Merge commit 'e5bed7ac380b6adb54b60a2a72a2a8f07f50d6c1' as 'bridges'

polkadot/bridges/relays/client-substrate/src/chain.rs

@@ -0,0 +1,105 @@
+// 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_runtime::Chain as ChainBase;
+use frame_support::Parameter;
+use jsonrpsee_ws_client::{DeserializeOwned, Serialize};
+use num_traits::{CheckedSub, Zero};
+use sp_core::{storage::StorageKey, Pair};
+use sp_runtime::{
+	generic::SignedBlock,
+	traits::{
+		AtLeast32Bit, Block as BlockT, Dispatchable, MaybeDisplay, MaybeSerialize, MaybeSerializeDeserialize, Member,
+	},
+	EncodedJustification,
+};
+use std::{fmt::Debug, time::Duration};
+
+/// Substrate-based chain from minimal relay-client point of view.
+pub trait Chain: ChainBase + Clone {
+	/// Chain name.
+	const NAME: &'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;
+
+	/// The user account identifier type for the runtime.
+	type AccountId: Parameter + Member + MaybeSerializeDeserialize + Debug + MaybeDisplay + Ord + Default;
+	/// Index of a transaction used by the chain.
+	type Index: Parameter
+		+ Member
+		+ MaybeSerialize
+		+ Debug
+		+ Default
+		+ MaybeDisplay
+		+ DeserializeOwned
+		+ AtLeast32Bit
+		+ Copy;
+	/// Block type.
+	type SignedBlock: Member + Serialize + DeserializeOwned + BlockWithJustification<Self::Header>;
+	/// The aggregated `Call` type.
+	type Call: Dispatchable + Debug;
+}
+
+/// Substrate-based chain with `frame_system::Config::AccountData` set to
+/// the `pallet_balances::AccountData<NativeBalance>`.
+pub trait ChainWithBalances: Chain {
+	/// Balance of an account in native tokens.
+	type NativeBalance: Parameter + Member + DeserializeOwned + Clone + Copy + CheckedSub + PartialOrd + Zero;
+
+	/// Return runtime storage key for getting `frame_system::AccountInfo` of given account.
+	fn account_info_storage_key(account_id: &Self::AccountId) -> StorageKey;
+}
+
+/// Block with justification.
+pub trait BlockWithJustification<Header> {
+	/// Return block header.
+	fn header(&self) -> Header;
+	/// Return block justification, if known.
+	fn justification(&self) -> Option<&EncodedJustification>;
+}
+
+/// Substrate-based chain transactions signing scheme.
+pub trait TransactionSignScheme {
+	/// Chain that this scheme is to be used.
+	type Chain: Chain;
+	/// Type of key pairs used to sign transactions.
+	type AccountKeyPair: Pair;
+	/// Signed transaction.
+	type SignedTransaction;
+
+	/// Create transaction for given runtime call, signed by given account.
+	fn sign_transaction(
+		genesis_hash: <Self::Chain as ChainBase>::Hash,
+		signer: &Self::AccountKeyPair,
+		signer_nonce: <Self::Chain as Chain>::Index,
+		call: <Self::Chain as Chain>::Call,
+	) -> Self::SignedTransaction;
+}
+
+impl<Block: BlockT> BlockWithJustification<Block::Header> for SignedBlock<Block> {
+	fn header(&self) -> Block::Header {
+		self.block.header().clone()
+	}
+
+	fn justification(&self) -> Option<&EncodedJustification> {
+		self.justifications
+			.as_ref()
+			.and_then(|j| j.get(sp_finality_grandpa::GRANDPA_ENGINE_ID))
+	}
+}

