Support Pallet Instances in Relay (#238)

* Sketch out how to support different bridge pallet instances

* Create a common interface for using pallet instances

* Start introducing generic instance parameter

Attemps to make the compiler happy, but I'm having second thoughts about
this approach. Commiting now as a way to have a checkpoint, but I think
I'm going to need to re-consider my approach here.

Ideally I want a change which introduces minimal changes, but this seems
to be propagating around the codebase in ways I don't want.

* Use trait objects instead of generics

* Implement traits for Boxed trait objects

This is done in order to statisfy trait bounds by types
which use these new trait objects

* Remove Clone usage for sync parameters

* Remove implementation of Default for sync params

* Require that BridgeInstance implements Debug

* Ensure that BridgeInstance trait implements Send/Sync

* Add documentation related to instances

* Rust Fmt

* Remove needless format

* Make instance CLI option case insensitive

* Replace `with_*` constructors with `new`

* Clean up usage of instance structs

* Enforce a default instance in the CLI params

* Build sync params as we process input from CLI

* Remove case insensitivity from sub-tx-mode

I think this should happen, but maybe as part of a different PR

* Process default Eth contract deployment config in CLI

* Build EthereumExchangeParams in CLI

* Process EthereumExchangeSubmitParams params in CLI

bridges/relays/ethereum/src/cli.yml

@@ -43,6 +43,17 @@ subcommands:
                 long: sub-signer-password
                 value_name: SUB_SIGNER_PASSWORD
                 help: The password for the SURI of secret key to use when transactions are submitted to the Substrate node.
+            - sub-pallet-instance: &sub-pallet-instance
+                long: instance
+                short: i
+                value_name: PALLET_INSTANCE
+                help: The instance of the bridge pallet the relay should follow.
+                takes_value: true
+                case_insensitive: true
+                possible_values:
+                  - Rialto
+                  - Kovan
+                default_value: Rialto
             - no-prometheus: &no-prometheus
                 long: no-prometheus
                 help: Do not expose a Prometheus metric endpoint.

bridges/relays/ethereum/src/ethereum_deploy_contract.rs

@@ -17,6 +17,7 @@
 use crate::ethereum_client::{
 	bridge_contract, EthereumConnectionParams, EthereumHighLevelRpc, EthereumRpcClient, EthereumSigningParams,
 };
+use crate::instances::BridgeInstance;
 use crate::rpc::SubstrateRpc;
 use crate::substrate_client::{SubstrateConnectionParams, SubstrateRpcClient};
 use crate::substrate_types::{Hash as SubstrateHash, Header as SubstrateHeader, SubstrateHeaderId};
@@ -29,50 +30,48 @@ use num_traits::Zero;
 #[derive(Debug)]
 pub struct EthereumDeployContractParams {
 	/// Ethereum connection params.
-	pub eth: EthereumConnectionParams,
+	pub eth_params: EthereumConnectionParams,
 	/// Ethereum signing params.
 	pub eth_sign: EthereumSigningParams,
 	/// Ethereum contract bytecode.
 	pub eth_contract_code: Vec<u8>,
 	/// Substrate connection params.
-	pub sub: SubstrateConnectionParams,
+	pub sub_params: SubstrateConnectionParams,
 	/// Initial authorities set id.
 	pub sub_initial_authorities_set_id: Option<u64>,
 	/// Initial authorities set.
 	pub sub_initial_authorities_set: Option<Vec<u8>>,
 	/// Initial header.
 	pub sub_initial_header: Option<Vec<u8>>,
-}
-
-impl Default for EthereumDeployContractParams {
-	fn default() -> Self {
-		EthereumDeployContractParams {
-			eth: Default::default(),
-			eth_sign: Default::default(),
-			eth_contract_code: hex::decode(include_str!("../res/substrate-bridge-bytecode.hex"))
-				.expect("code is hardcoded, thus valid; qed"),
-			sub: Default::default(),
-			sub_initial_authorities_set_id: None,
-			sub_initial_authorities_set: None,
-			sub_initial_header: None,
-		}
-	}
+	/// Instance of the bridge pallet being synchronized.
+	pub instance: Box<dyn BridgeInstance>,
 }
 
 /// Deploy Bridge contract on Ethereum chain.
 pub fn run(params: EthereumDeployContractParams) {
 	let mut local_pool = futures::executor::LocalPool::new();
 
