"Transaction has been included"
+				);
+			},
+			Some(TransactionStatusOf::<C>::Retracted(block_hash)) => {
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					block=?block_hash,
+					"Transaction has been retracted"
+				);
+			},
+			Some(TransactionStatusOf::<C>::FinalityTimeout(block_hash)) => {
+				// finality is lagging? let's wait a bit more and report a stall
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					block=?block_hash,
+					"Transaction has not been finalized for too long"
+				);
+				return InvalidationStatus::Lost;
+			},
+			Some(TransactionStatusOf::<C>::Usurped(new_transaction_hash)) => {
+				// this may be result of our transaction resubmitter work or some manual
+				// intervention. In both cases - let's start stall timeout, because the meaning
+				// of transaction may have changed
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					new_transaction=?new_transaction_hash,
+					"Transaction has been usurped"
+				);
+				return InvalidationStatus::Lost;
+			},
+			Some(TransactionStatusOf::<C>::Dropped) => {
+				// the transaction has been removed from the pool because of its limits. Let's wait
+				// a bit and report a stall
+				tracing::trace!(
+					target: "bridge",
+					node=%C::NAME,
+					transaction=?transaction_hash,
+					"Transaction has been dropped from the pool"
+				);
+				return InvalidationStatus::Lost;
+			},
+			None => {
+				// the status of transaction is unknown to us (the subscription has been closed?).
+				// Let's wait a bit and report a stall
+				return InvalidationStatus::Lost;
+			},
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::{test_chain::TestChain, StreamDescription};
+	use futures::{FutureExt, SinkExt};
+	use pezsc_transaction_pool_api::TransactionStatus;
+
+	struct TestEnvironment(Result<HeaderIdOf<TestChain>, Error>);
+
+	#[async_trait]
+	impl Environment<TestChain> for TestEnvironment {
+		async fn header_id_by_hash(
+			&self,
+			_hash: HashOf<TestChain>,
+		) -> Result<HeaderIdOf<TestChain>, Error> {
+			self.0.as_ref().map_err(|_| Error::BridgePalletIsNotInitialized).cloned()
+		}
+	}
+
+	async fn on_transaction_status(
+		status: TransactionStatus<HashOf<TestChain>, HashOf<TestChain>>,
+	) -> Option<(
+		TrackedTransactionStatus<HeaderIdOf<TestChain>>,
+		InvalidationStatus<HeaderIdOf<TestChain>>,
+	)> {
+		let (mut sender, receiver) = futures::channel::mpsc::channel(1);
+		let tx_tracker = TransactionTracker::<TestChain, TestEnvironment>::new(
+			TestEnvironment(Ok(HeaderId(0, Default::default()))),
+			Duration::from_secs(0),
+			Default::default(),
+			Subscription::new_forwarded(
+				StreamDescription::new("test".into(), "test".into()),
+				receiver,
+			),
+		);
+
+		// we can't do `.now_or_never()` on `do_wait()` call, because `Subscription` has its own
+		// background thread, which may cause additional async task switches => let's leave some
+		// relatively small timeout here
+		let wait_for_stall_timeout = async_std::task::sleep(std::time::Duration::from_millis(100));
+		let wait_for_stall_timeout_rest = futures::future::ready(());
+		sender.send(Ok(status)).await.unwrap();
+
+		let (ts, is) =
+			tx_tracker.do_wait(wait_for_stall_timeout, wait_for_stall_timeout_rest).await;
+		is.map(|is| (ts, is))
+	}
+
+	#[async_std::test]
+	async fn returns_finalized_on_finalized() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::Finalized(Default::default())).await,
+			Some((
+				TrackedTransactionStatus::Finalized(Default::default()),
+				InvalidationStatus::Finalized(Default::default())
+			)),
+		);
+	}
+
+	#[async_std::test]
+	async fn returns_lost_on_finalized_and_environment_error() {
+		assert_eq!(
+			watch_transaction_status::<_, TestChain, _>(
+				TestEnvironment(Err(Error::BridgePalletIsNotInitialized)),
+				Default::default(),
+				futures::stream::iter([TransactionStatus::Finalized(Default::default())])
+			)
+			.now_or_never(),
+			Some(InvalidationStatus::Lost),
+		);
+	}
+
+	#[async_std::test]
+	async fn returns_invalid_on_invalid() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::Invalid).await,
+			Some((TrackedTransactionStatus::Lost, InvalidationStatus::Invalid)),
+		);
+	}
+
+	#[async_std::test]
+	async fn waits_on_future() {
+		assert_eq!(on_transaction_status(TransactionStatus::Future).await, None,);
+	}
+
+	#[async_std::test]
+	async fn waits_on_ready() {
+		assert_eq!(on_transaction_status(TransactionStatus::Ready).await, None,);
+	}
+
+	#[async_std::test]
+	async fn waits_on_broadcast() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::Broadcast(Default::default())).await,
+			None,
+		);
+	}
+
+	#[async_std::test]
+	async fn waits_on_in_block() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::InBlock(Default::default())).await,
+			None,
+		);
+	}
+
+	#[async_std::test]
+	async fn waits_on_retracted() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::Retracted(Default::default())).await,
+			None,
+		);
+	}
+
+	#[async_std::test]
+	async fn lost_on_finality_timeout() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::FinalityTimeout(Default::default())).await,
+			Some((TrackedTransactionStatus::Lost, InvalidationStatus::Lost)),
+		);
+	}
+
+	#[async_std::test]
+	async fn lost_on_usurped() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::Usurped(Default::default())).await,
+			Some((TrackedTransactionStatus::Lost, InvalidationStatus::Lost)),
+		);
+	}
+
+	#[async_std::test]
+	async fn lost_on_dropped() {
+		assert_eq!(
+			on_transaction_status(TransactionStatus::Dropped).await,
+			Some((TrackedTransactionStatus::Lost, InvalidationStatus::Lost)),
+		);
+	}
+
+	#[async_std::test]
+	async fn lost_on_subscription_error() {
+		assert_eq!(
+			watch_transaction_status::<_, TestChain, _>(
+				TestEnvironment(Ok(HeaderId(0, Default::default()))),
+				Default::default(),
+				futures::stream::iter([])
+			)
+			.now_or_never(),
+			Some(InvalidationStatus::Lost),
+		);
+	}
+
+	#[async_std::test]
+	async fn lost_on_timeout_when_waiting_for_invalidation_status() {
+		let (_sender, receiver) = futures::channel::mpsc::channel(1);
+		let tx_tracker = TransactionTracker::<TestChain, TestEnvironment>::new(
+			TestEnvironment(Ok(HeaderId(0, Default::default()))),
+			Duration::from_secs(0),
+			Default::default(),
+			Subscription::new_forwarded(
+				StreamDescription::new("test".into(), "test".into()),
+				receiver,
+			),
+		);
+
+		let wait_for_stall_timeout = futures::future::ready(()).shared();
+		let wait_for_stall_timeout_rest = wait_for_stall_timeout.clone();
+		let wait_result = tx_tracker
+			.do_wait(wait_for_stall_timeout, wait_for_stall_timeout_rest)
+			.now_or_never();
+
+		assert_eq!(wait_result, Some((TrackedTransactionStatus::Lost, None)));
+	}
+}