polkadot/bridges/relays/client-substrate/src/client.rs

@@ -0,0 +1,275 @@
+// 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/>.
+
+//! Substrate node client.
+
+use crate::chain::{Chain, ChainWithBalances};
+use crate::rpc::Substrate;
+use crate::{ConnectionParams, Error, Result};
+
+use async_std::sync::{Arc, Mutex};
+use codec::Decode;
+use frame_system::AccountInfo;
+use jsonrpsee_ws_client::{traits::SubscriptionClient, v2::params::JsonRpcParams, DeserializeOwned};
+use jsonrpsee_ws_client::{Subscription, WsClient as RpcClient, WsClientBuilder as RpcClientBuilder};
+use num_traits::Zero;
+use pallet_balances::AccountData;
+use sp_core::{storage::StorageKey, Bytes};
+use sp_trie::StorageProof;
+use sp_version::RuntimeVersion;
+
+const SUB_API_GRANDPA_AUTHORITIES: &str = "GrandpaApi_grandpa_authorities";
+const MAX_SUBSCRIPTION_CAPACITY: usize = 4096;
+
+/// Opaque justifications subscription type.
+pub type JustificationsSubscription = Subscription<Bytes>;
+
+/// Opaque GRANDPA authorities set.
+pub type OpaqueGrandpaAuthoritiesSet = Vec<u8>;
+
+/// Substrate client type.
+///
+/// Cloning `Client` is a cheap operation.
+pub struct Client<C: Chain> {
+	/// Client connection params.
+	params: ConnectionParams,
+	/// Substrate RPC client.
+	client: Arc<RpcClient>,
+	/// Genesis block hash.
+	genesis_hash: C::Hash,
+	/// 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<()>>,
+}
+
+impl<C: Chain> Clone for Client<C> {
+	fn clone(&self) -> Self {
+		Client {
+			params: self.params.clone(),
+			client: self.client.clone(),
+			genesis_hash: self.genesis_hash,
+			submit_signed_extrinsic_lock: self.submit_signed_extrinsic_lock.clone(),
+		}
+	}
+}
+
+impl<C: Chain> std::fmt::Debug for Client<C> {
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		fmt.debug_struct("Client")
+			.field("genesis_hash", &self.genesis_hash)
+			.finish()
+	}
+}
+
+impl<C: Chain> Client<C> {
+	/// Returns client that is able to call RPCs on Substrate node over websocket connection.
+	pub async fn new(params: ConnectionParams) -> Result<Self> {
+		let client = Self::build_client(params.clone()).await?;
+
+		let number: C::BlockNumber = Zero::zero();
+		let genesis_hash = Substrate::<C>::chain_get_block_hash(&*client, number).await?;
+
+		Ok(Self {
+			params,
+			client,
+			genesis_hash,
+			submit_signed_extrinsic_lock: Arc::new(Mutex::new(())),
+		})
+	}
+
+	/// Reopen client connection.
+	pub async fn reconnect(&mut self) -> Result<()> {
+		self.client = Self::build_client(self.params.clone()).await?;
+		Ok(())
+	}
+
+	/// Build client to use in connection.
+	async fn build_client(params: ConnectionParams) -> Result<Arc<RpcClient>> {
+		let uri = format!(
+			"{}://{}:{}",
+			if params.secure { "wss" } else { "ws" },
+			params.host,
+			params.port,
+		);
+		let client = RpcClientBuilder::default()
+			.max_notifs_per_subscription(MAX_SUBSCRIPTION_CAPACITY)
+			.build(&uri)
+			.await?;
+
+		Ok(Arc::new(client))
+	}
+}
+
+impl<C: Chain> Client<C> {
+	/// Returns true if client is connected to at least one peer and is in synced state.
+	pub async fn ensure_synced(&self) -> Result<()> {
+		let health = Substrate::<C>::system_health(&*self.client).await?;
+		let is_synced = !health.is_syncing && (!health.should_have_peers || health.peers > 0);
+		if is_synced {
+			Ok(())
+		} else {
+			Err(Error::ClientNotSynced(health))
+		}
+	}
+
+	/// Return hash of the genesis block.
+	pub fn genesis_hash(&self) -> &C::Hash {
+		&self.genesis_hash
+	}
+
+	/// Return hash of the best finalized block.
+	pub async fn best_finalized_header_hash(&self) -> Result<C::Hash> {
+		Ok(Substrate::<C>::chain_get_finalized_head(&*self.client).await?)
+	}
+
+	/// Returns the best Substrate header.
+	pub async fn best_header(&self) -> Result<C::Header>
+	where
+		C::Header: DeserializeOwned,
+	{
+		Ok(Substrate::<C>::chain_get_header(&*self.client, None).await?)
+	}
+
+	/// Get a Substrate block from its hash.
+	pub async fn get_block(&self, block_hash: Option<C::Hash>) -> Result<C::SignedBlock> {
+		Ok(Substrate::<C>::chain_get_block(&*self.client, block_hash).await?)
+	}
+
+	/// Get a Substrate header by its hash.
+	pub async fn header_by_hash(&self, block_hash: C::Hash) -> Result<C::Header>
+	where
+		C::Header: DeserializeOwned,
+	{
+		Ok(Substrate::<C>::chain_get_header(&*self.client, block_hash).await?)
+	}
+
+	/// Get a Substrate block hash by its number.
+	pub async fn block_hash_by_number(&self, number: C::BlockNumber) -> Result<C::Hash> {
+		Ok(Substrate::<C>::chain_get_block_hash(&*self.client, number).await?)
+	}
+
+	/// Get a Substrate header by its number.
+	pub async fn header_by_number(&self, block_number: C::BlockNumber) -> Result<C::Header>
+	where
+		C::Header: DeserializeOwned,
+	{
+		let block_hash = Self::block_hash_by_number(self, block_number).await?;
+		Ok(Self::header_by_hash(self, block_hash).await?)
+	}
+
+	/// Return runtime version.
+	pub async fn runtime_version(&self) -> Result<RuntimeVersion> {
+		Ok(Substrate::<C>::state_runtime_version(&*self.client).await?)
+	}
+
+	/// Read value from runtime storage.
+	pub async fn storage_value<T: Decode>(&self, storage_key: StorageKey) -> Result<Option<T>> {
+		Substrate::<C>::state_get_storage(&*self.client, storage_key)
+			.await?
+			.map(|encoded_value| T::decode(&mut &encoded_value.0[..]).map_err(Error::ResponseParseFailed))
+			.transpose()
+	}
+
+	/// Return native tokens balance of the account.
+	pub async fn free_native_balance(&self, account: C::AccountId) -> Result<C::NativeBalance>
+	where
+		C: ChainWithBalances,
+	{
+		let storage_key = C::account_info_storage_key(&account);
+		let encoded_account_data = Substrate::<C>::state_get_storage(&*self.client, storage_key)
+			.await?
+			.ok_or(Error::AccountDoesNotExist)?;
+		let decoded_account_data =
+			AccountInfo::<C::Index, AccountData<C::NativeBalance>>::decode(&mut &encoded_account_data.0[..])
+				.map_err(Error::ResponseParseFailed)?;
+		Ok(decoded_account_data.data.free)
+	}
+
+	/// Get the nonce of the given Substrate account.
+	///
+	/// Note: It's the caller's responsibility to make sure `account` is a valid ss58 address.
+	pub async fn next_account_index(&self, account: C::AccountId) -> Result<C::Index> {
+		Ok(Substrate::<C>::system_account_next_index(&*self.client, account).await?)
+	}
+
+	/// Submit unsigned extrinsic for inclusion in a block.
+	///
+	/// Note: The given transaction needs to be SCALE encoded beforehand.
+	pub async fn submit_unsigned_extrinsic(&self, transaction: Bytes) -> Result<C::Hash> {
+		let tx_hash = Substrate::<C>::author_submit_extrinsic(&*self.client, transaction).await?;
+		log::trace!(target: "bridge", "Sent transaction to Substrate node: {:?}", tx_hash);
+		Ok(tx_hash)
+	}
+
+	/// 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.
+	pub async fn submit_signed_extrinsic(
+		&self,
+		extrinsic_signer: C::AccountId,
+		prepare_extrinsic: impl FnOnce(C::Index) -> Bytes,
+	) -> Result<C::Hash> {
+		let _guard = self.submit_signed_extrinsic_lock.lock().await;
+		let transaction_nonce = self.next_account_index(extrinsic_signer).await?;
+		let extrinsic = prepare_extrinsic(transaction_nonce);
+		let tx_hash = Substrate::<C>::author_submit_extrinsic(&*self.client, extrinsic).await?;
+		log::trace!(target: "bridge", "Sent transaction to {} node: {:?}", C::NAME, tx_hash);
+		Ok(tx_hash)
+	}
+
+	/// Get the GRANDPA authority set at given block.
+	pub async fn grandpa_authorities_set(&self, block: C::Hash) -> Result<OpaqueGrandpaAuthoritiesSet> {
+		let call = SUB_API_GRANDPA_AUTHORITIES.to_string();
+		let data = Bytes(Vec::new());
+
+		let encoded_response = Substrate::<C>::state_call(&*self.client, call, data, Some(block)).await?;
+		let authority_list = encoded_response.0;
+
+		Ok(authority_list)
+	}
+
+	/// Execute runtime call at given block.
+	pub async fn state_call(&self, method: String, data: Bytes, at_block: Option<C::Hash>) -> Result<Bytes> {
+		Substrate::<C>::state_call(&*self.client, method, data, at_block)
+			.await
+			.map_err(Into::into)
+	}
+
+	/// Returns storage proof of given storage keys.
+	pub async fn prove_storage(&self, keys: Vec<StorageKey>, at_block: C::Hash) -> Result<StorageProof> {
+		Substrate::<C>::state_prove_storage(&*self.client, keys, Some(at_block))
+			.await
+			.map(|proof| StorageProof::new(proof.proof.into_iter().map(|b| b.0).collect()))
+			.map_err(Into::into)
+	}
+
+	/// Return new justifications stream.
+	pub async fn subscribe_justifications(&self) -> Result<JustificationsSubscription> {
+		Ok(self
+			.client
+			.subscribe(
+				"grandpa_subscribeJustifications",
+				JsonRpcParams::NoParams,
+				"grandpa_unsubscribeJustifications",
+			)
+			.await?)
+	}
+}