-	let result = local_pool.run_until(async move {
-		let eth_client = EthereumRpcClient::new(params.eth);
-		let sub_client = SubstrateRpcClient::new(params.sub).await?;
+	let EthereumDeployContractParams {
+		eth_params,
+		eth_sign,
+		sub_params,
+		instance,
+		sub_initial_authorities_set_id,
+		sub_initial_authorities_set,
+		sub_initial_header,
+		eth_contract_code,
+	} = params;
 
-		let (initial_header_id, initial_header) = prepare_initial_header(&sub_client, params.sub_initial_header).await?;
-		let initial_set_id = params.sub_initial_authorities_set_id.unwrap_or(0);
+	let result = local_pool.run_until(async move {
+		let eth_client = EthereumRpcClient::new(eth_params);
+		let sub_client = SubstrateRpcClient::new(sub_params, instance).await?;
+
+		let (initial_header_id, initial_header) = prepare_initial_header(&sub_client, sub_initial_header).await?;
+		let initial_set_id = sub_initial_authorities_set_id.unwrap_or(0);
 		let initial_set = prepare_initial_authorities_set(
 			&sub_client,
 			initial_header_id.1,
-			params.sub_initial_authorities_set,
+			sub_initial_authorities_set,
 		).await?;
 
 		log::info!(
@@ -87,8 +86,8 @@ pub fn run(params: EthereumDeployContractParams) {
 
 		deploy_bridge_contract(
 			&eth_client,
-			&params.eth_sign,
-			params.eth_contract_code,
+			&eth_sign,
+			eth_contract_code,
 			initial_header,
 			initial_set_id,
 			initial_set,

bridges/relays/ethereum/src/ethereum_exchange.rs

@@ -26,6 +26,7 @@ use crate::exchange::{
 	TransactionProofPipeline,
 };
 use crate::exchange_loop::{run as run_loop, InMemoryStorage};
+use crate::instances::BridgeInstance;
 use crate::metrics::MetricsParams;
 use crate::rpc::{EthereumRpc, SubstrateRpc};
 use crate::rpc_errors::RpcError;
@@ -58,15 +59,17 @@ pub enum ExchangeRelayMode {
 #[derive(Debug)]
 pub struct EthereumExchangeParams {
 	/// Ethereum connection params.
-	pub eth: EthereumConnectionParams,
+	pub eth_params: EthereumConnectionParams,
 	/// Substrate connection params.
-	pub sub: SubstrateConnectionParams,
+	pub sub_params: SubstrateConnectionParams,
 	/// Substrate signing params.
 	pub sub_sign: SubstrateSigningParams,
 	/// Relay working mode.
 	pub mode: ExchangeRelayMode,
 	/// Metrics parameters.
 	pub metrics_params: Option<MetricsParams>,
+	/// Instance of the bridge pallet being synchronized.
+	pub instance: Box<dyn BridgeInstance>,
 }
 
 /// Ethereum to Substrate exchange pipeline.
@@ -253,18 +256,6 @@ impl TargetClient<EthereumToSubstrateExchange> for SubstrateTransactionsTarget {
 	}
 }
 
-impl Default for EthereumExchangeParams {
-	fn default() -> Self {
-		EthereumExchangeParams {
-			eth: Default::default(),
-			sub: Default::default(),
-			sub_sign: Default::default(),
-			mode: ExchangeRelayMode::Auto(None),
-			metrics_params: Some(Default::default()),
-		}
-	}
-}
-
 /// Relay exchange transaction proof(s) to Substrate node.
 pub fn run(params: EthereumExchangeParams) {
 	match params.mode {
@@ -279,14 +270,22 @@ pub fn run(params: EthereumExchangeParams) {
 fn run_single_transaction_relay(params: EthereumExchangeParams, eth_tx_hash: H256) {
 	let mut local_pool = futures::executor::LocalPool::new();
 