polkadot/bridges/relays/client-substrate/src/error.rs

@@ -0,0 +1,105 @@
+// 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/>.
+
+//! Substrate node RPC errors.
+
+use jsonrpsee_ws_client::Error as RpcError;
+use relay_utils::MaybeConnectionError;
+use sc_rpc_api::system::Health;
+
+/// Result type used by Substrate client.
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Errors that can occur only when interacting with
+/// a Substrate node through RPC.
+#[derive(Debug)]
+pub enum Error {
+	/// An error that can occur when making a request to
+	/// an JSON-RPC server.
+	RpcError(RpcError),
+	/// The response from the server could not be SCALE decoded.
+	ResponseParseFailed(codec::Error),
+	/// The Substrate bridge pallet has not yet been initialized.
+	UninitializedBridgePallet,
+	/// Account does not exist on the chain.
+	AccountDoesNotExist,
+	/// Runtime storage is missing mandatory ":code:" entry.
+	MissingMandatoryCodeEntry,
+	/// The client we're connected to is not synced, so we can't rely on its state.
+	ClientNotSynced(Health),
+	/// An error has happened when we have tried to parse storage proof.
+	StorageProofError(bp_runtime::StorageProofError),
+	/// Custom logic error.
+	Custom(String),
+}
+
+impl std::error::Error for Error {
+	fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+		match self {
+			Self::RpcError(ref e) => Some(e),
+			Self::ResponseParseFailed(ref e) => Some(e),
+			Self::UninitializedBridgePallet => None,
+			Self::AccountDoesNotExist => None,
+			Self::MissingMandatoryCodeEntry => None,
+			Self::ClientNotSynced(_) => None,
+			Self::StorageProofError(_) => None,
+			Self::Custom(_) => None,
+		}
+	}
+}
+
+impl From<RpcError> for Error {
+	fn from(error: RpcError) -> Self {
+		Error::RpcError(error)
+	}
+}
+
+impl MaybeConnectionError for Error {
+	fn is_connection_error(&self) -> bool {
+		matches!(
+			*self,
+			Error::RpcError(RpcError::TransportError(_))
+				// right now if connection to the ws server is dropped (after it is already established),
+				// we're getting this error
+				| Error::RpcError(RpcError::Internal(_))
+				| Error::RpcError(RpcError::RestartNeeded(_))
+				| Error::ClientNotSynced(_),
+		)
+	}
+}
+
+impl std::fmt::Display for Error {
+	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+		let s = match self {
+			Self::RpcError(e) => e.to_string(),
+			Self::ResponseParseFailed(e) => e.to_string(),
+			Self::UninitializedBridgePallet => "The Substrate bridge pallet has not been initialized yet.".into(),
+			Self::AccountDoesNotExist => "Account does not exist on the chain".into(),
+			Self::MissingMandatoryCodeEntry => "Mandatory :code: entry is missing from runtime storage".into(),
+			Self::StorageProofError(e) => format!("Error when parsing storage proof: {:?}", e),
+			Self::ClientNotSynced(health) => format!("Substrate client is not synced: {}", health),
+			Self::Custom(e) => e.clone(),
+		};
+
+		write!(f, "{}", s)
+	}
+}
+
+impl From<Error> for String {
+	fn from(error: Error) -> String {
+		error.to_string()
+	}
+}

polkadot/bridges/relays/client-substrate/src/finality_source.rs

@@ -0,0 +1,135 @@
+// 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/>.
+
+//! Default generic implementation of finality source for basic Substrate client.
+
+use crate::chain::{BlockWithJustification, Chain};
+use crate::client::Client;
+use crate::error::Error;
+use crate::sync_header::SyncHeader;
+
+use async_trait::async_trait;
+use bp_header_chain::justification::GrandpaJustification;
+use codec::Decode;
+use finality_relay::{FinalitySyncPipeline, SourceClient, SourceHeader};
+use futures::stream::{unfold, Stream, StreamExt};
+use relay_utils::relay_loop::Client as RelayClient;
+use sp_runtime::traits::Header as HeaderT;
+use std::{marker::PhantomData, pin::Pin};
+
+/// Substrate node as finality source.
+pub struct FinalitySource<C: Chain, P> {
+	client: Client<C>,
+	_phantom: PhantomData<P>,
+}
+
+impl<C: Chain, P> FinalitySource<C, P> {
+	/// Create new headers source using given client.
+	pub fn new(client: Client<C>) -> Self {
+		FinalitySource {
+			client,
+			_phantom: Default::default(),
+		}
+	}
+}
+
+impl<C: Chain, P> Clone for FinalitySource<C, P> {
+	fn clone(&self) -> Self {
+		FinalitySource {
+			client: self.client.clone(),
+			_phantom: Default::default(),
+		}
+	}
+}
+
+#[async_trait]
+impl<C: Chain, P: FinalitySyncPipeline> RelayClient for FinalitySource<C, P> {
+	type Error = Error;
+
+	async fn reconnect(&mut self) -> Result<(), Error> {
+		self.client.reconnect().await
+	}
+}
+
+#[async_trait]
+impl<C, P> SourceClient<P> for FinalitySource<C, P>
+where
+	C: Chain,
+	C::BlockNumber: relay_utils::BlockNumberBase,
+	P: FinalitySyncPipeline<
+		Hash = C::Hash,
+		Number = C::BlockNumber,
+		Header = SyncHeader<C::Header>,
+		FinalityProof = GrandpaJustification<C::Header>,
+	>,
+	P::Header: SourceHeader<C::BlockNumber>,
+{
+	type FinalityProofsStream = Pin<Box<dyn Stream<Item = GrandpaJustification<C::Header>> + Send>>;
+
+	async fn best_finalized_block_number(&self) -> Result<P::Number, Error> {
+		// we **CAN** continue to relay finality proofs if source node is out of sync, because
+		// target node may be missing proofs that are already available at the source
+		let finalized_header_hash = self.client.best_finalized_header_hash().await?;
+		let finalized_header = self.client.header_by_hash(finalized_header_hash).await?;
+		Ok(*finalized_header.number())
+	}
+
+	async fn header_and_finality_proof(
+		&self,
+		number: P::Number,
+	) -> Result<(P::Header, Option<P::FinalityProof>), Error> {
+		let header_hash = self.client.block_hash_by_number(number).await?;
+		let signed_block = self.client.get_block(Some(header_hash)).await?;
+
+		let justification = signed_block
+			.justification()
+			.map(|raw_justification| GrandpaJustification::<C::Header>::decode(&mut raw_justification.as_slice()))
+			.transpose()
+			.map_err(Error::ResponseParseFailed)?;
+
+		Ok((signed_block.header().into(), justification))
+	}
+
+	async fn finality_proofs(&self) -> Result<Self::FinalityProofsStream, Error> {
+		Ok(unfold(
+			self.client.clone().subscribe_justifications().await?,
+			move |mut subscription| async move {
+				loop {
+					let next_justification = subscription.next().await?;
+					let decoded_justification =
+						GrandpaJustification::<C::Header>::decode(&mut &next_justification.0[..]);
+
+					let justification = match decoded_justification {
+						Ok(j) => j,
+						Err(err) => {
+							log::error!(
+								target: "bridge",
+								"Failed to decode justification target from the {} justifications stream: {:?}",
+								P::SOURCE_NAME,
+								err,
+							);
+
+							continue;
+						}
+					};
+
+					return Some((justification, subscription));
+				}
+			},
+		)
+		.boxed())
+	}
+}