+	let EthereumExchangeParams {
+		eth_params,
+		sub_params,
+		sub_sign,
+		instance,
+		..
+	} = params;
+
 	let result = local_pool.run_until(async move {
-		let eth_client = EthereumRpcClient::new(params.eth);
-		let sub_client = SubstrateRpcClient::new(params.sub).await?;
+		let eth_client = EthereumRpcClient::new(eth_params);
+		let sub_client = SubstrateRpcClient::new(sub_params, instance).await?;
 
 		let source = EthereumTransactionsSource { client: eth_client };
 		let target = SubstrateTransactionsTarget {
 			client: sub_client,
-			sign_params: params.sub_sign,
+			sign_params: sub_sign,
 		};
 
 		relay_single_transaction_proof(&source, &target, eth_tx_hash).await
@@ -313,9 +312,18 @@ fn run_single_transaction_relay(params: EthereumExchangeParams, eth_tx_hash: H25
 
 /// Run auto-relay loop.
 fn run_auto_transactions_relay_loop(params: EthereumExchangeParams, eth_start_with_block_number: Option<u64>) {
+	let EthereumExchangeParams {
+		eth_params,
+		sub_params,
+		sub_sign,
+		metrics_params,
+		instance,
+		..
+	} = params;
+
 	let do_run_loop = move || -> Result<(), String> {
-		let eth_client = EthereumRpcClient::new(params.eth);
-		let sub_client = async_std::task::block_on(SubstrateRpcClient::new(params.sub))
+		let eth_client = EthereumRpcClient::new(eth_params);
+		let sub_client = async_std::task::block_on(SubstrateRpcClient::new(sub_params, instance))
 			.map_err(|err| format!("Error starting Substrate client: {:?}", err))?;
 
 		let eth_start_with_block_number = match eth_start_with_block_number {
@@ -337,9 +345,9 @@ fn run_auto_transactions_relay_loop(params: EthereumExchangeParams, eth_start_wi
 			EthereumTransactionsSource { client: eth_client },
 			SubstrateTransactionsTarget {
 				client: sub_client,
-				sign_params: params.sub_sign,
+				sign_params: sub_sign,
 			},
-			params.metrics_params,
+			metrics_params,
 			futures::future::pending(),
 		);
 

bridges/relays/ethereum/src/ethereum_exchange_submit.rs

@@ -21,7 +21,6 @@ use crate::ethereum_types::{CallRequest, U256};
 use crate::rpc::EthereumRpc;
 
 use bridge_node_runtime::exchange::LOCK_FUNDS_ADDRESS;
-use hex_literal::hex;
 use sp_bridge_eth_poa::{
 	signatures::{SecretKey, SignTransaction},
 	UnsignedTransaction,
@@ -31,7 +30,7 @@ use sp_bridge_eth_poa::{
 #[derive(Debug)]
 pub struct EthereumExchangeSubmitParams {
 	/// Ethereum connection params.
-	pub eth: EthereumConnectionParams,
+	pub eth_params: EthereumConnectionParams,
 	/// Ethereum signing params.
 	pub eth_sign: EthereumSigningParams,
 	/// Ethereum signer nonce.
@@ -42,28 +41,24 @@ pub struct EthereumExchangeSubmitParams {
 	pub sub_recipient: [u8; 32],
 }
 
-impl Default for EthereumExchangeSubmitParams {
-	fn default() -> Self {
-		EthereumExchangeSubmitParams {
-			eth: Default::default(),
-			eth_sign: Default::default(),
-			eth_nonce: None,
-			eth_amount: 1_000_000_000_000_000_000_u64.into(), // 1 ETH
-			sub_recipient: hex!("1cbd2d43530a44705ad088af313e18f80b53ef16b36177cd4b77b846f2a5f07c"), // ferdie
-		}
-	}
-}
-
 /// Submit single Ethereum -> Substrate exchange transaction.
 pub fn run(params: EthereumExchangeSubmitParams) {
 	let mut local_pool = futures::executor::LocalPool::new();
 
-	let result: Result<_, String> = local_pool.run_until(async move {
-		let eth_client = EthereumRpcClient::new(params.eth);
+	let EthereumExchangeSubmitParams {
+		eth_params,
+		eth_sign,
+		eth_nonce,
+		eth_amount,
+		sub_recipient,
+	} = params;
 