polkadot/bridges/relays/client-substrate/src/guard.rs

@@ -0,0 +1,373 @@
+// 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/>.
+
+//! Pallet provides a set of guard functions that are running in background threads
+//! and are aborting process if some condition fails.
+
+use crate::{Chain, ChainWithBalances, Client};
+
+use async_trait::async_trait;
+use num_traits::CheckedSub;
+use sp_version::RuntimeVersion;
+use std::{
+	collections::VecDeque,
+	time::{Duration, Instant},
+};
+
+/// Guards environment.
+#[async_trait]
+pub trait Environment<C: ChainWithBalances>: Send + Sync + 'static {
+	/// Return current runtime version.
+	async fn runtime_version(&mut self) -> Result<RuntimeVersion, String>;
+	/// Return free native balance of the account on the chain.
+	async fn free_native_balance(&mut self, account: C::AccountId) -> Result<C::NativeBalance, String>;
+
+	/// 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: ChainWithBalances>(mut env: impl Environment<C>, expected_spec_version: u32) {
+	async_std::task::spawn(async move {
+		loop {
+			let actual_spec_version = env.runtime_version().await;
+			match actual_spec_version {
+				Ok(version) if version.spec_version == expected_spec_version => (),
+				Ok(version) => {
+					log::error!(
+						target: "bridge-guard",
+						"{} runtime spec version has changed from {} to {}. Aborting relay",
+						C::NAME,
+						expected_spec_version,
+						version.spec_version,
+					);
+
+					env.abort().await;
+				}
+				Err(error) => log::warn!(
+					target: "bridge-guard",
+					"Failed to read {} runtime version: {:?}. Relay may need to be stopped manually",
+					C::NAME,
+					error,
+				),
+			}
+
+			env.sleep(conditions_check_delay::<C>()).await;
+		}
+	});
+}
+
+/// Abort if, during a 24 hours, free balance of given account is decreased at least by given value.
+/// Other components may increase (or decrease) balance of account and it WILL affect logic of the guard.
+pub fn abort_when_account_balance_decreased<C: ChainWithBalances>(
+	mut env: impl Environment<C>,
+	account_id: C::AccountId,
+	maximal_decrease: C::NativeBalance,
+) {
+	const DAY: Duration = Duration::from_secs(60 * 60 * 24);
+
+	async_std::task::spawn(async move {
+		let mut balances = VecDeque::new();
+
+		loop {
+			let current_time = env.now();
+
+			// remember balances that are beyound 24h border
+			let time_border = current_time - DAY;
+			while balances.front().map(|(time, _)| *time < time_border).unwrap_or(false) {
+				balances.pop_front();
+			}
+
+			// read balance of the account
+			let current_balance = env.free_native_balance(account_id.clone()).await;
+
+			// remember balance and check difference
+			match current_balance {
+				Ok(current_balance) => {
+					// remember balance
+					balances.push_back((current_time, current_balance));
+
+					// check if difference between current and oldest balance is too large
+					let (oldest_time, oldest_balance) =
+						balances.front().expect("pushed to queue couple of lines above; qed");
+					let balances_difference = oldest_balance.checked_sub(&current_balance);
+					if balances_difference > Some(maximal_decrease) {
+						log::error!(
+							target: "bridge-guard",
+							"Balance of {} account {:?} has decreased from {:?} to {:?} in {} minutes. Aborting relay",
+							C::NAME,
+							account_id,
+							oldest_balance,
+							current_balance,
+							current_time.duration_since(*oldest_time).as_secs() / 60,
+						);
+
+						env.abort().await;
+					}
+				}
+				Err(error) => {
+					log::warn!(
+						target: "bridge-guard",
+						"Failed to read {} account {:?} balance: {:?}. Relay may need to be stopped manually",
+						C::NAME,
+						account_id,
+						error,
+					);
+				}
+			};
+
+			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: ChainWithBalances> Environment<C> for Client<C> {
+	async fn runtime_version(&mut self) -> Result<RuntimeVersion, String> {
+		Client::<C>::runtime_version(self).await.map_err(|e| e.to_string())
+	}
+
+	async fn free_native_balance(&mut self, account: C::AccountId) -> Result<C::NativeBalance, String> {
+		Client::<C>::free_native_balance(self, account)
+			.await
+			.map_err(|e| e.to_string())
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use futures::{
+		channel::mpsc::{unbounded, UnboundedReceiver, UnboundedSender},
+		future::FutureExt,
+		stream::StreamExt,
+		SinkExt,
+	};
+
+	#[derive(Debug, Clone)]
+	struct TestChain;
+
+	impl bp_runtime::Chain for TestChain {
+		type BlockNumber = u32;
+		type Hash = sp_core::H256;
+		type Hasher = sp_runtime::traits::BlakeTwo256;
+		type Header = sp_runtime::generic::Header<u32, sp_runtime::traits::BlakeTwo256>;
+	}
+
+	impl Chain for TestChain {
+		const NAME: &'static str = "Test";
+		const AVERAGE_BLOCK_INTERVAL: Duration = Duration::from_millis(1);
+
+		type AccountId = u32;
+		type Index = u32;
+		type SignedBlock =
+			sp_runtime::generic::SignedBlock<sp_runtime::generic::Block<Self::Header, sp_runtime::OpaqueExtrinsic>>;
+		type Call = ();
+	}
+
+	impl ChainWithBalances for TestChain {
+		type NativeBalance = u32;
+
+		fn account_info_storage_key(_account_id: &u32) -> sp_core::storage::StorageKey {
+			unreachable!()
+		}
+	}
+
+	struct TestEnvironment {
+		runtime_version_rx: UnboundedReceiver<RuntimeVersion>,
+		free_native_balance_rx: UnboundedReceiver<u32>,
+		slept_tx: UnboundedSender<()>,
+		aborted_tx: UnboundedSender<()>,
+	}
+
+	#[async_trait]
+	impl Environment<TestChain> for TestEnvironment {
+		async fn runtime_version(&mut self) -> Result<RuntimeVersion, String> {
+			Ok(self.runtime_version_rx.next().await.unwrap_or_default())
+		}
+
+		async fn free_native_balance(&mut self, _account: u32) -> Result<u32, String> {
+			Ok(self.free_native_balance_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),
+				(_free_native_balance_tx, free_native_balance_rx),
+				(slept_tx, mut slept_rx),
+				(aborted_tx, mut aborted_rx),
+			) = (unbounded(), unbounded(), unbounded(), unbounded());
+			abort_on_spec_version_change(
+				TestEnvironment {
+					runtime_version_rx,
+					free_native_balance_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),
+				(_free_native_balance_tx, free_native_balance_rx),
+				(slept_tx, mut slept_rx),
+				(aborted_tx, mut aborted_rx),
+			) = (unbounded(), unbounded(), unbounded(), unbounded());
+			abort_on_spec_version_change(
+				TestEnvironment {
+					runtime_version_rx,
+					free_native_balance_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());
+		});
+	}
+
+	#[test]
+	fn aborts_when_balance_is_too_low() {
+		async_std::task::block_on(async {
+			let (
+				(_runtime_version_tx, runtime_version_rx),
+				(mut free_native_balance_tx, free_native_balance_rx),
+				(slept_tx, mut slept_rx),
+				(aborted_tx, mut aborted_rx),
+			) = (unbounded(), unbounded(), unbounded(), unbounded());
+			abort_when_account_balance_decreased(
+				TestEnvironment {
+					runtime_version_rx,
+					free_native_balance_rx,
+					slept_tx,
+					aborted_tx,
+				},
+				0,
+				100,
+			);
+
+			// client responds with initial balance
+			free_native_balance_tx.send(1000).await.unwrap();
+
+			// then the guard sleeps
+			slept_rx.next().await;
+
+			// and then client responds with updated balance, which is too low
+			free_native_balance_tx.send(899).await.unwrap();
+
+			// then the `abort` function is called
+			aborted_rx.next().await;
+			// and we do not reach next `sleep` function call
+			assert!(slept_rx.next().now_or_never().is_none());
+		});
+	}
+
+	#[test]
+	fn does_not_aborts_when_balance_is_enough() {
+		async_std::task::block_on(async {
+			let (
+				(_runtime_version_tx, runtime_version_rx),
+				(mut free_native_balance_tx, free_native_balance_rx),
+				(slept_tx, mut slept_rx),
+				(aborted_tx, mut aborted_rx),
+			) = (unbounded(), unbounded(), unbounded(), unbounded());
+			abort_when_account_balance_decreased(
+				TestEnvironment {
+					runtime_version_rx,
+					free_native_balance_rx,
+					slept_tx,
+					aborted_tx,
+				},
+				0,
+				100,
+			);
+
+			// client responds with initial balance
+			free_native_balance_tx.send(1000).await.unwrap();
+
+			// then the guard sleeps
+			slept_rx.next().await;
+
+			// and then client responds with updated balance, which is enough
+			free_native_balance_tx.send(950).await.unwrap();
+
+			// then the `sleep` function is called
+			slept_rx.next().await;
+			// and `abort` is not called
+			assert!(aborted_rx.next().now_or_never().is_none());
+		});
+	}
+}