-		let eth_signer_address = params.eth_sign.signer.address();
-		let sub_recipient_encoded = params.sub_recipient;
-		let nonce = match params.eth_nonce {
+	let result: Result<_, String> = local_pool.run_until(async move {
+		let eth_client = EthereumRpcClient::new(eth_params);
+
+		let eth_signer_address = eth_sign.signer.address();
+		let sub_recipient_encoded = sub_recipient;
+		let nonce = match eth_nonce {
 			Some(eth_nonce) => eth_nonce,
 			None => eth_client
 				.account_nonce(eth_signer_address)
@@ -74,7 +69,7 @@ pub fn run(params: EthereumExchangeSubmitParams) {
 			.estimate_gas(CallRequest {
 				from: Some(eth_signer_address),
 				to: Some(LOCK_FUNDS_ADDRESS.into()),
-				value: Some(params.eth_amount),
+				value: Some(eth_amount),
 				data: Some(sub_recipient_encoded.to_vec().into()),
 				..Default::default()
 			})
@@ -82,16 +77,16 @@ pub fn run(params: EthereumExchangeSubmitParams) {
 			.map_err(|err| format!("error estimating gas requirements: {:?}", err))?;
 		let eth_tx_unsigned = UnsignedTransaction {
 			nonce,
-			gas_price: params.eth_sign.gas_price,
+			gas_price: eth_sign.gas_price,
 			gas,
 			to: Some(LOCK_FUNDS_ADDRESS.into()),
-			value: params.eth_amount,
+			value: eth_amount,
 			payload: sub_recipient_encoded.to_vec(),
 		};
 		let eth_tx_signed = eth_tx_unsigned.clone().sign_by(
-			&SecretKey::parse(params.eth_sign.signer.secret().as_fixed_bytes())
+			&SecretKey::parse(eth_sign.signer.secret().as_fixed_bytes())
 				.expect("key is accepted by secp256k1::KeyPair and thus is valid; qed"),
-			Some(params.eth_sign.chain_id),
+			Some(eth_sign.chain_id),
 		);
 		eth_client
 			.submit_transaction(eth_tx_signed)

bridges/relays/ethereum/src/ethereum_sync_loop.rs

@@ -18,6 +18,7 @@
 
 use crate::ethereum_client::{EthereumConnectionParams, EthereumHighLevelRpc, EthereumRpcClient};
 use crate::ethereum_types::{EthereumHeaderId, EthereumHeadersSyncPipeline, Header, QueuedEthereumHeader, Receipt};
+use crate::instances::BridgeInstance;
 use crate::metrics::MetricsParams;
 use crate::rpc::{EthereumRpc, SubstrateRpc};
 use crate::rpc_errors::RpcError;
@@ -32,57 +33,45 @@ use crate::sync_types::{SourceHeader, SubmittedHeaders};
 use async_trait::async_trait;
 use web3::types::H256;
 
+use std::fmt::Debug;
 use std::{collections::HashSet, time::Duration};
 
-/// Interval at which we check new Ethereum headers when we are synced/almost synced.
-const ETHEREUM_TICK_INTERVAL: Duration = Duration::from_secs(10);
-/// Interval at which we check new Substrate blocks.
-const SUBSTRATE_TICK_INTERVAL: Duration = Duration::from_secs(5);
-/// Max number of headers in single submit transaction.
-const MAX_HEADERS_IN_SINGLE_SUBMIT: usize = 32;
-/// Max total size of headers in single submit transaction. This only affects signed
-/// submissions, when several headers are submitted at once. 4096 is the maximal **expected**
-/// size of the Ethereum header + transactions receipts (if they're required).
-const MAX_HEADERS_SIZE_IN_SINGLE_SUBMIT: usize = MAX_HEADERS_IN_SINGLE_SUBMIT * 4096;
-/// Max Ethereum headers we want to have in all 'before-submitted' states.
-const MAX_FUTURE_HEADERS_TO_DOWNLOAD: usize = 128;
-/// Max Ethereum headers count we want to have in 'submitted' state.
-const MAX_SUBMITTED_HEADERS: usize = 128;
-/// Max depth of in-memory headers in all states. Past this depth they will be forgotten (pruned).
-const PRUNE_DEPTH: u32 = 4096;
+pub mod consts {
+	use super::*;
+
+	/// Interval at which we check new Ethereum headers when we are synced/almost synced.
+	pub const ETHEREUM_TICK_INTERVAL: Duration = Duration::from_secs(10);
+	/// Interval at which we check new Substrate blocks.
+	pub const SUBSTRATE_TICK_INTERVAL: Duration = Duration::from_secs(5);
+	/// Max number of headers in single submit transaction.
+	pub const MAX_HEADERS_IN_SINGLE_SUBMIT: usize = 32;
+	/// Max total size of headers in single submit transaction. This only affects signed
+	/// submissions, when several headers are submitted at once. 4096 is the maximal **expected**
+	/// size of the Ethereum header + transactions receipts (if they're required).
+	pub const MAX_HEADERS_SIZE_IN_SINGLE_SUBMIT: usize = MAX_HEADERS_IN_SINGLE_SUBMIT * 4096;
+	/// Max Ethereum headers we want to have in all 'before-submitted' states.
+	pub const MAX_FUTURE_HEADERS_TO_DOWNLOAD: usize = 128;
+	/// Max Ethereum headers count we want to have in 'submitted' state.
+	pub const MAX_SUBMITTED_HEADERS: usize = 128;
+	/// Max depth of in-memory headers in all states. Past this depth they will be forgotten (pruned).
+	pub const PRUNE_DEPTH: u32 = 4096;
+}
 
 /// Ethereum synchronization parameters.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct EthereumSyncParams {
 	/// Ethereum connection params.
-	pub eth: EthereumConnectionParams,
+	pub eth_params: EthereumConnectionParams,
 	/// Substrate connection params.
-	pub sub: SubstrateConnectionParams,
+	pub sub_params: SubstrateConnectionParams,
 	/// Substrate signing params.
 	pub sub_sign: SubstrateSigningParams,
 	/// Synchronization parameters.
 	pub sync_params: HeadersSyncParams,
 	/// Metrics parameters.
 	pub metrics_params: Option<MetricsParams>,
-}
-
-impl Default for EthereumSyncParams {
-	fn default() -> Self {
-		EthereumSyncParams {
-			eth: Default::default(),
-			sub: Default::default(),
-			sub_sign: Default::default(),
-			sync_params: HeadersSyncParams {
-				max_future_headers_to_download: MAX_FUTURE_HEADERS_TO_DOWNLOAD,
-				max_headers_in_submitted_status: MAX_SUBMITTED_HEADERS,
-				max_headers_in_single_submit: MAX_HEADERS_IN_SINGLE_SUBMIT,
-				max_headers_size_in_single_submit: MAX_HEADERS_SIZE_IN_SINGLE_SUBMIT,
-				prune_depth: PRUNE_DEPTH,
-				target_tx_mode: TargetTransactionMode::Signed,
-			},
-			metrics_params: Some(Default::default()),
-		}
-	}
+	/// Instance of the bridge pallet being synchronized.
+	pub instance: Box<dyn BridgeInstance>,
 }
 
 /// Ethereum client as headers source.
@@ -190,26 +179,33 @@ impl TargetClient<EthereumHeadersSyncPipeline> for SubstrateHeadersTarget {
 
 /// Run Ethereum headers synchronization.
 pub fn run(params: EthereumSyncParams) -> Result<(), RpcError> {
-	let sub_params = params.clone();
+	let EthereumSyncParams {
+		eth_params,
+		sub_params,
+		sub_sign,
+		sync_params,
+		metrics_params,
+		instance,
+	} = params;
 
-	let eth_client = EthereumRpcClient::new(params.eth);
-	let sub_client = async_std::task::block_on(async { SubstrateRpcClient::new(sub_params.sub).await })?;
+	let eth_client = EthereumRpcClient::new(eth_params);
+	let sub_client = async_std::task::block_on(async { SubstrateRpcClient::new(sub_params, instance).await })?;
 
-	let sign_sub_transactions = match params.sync_params.target_tx_mode {
+	let sign_sub_transactions = match sync_params.target_tx_mode {
 		TargetTransactionMode::Signed | TargetTransactionMode::Backup => true,
 		TargetTransactionMode::Unsigned => false,
 	};
 
 	let source = EthereumHeadersSource::new(eth_client);
-	let target = SubstrateHeadersTarget::new(sub_client, sign_sub_transactions, params.sub_sign);
+	let target = SubstrateHeadersTarget::new(sub_client, sign_sub_transactions, sub_sign);
 
 	crate::sync_loop::run(
 		source,
-		ETHEREUM_TICK_INTERVAL,
+		consts::ETHEREUM_TICK_INTERVAL,
 		target,
-		SUBSTRATE_TICK_INTERVAL,
-		params.sync_params,
-		params.metrics_params,
+		consts::SUBSTRATE_TICK_INTERVAL,
+		sync_params,
+		metrics_params,
 		futures::future::pending(),
 	);
 