polkadot/bridges/relays/client-substrate/src/headers_source.rs

@@ -0,0 +1,108 @@
+// 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/>.
+
+//! Default generic implementation of headers source for basic Substrate client.
+
+use crate::chain::{BlockWithJustification, Chain};
+use crate::client::Client;
+use crate::error::Error;
+
+use async_trait::async_trait;
+use headers_relay::{
+	sync_loop::SourceClient,
+	sync_types::{HeaderIdOf, HeadersSyncPipeline, QueuedHeader, SourceHeader},
+};
+use relay_utils::relay_loop::Client as RelayClient;
+use sp_runtime::{traits::Header as HeaderT, EncodedJustification};
+use std::marker::PhantomData;
+
+/// Substrate node as headers source.
+pub struct HeadersSource<C: Chain, P> {
+	client: Client<C>,
+	_phantom: PhantomData<P>,
+}
+
+impl<C: Chain, P> HeadersSource<C, P> {
+	/// Create new headers source using given client.
+	pub fn new(client: Client<C>) -> Self {
+		HeadersSource {
+			client,
+			_phantom: Default::default(),
+		}
+	}
+}
+
+impl<C: Chain, P> Clone for HeadersSource<C, P> {
+	fn clone(&self) -> Self {
+		HeadersSource {
+			client: self.client.clone(),
+			_phantom: Default::default(),
+		}
+	}
+}
+
+#[async_trait]
+impl<C: Chain, P: HeadersSyncPipeline> RelayClient for HeadersSource<C, P> {
+	type Error = Error;
+
+	async fn reconnect(&mut self) -> Result<(), Error> {
+		self.client.reconnect().await
+	}
+}
+
+#[async_trait]
+impl<C, P> SourceClient<P> for HeadersSource<C, P>
+where
+	C: Chain,
+	C::BlockNumber: relay_utils::BlockNumberBase,
+	C::Header: Into<P::Header>,
+	P: HeadersSyncPipeline<Extra = (), Completion = EncodedJustification, Hash = C::Hash, Number = C::BlockNumber>,
+	P::Header: SourceHeader<C::Hash, C::BlockNumber>,
+{
+	async fn best_block_number(&self) -> Result<P::Number, Error> {
+		// we **CAN** continue to relay headers if source node is out of sync, because
+		// target node may be missing headers that are already available at the source
+		Ok(*self.client.best_header().await?.number())
+	}
+
+	async fn header_by_hash(&self, hash: P::Hash) -> Result<P::Header, Error> {
+		self.client
+			.header_by_hash(hash)
+			.await
+			.map(Into::into)
+			.map_err(Into::into)
+	}
+
+	async fn header_by_number(&self, number: P::Number) -> Result<P::Header, Error> {
+		self.client
+			.header_by_number(number)
+			.await
+			.map(Into::into)
+			.map_err(Into::into)
+	}
+
+	async fn header_completion(&self, id: HeaderIdOf<P>) -> Result<(HeaderIdOf<P>, Option<P::Completion>), Error> {
+		let hash = id.1;
+		let signed_block = self.client.get_block(Some(hash)).await?;
+		let grandpa_justification = signed_block.justification().cloned();
+
+		Ok((id, grandpa_justification))
+	}
+
+	async fn header_extra(&self, id: HeaderIdOf<P>, _header: QueuedHeader<P>) -> Result<(HeaderIdOf<P>, ()), Error> {
+		Ok((id, ()))
+	}
+}