bridges/relays/ethereum/src/instances.rs

@@ -0,0 +1,115 @@
+// Copyright 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/>.
+
+//! The PoA Bridge Pallet provides a way to include multiple instances of itself in a runtime. When
+//! synchronizing a Substrate chain which can include multiple instances of the bridge pallet we
+//! must somehow decide which of the instances to sync.
+//!
+//! Note that each instance of the bridge pallet is coupled with an instance of the currency exchange
+//! pallet. We must also have a way to create `Call`s for the correct currency exchange instance.
+//!
+//! This module helps by preparing the correct `Call`s for each of the different pallet instances.
+
+use crate::ethereum_types::QueuedEthereumHeader;
+use crate::substrate_types::{into_substrate_ethereum_header, into_substrate_ethereum_receipts};
+
+use bridge_node_runtime::exchange::EthereumTransactionInclusionProof as Proof;
+use bridge_node_runtime::Call;
+
+/// Interface for `Calls` which are needed to correctly sync the bridge.
+///
+/// Each instance of the bridge and currency exchange pallets in the bridge runtime requires similar
+/// but slightly different `Call` in order to be synchronized.
+pub trait BridgeInstance: Send + Sync + std::fmt::Debug {
+	/// Used to build a `Call` for importing signed headers to a Substrate runtime.
+	fn build_signed_header_call(&self, headers: Vec<QueuedEthereumHeader>) -> Call;
+	/// Used to build a `Call` for importing an unsigned header to a Substrate runtime.
+	fn build_unsigned_header_call(&self, header: QueuedEthereumHeader) -> Call;
+	/// Used to build a `Call` for importing peer transactions to a Substrate runtime.
+	fn build_currency_exchange_call(&self, proof: Proof) -> Call;
+}
+
+/// Corresponds to the Rialto instance used in the bridge runtime.
+#[derive(Default, Clone, Debug)]
+pub struct Rialto;
+
+impl BridgeInstance for Rialto {
+	fn build_signed_header_call(&self, headers: Vec<QueuedEthereumHeader>) -> Call {
+		let pallet_call = bridge_node_runtime::BridgeEthPoACall::import_signed_headers(
+			headers
+				.into_iter()
+				.map(|header| {
+					(
+						into_substrate_ethereum_header(header.header()),
+						into_substrate_ethereum_receipts(header.extra()),
+					)
+				})
+				.collect(),
+		);
+
+		bridge_node_runtime::Call::BridgeRialto(pallet_call)
+	}
+
+	fn build_unsigned_header_call(&self, header: QueuedEthereumHeader) -> Call {
+		let pallet_call = bridge_node_runtime::BridgeEthPoACall::import_unsigned_header(
+			into_substrate_ethereum_header(header.header()),
+			into_substrate_ethereum_receipts(header.extra()),
+		);
+
+		bridge_node_runtime::Call::BridgeRialto(pallet_call)
+	}
+
+	fn build_currency_exchange_call(&self, proof: Proof) -> Call {
+		let pallet_call = bridge_node_runtime::BridgeCurrencyExchangeCall::import_peer_transaction(proof);
+		bridge_node_runtime::Call::BridgeRialtoCurrencyExchange(pallet_call)
+	}
+}
+
+/// Corresponds to the Kovan instance used in the bridge runtime.
+#[derive(Default, Clone, Debug)]
+pub struct Kovan;
+
+impl BridgeInstance for Kovan {
+	fn build_signed_header_call(&self, headers: Vec<QueuedEthereumHeader>) -> Call {
+		let pallet_call = bridge_node_runtime::BridgeEthPoACall::import_signed_headers(
+			headers
+				.into_iter()
+				.map(|header| {
+					(
+						into_substrate_ethereum_header(header.header()),
+						into_substrate_ethereum_receipts(header.extra()),
+					)
+				})
+				.collect(),
+		);
+
+		bridge_node_runtime::Call::BridgeKovan(pallet_call)
+	}
+
+	fn build_unsigned_header_call(&self, header: QueuedEthereumHeader) -> Call {
+		let pallet_call = bridge_node_runtime::BridgeEthPoACall::import_unsigned_header(
+			into_substrate_ethereum_header(header.header()),
+			into_substrate_ethereum_receipts(header.extra()),
+		);
+
+		bridge_node_runtime::Call::BridgeKovan(pallet_call)
+	}
+
+	fn build_currency_exchange_call(&self, proof: Proof) -> Call {
+		let pallet_call = bridge_node_runtime::BridgeCurrencyExchangeCall::import_peer_transaction(proof);
+		bridge_node_runtime::Call::BridgeKovanCurrencyExchange(pallet_call)
+	}
+}

bridges/relays/ethereum/src/main.rs

@@ -26,6 +26,7 @@ mod exchange;
 mod exchange_loop;
 mod exchange_loop_metrics;
 mod headers;
+mod instances;
 mod metrics;
 mod rpc;
 mod rpc_errors;
@@ -40,12 +41,19 @@ mod sync_types;
 mod utils;
 
 use ethereum_client::{EthereumConnectionParams, EthereumSigningParams};
+use ethereum_deploy_contract::EthereumDeployContractParams;
+use ethereum_exchange::EthereumExchangeParams;
+use ethereum_exchange_submit::EthereumExchangeSubmitParams;
 use ethereum_sync_loop::EthereumSyncParams;
+use hex_literal::hex;
+use instances::{BridgeInstance, Kovan, Rialto};
 use parity_crypto::publickey::{KeyPair, Secret};
 use sp_core::crypto::Pair;
-use std::io::Write;
 use substrate_client::{SubstrateConnectionParams, SubstrateSigningParams};
 use substrate_sync_loop::SubstrateSyncParams;
+use sync::HeadersSyncParams;
+
+use std::io::Write;
 
 fn main() {
 	initialize();
@@ -210,110 +218,134 @@ fn substrate_signing_params(matches: &clap::ArgMatches) -> Result<SubstrateSigni
 }
 
 fn ethereum_sync_params(matches: &clap::ArgMatches) -> Result<EthereumSyncParams, String> {
-	let mut eth_sync_params = EthereumSyncParams::default();
-	eth_sync_params.eth = ethereum_connection_params(matches)?;
-	eth_sync_params.sub = substrate_connection_params(matches)?;
-	eth_sync_params.sub_sign = substrate_signing_params(matches)?;
-	eth_sync_params.metrics_params = metrics_params(matches)?;
+	let mut sync_params = HeadersSyncParams::ethereum_sync_default();
 
 	match matches.value_of("sub-tx-mode") {
-		Some("signed") => eth_sync_params.sync_params.target_tx_mode = sync::TargetTransactionMode::Signed,
+		Some("signed") => sync_params.target_tx_mode = sync::TargetTransactionMode::Signed,
 		Some("unsigned") => {
-			eth_sync_params.sync_params.target_tx_mode = sync::TargetTransactionMode::Unsigned;
+			sync_params.target_tx_mode = sync::TargetTransactionMode::Unsigned;
 
 			// tx pool won't accept too much unsigned transactions
-			eth_sync_params.sync_params.max_headers_in_submitted_status = 10;
+			sync_params.max_headers_in_submitted_status = 10;
 		}
-		Some("backup") => eth_sync_params.sync_params.target_tx_mode = sync::TargetTransactionMode::Backup,
+		Some("backup") => sync_params.target_tx_mode = sync::TargetTransactionMode::Backup,
 		Some(mode) => return Err(format!("Invalid sub-tx-mode: {}", mode)),
-		None => eth_sync_params.sync_params.target_tx_mode = sync::TargetTransactionMode::Signed,
+		None => sync_params.target_tx_mode = sync::TargetTransactionMode::Signed,
 	}
 
-	log::debug!(target: "bridge", "Ethereum sync params: {:?}", eth_sync_params);
+	let params = EthereumSyncParams {
+		eth_params: ethereum_connection_params(matches)?,
+		sub_params: substrate_connection_params(matches)?,
+		sub_sign: substrate_signing_params(matches)?,
+		metrics_params: metrics_params(matches)?,
+		instance: instance_params(matches)?,
+		sync_params,
+	};
 