polkadot/bridges/relays/client-substrate/src/lib.rs

@@ -0,0 +1,60 @@
+// 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 (Open) Ethereum node using RPC methods.
+
+#![warn(missing_docs)]
+
+mod chain;
+mod client;
+mod error;
+mod rpc;
+mod sync_header;
+
+pub mod finality_source;
+pub mod guard;
+pub mod headers_source;
+pub mod metrics;
+
+pub use crate::chain::{BlockWithJustification, Chain, ChainWithBalances, TransactionSignScheme};
+pub use crate::client::{Client, JustificationsSubscription, OpaqueGrandpaAuthoritiesSet};
+pub use crate::error::{Error, Result};
+pub use crate::sync_header::SyncHeader;
+pub use bp_runtime::{BlockNumberOf, Chain as ChainBase, HashOf, HeaderOf};
+
+/// Header id used by the chain.
+pub type HeaderIdOf<C> = relay_utils::HeaderId<HashOf<C>, BlockNumberOf<C>>;
+
+/// Substrate-over-websocket connection params.
+#[derive(Debug, Clone)]
+pub struct ConnectionParams {
+	/// Websocket server hostname.
+	pub host: String,
+	/// Websocket server TCP port.
+	pub port: u16,
+	/// Use secure websocket connection.
+	pub secure: bool,
+}
+
+impl Default for ConnectionParams {
+	fn default() -> Self {
+		ConnectionParams {
+			host: "localhost".into(),
+			port: 9944,
+			secure: false,
+		}
+	}
+}

polkadot/bridges/relays/client-substrate/src/metrics/float_storage_value.rs

@@ -0,0 +1,82 @@
+// 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::Chain;
+use crate::client::Client;
+
+use async_trait::async_trait;
+use codec::Decode;
+use relay_utils::metrics::{metric_name, register, Gauge, PrometheusError, Registry, StandaloneMetrics, F64};
+use sp_core::storage::StorageKey;
+use sp_runtime::{traits::UniqueSaturatedInto, FixedPointNumber};
+use std::time::Duration;
+
+/// Storage value update interval (in blocks).
+const UPDATE_INTERVAL_IN_BLOCKS: u32 = 5;
+
+/// Metric that represents fixed-point runtime storage value as float gauge.
+#[derive(Clone, Debug)]
+pub struct FloatStorageValueMetric<C: Chain, T: Clone> {
+	client: Client<C>,
+	storage_key: StorageKey,
+	maybe_default_value: Option<T>,
+	metric: Gauge<F64>,
+}
+
+impl<C: Chain, T: Decode + FixedPointNumber> FloatStorageValueMetric<C, T> {
+	/// Create new metric.
+	pub fn new(
+		registry: &Registry,
+		prefix: Option<&str>,
+		client: Client<C>,
+		storage_key: StorageKey,
+		maybe_default_value: Option<T>,
+		name: String,
+		help: String,
+	) -> Result<Self, PrometheusError> {
+		Ok(FloatStorageValueMetric {
+			client,
+			storage_key,
+			maybe_default_value,
+			metric: register(Gauge::new(metric_name(prefix, &name), help)?, registry)?,
+		})
+	}
+}
+
+#[async_trait]
+impl<C: Chain, T> StandaloneMetrics for FloatStorageValueMetric<C, T>
+where
+	T: 'static + Decode + Send + Sync + FixedPointNumber,
+{
+	fn update_interval(&self) -> Duration {
+		C::AVERAGE_BLOCK_INTERVAL * UPDATE_INTERVAL_IN_BLOCKS
+	}
+
+	async fn update(&self) {
+		relay_utils::metrics::set_gauge_value(
+			&self.metric,
+			self.client
+				.storage_value::<T>(self.storage_key.clone())
+				.await
+				.map(|maybe_storage_value| {
+					maybe_storage_value.or(self.maybe_default_value).map(|storage_value| {
+						storage_value.into_inner().unique_saturated_into() as f64
+							/ T::DIV.unique_saturated_into() as f64
+					})
+				}),
+		);
+	}
+}

polkadot/bridges/relays/client-substrate/src/metrics/mod.rs

@@ -0,0 +1,23 @@
+// 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 Substrate-specific metrics that may be exposed by relay.
+
+pub use float_storage_value::FloatStorageValueMetric;
+pub use storage_proof_overhead::StorageProofOverheadMetric;
+
+mod float_storage_value;
+mod storage_proof_overhead;

polkadot/bridges/relays/client-substrate/src/metrics/storage_proof_overhead.rs

@@ -0,0 +1,104 @@
+// 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::Chain;
+use crate::client::Client;
+use crate::error::Error;
+
+use async_trait::async_trait;
+use relay_utils::metrics::{metric_name, register, Gauge, PrometheusError, Registry, StandaloneMetrics, U64};
+use sp_core::storage::StorageKey;
+use sp_runtime::traits::Header as HeaderT;
+use sp_storage::well_known_keys::CODE;
+use std::time::Duration;
+
+/// Storage proof overhead update interval (in blocks).
+const UPDATE_INTERVAL_IN_BLOCKS: u32 = 100;
+
+/// Metric that represents extra size of storage proof as unsigned integer gauge.
+///
+/// There's one thing to keep in mind when using this metric: the overhead may be slightly
+/// different for other values, but this metric gives a good estimation.
+#[derive(Debug)]
+pub struct StorageProofOverheadMetric<C: Chain> {
+	client: Client<C>,
+	metric: Gauge<U64>,
+}
+
+impl<C: Chain> Clone for StorageProofOverheadMetric<C> {
+	fn clone(&self) -> Self {
+		StorageProofOverheadMetric {
+			client: self.client.clone(),
+			metric: self.metric.clone(),
+		}
+	}
+}
+
+impl<C: Chain> StorageProofOverheadMetric<C> {
+	/// Create new metric instance with given name and help.
+	pub fn new(
+		registry: &Registry,
+		prefix: Option<&str>,
+		client: Client<C>,
+		name: String,
+		help: String,
+	) -> Result<Self, PrometheusError> {
+		Ok(StorageProofOverheadMetric {
+			client,
+			metric: register(Gauge::new(metric_name(prefix, &name), help)?, registry)?,
+		})
+	}
+
+	/// Returns approximate storage proof size overhead.
+	async fn compute_storage_proof_overhead(&self) -> Result<usize, Error> {
+		let best_header_hash = self.client.best_finalized_header_hash().await?;
+		let best_header = self.client.header_by_hash(best_header_hash).await?;
+
+		let storage_proof = self
+			.client
+			.prove_storage(vec![StorageKey(CODE.to_vec())], best_header_hash)
+			.await?;
+		let storage_proof_size: usize = storage_proof.clone().iter_nodes().map(|n| n.len()).sum();
+
+		let storage_value_reader =
+			bp_runtime::StorageProofChecker::<C::Hasher>::new(*best_header.state_root(), storage_proof)
+				.map_err(Error::StorageProofError)?;
+		let maybe_encoded_storage_value = storage_value_reader
+			.read_value(CODE)
+			.map_err(Error::StorageProofError)?;
+		let encoded_storage_value_size = maybe_encoded_storage_value
+			.ok_or(Error::MissingMandatoryCodeEntry)?
+			.len();
+
+		Ok(storage_proof_size - encoded_storage_value_size)
+	}
+}
+
+#[async_trait]
+impl<C: Chain> StandaloneMetrics for StorageProofOverheadMetric<C> {
+	fn update_interval(&self) -> Duration {
+		C::AVERAGE_BLOCK_INTERVAL * UPDATE_INTERVAL_IN_BLOCKS
+	}
+
+	async fn update(&self) {
+		relay_utils::metrics::set_gauge_value(
+			&self.metric,
+			self.compute_storage_proof_overhead()
+				.await
+				.map(|overhead| Some(overhead as u64)),
+		);
+	}
+}

polkadot/bridges/relays/client-substrate/src/rpc.rs

@@ -0,0 +1,53 @@
+// 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 Substrate node RPC interface.
+
+use crate::chain::Chain;
+
+use sc_rpc_api::{state::ReadProof, system::Health};
+use sp_core::{
+	storage::{StorageData, StorageKey},
+	Bytes,
+};
+use sp_version::RuntimeVersion;
+
+jsonrpsee_proc_macros::rpc_client_api! {
+	pub(crate) Substrate<C: Chain> {
+		#[rpc(method = "system_health", positional_params)]
+		fn system_health() -> Health;
+		#[rpc(method = "chain_getHeader", positional_params)]
+		fn chain_get_header(block_hash: Option<C::Hash>) -> C::Header;
+		#[rpc(method = "chain_getFinalizedHead", positional_params)]
+		fn chain_get_finalized_head() -> C::Hash;
+		#[rpc(method = "chain_getBlock", positional_params)]
+		fn chain_get_block(block_hash: Option<C::Hash>) -> C::SignedBlock;
+		#[rpc(method = "chain_getBlockHash", positional_params)]
+		fn chain_get_block_hash(block_number: Option<C::BlockNumber>) -> C::Hash;
+		#[rpc(method = "system_accountNextIndex", positional_params)]
+		fn system_account_next_index(account_id: C::AccountId) -> C::Index;
+		#[rpc(method = "author_submitExtrinsic", positional_params)]
+		fn author_submit_extrinsic(extrinsic: Bytes) -> C::Hash;
+		#[rpc(method = "state_call", positional_params)]
+		fn state_call(method: String, data: Bytes, at_block: Option<C::Hash>) -> Bytes;
+		#[rpc(method = "state_getStorage", positional_params)]
+		fn state_get_storage(key: StorageKey) -> Option<StorageData>;
+		#[rpc(method = "state_getReadProof", positional_params)]
+		fn state_prove_storage(keys: Vec<StorageKey>, hash: Option<C::Hash>) -> ReadProof<C::Hash>;
+		#[rpc(method = "state_getRuntimeVersion", positional_params)]
+		fn state_runtime_version() -> RuntimeVersion;
+	}
+}

polkadot/bridges/relays/client-substrate/src/sync_header.rs

@@ -0,0 +1,73 @@
+// 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_chain::find_grandpa_authorities_scheduled_change;
+use finality_relay::SourceHeader as FinalitySourceHeader;
+use headers_relay::sync_types::SourceHeader;
+use num_traits::{CheckedSub, One};
+use relay_utils::HeaderId;
+use sp_runtime::traits::Header as HeaderT;
+
+/// Generic wrapper for `sp_runtime::traits::Header` based headers, that
+/// implements `headers_relay::sync_types::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> SourceHeader<Header::Hash, Header::Number> for SyncHeader<Header> {
+	fn id(&self) -> HeaderId<Header::Hash, Header::Number> {
+		relay_utils::HeaderId(*self.0.number(), self.hash())
+	}
+
+	fn parent_id(&self) -> HeaderId<Header::Hash, Header::Number> {
+		relay_utils::HeaderId(
+			self.number()
+				.checked_sub(&One::one())
+				.expect("should never be called for genesis header"),
+			*self.parent_hash(),
+		)
+	}
+}
+
+impl<Header: HeaderT> FinalitySourceHeader<Header::Number> for SyncHeader<Header> {
+	fn number(&self) -> Header::Number {
+		*self.0.number()
+	}
+
+	fn is_mandatory(&self) -> bool {
+		find_grandpa_authorities_scheduled_change(&self.0).is_some()
+	}
+}