-	Ok(eth_sync_params)
+	log::debug!(target: "bridge", "Ethereum sync params: {:?}", params);
+
+	Ok(params)
 }
 
 fn substrate_sync_params(matches: &clap::ArgMatches) -> Result<SubstrateSyncParams, String> {
-	let mut sub_sync_params = SubstrateSyncParams::default();
-	sub_sync_params.eth = ethereum_connection_params(matches)?;
-	sub_sync_params.eth_sign = ethereum_signing_params(matches)?;
-	sub_sync_params.sub = substrate_connection_params(matches)?;
-	sub_sync_params.metrics_params = metrics_params(matches)?;
-
-	if let Some(eth_contract) = matches.value_of("eth-contract") {
-		sub_sync_params.eth_contract_address = eth_contract.parse().map_err(|e| format!("{}", e))?;
-	}
-
-	log::debug!(target: "bridge", "Substrate sync params: {:?}", sub_sync_params);
-
-	Ok(sub_sync_params)
-}
-
-fn ethereum_deploy_contract_params(
-	matches: &clap::ArgMatches,
-) -> Result<ethereum_deploy_contract::EthereumDeployContractParams, String> {
-	let mut eth_deploy_params = ethereum_deploy_contract::EthereumDeployContractParams::default();
-	eth_deploy_params.eth = ethereum_connection_params(matches)?;
-	eth_deploy_params.eth_sign = ethereum_signing_params(matches)?;
-	eth_deploy_params.sub = substrate_connection_params(matches)?;
-
-	if let Some(eth_contract_code) = matches.value_of("eth-contract-code") {
-		eth_deploy_params.eth_contract_code =
-			hex::decode(&eth_contract_code).map_err(|e| format!("Failed to parse eth-contract-code: {}", e))?;
-	}
-
-	log::debug!(target: "bridge", "Deploy params: {:?}", eth_deploy_params);
-
-	Ok(eth_deploy_params)
-}
-
-fn ethereum_exchange_submit_params(
-	matches: &clap::ArgMatches,
-) -> Result<ethereum_exchange_submit::EthereumExchangeSubmitParams, String> {
-	let mut params = ethereum_exchange_submit::EthereumExchangeSubmitParams::default();
-	params.eth = ethereum_connection_params(matches)?;
-	params.eth_sign = ethereum_signing_params(matches)?;
-
-	if let Some(eth_nonce) = matches.value_of("eth-nonce") {
-		params.eth_nonce = Some(
-			ethereum_types::U256::from_dec_str(&eth_nonce).map_err(|e| format!("Failed to parse eth-nonce: {}", e))?,
-		);
-	}
-	if let Some(eth_amount) = matches.value_of("eth-amount") {
-		params.eth_amount = eth_amount
+	let eth_contract_address: ethereum_types::Address = if let Some(eth_contract) = matches.value_of("eth-contract") {
+		eth_contract.parse().map_err(|e| format!("{}", e))?
+	} else {
+		"731a10897d267e19b34503ad902d0a29173ba4b1"
 			.parse()
-			.map_err(|e| format!("Failed to parse eth-amount: {}", e))?;
-	}
-	if let Some(sub_recipient) = matches.value_of("sub-recipient") {
-		params.sub_recipient = hex::decode(&sub_recipient)
+			.expect("address is hardcoded, thus valid; qed")
+	};
+
+	let params = SubstrateSyncParams {
+		sub_params: substrate_connection_params(matches)?,
+		eth_params: ethereum_connection_params(matches)?,
+		eth_sign: ethereum_signing_params(matches)?,
+		metrics_params: metrics_params(matches)?,
+		instance: instance_params(matches)?,
+		sync_params: HeadersSyncParams::substrate_sync_default(),
+		eth_contract_address,
+	};
+
+	log::debug!(target: "bridge", "Substrate sync params: {:?}", params);
+
+	Ok(params)
+}
+
+fn ethereum_deploy_contract_params(matches: &clap::ArgMatches) -> Result<EthereumDeployContractParams, String> {
+	let eth_contract_code = if let Some(eth_contract_code) = matches.value_of("eth-contract-code") {
+		hex::decode(&eth_contract_code).map_err(|e| format!("Failed to parse eth-contract-code: {}", e))?
+	} else {
+		hex::decode(include_str!("../res/substrate-bridge-bytecode.hex")).expect("code is hardcoded, thus valid; qed")
+	};
+
+	let params = EthereumDeployContractParams {
+		eth_params: ethereum_connection_params(matches)?,
+		eth_sign: ethereum_signing_params(matches)?,
+		sub_params: substrate_connection_params(matches)?,
+		instance: instance_params(matches)?,
+		sub_initial_authorities_set_id: None,
+		sub_initial_authorities_set: None,
+		sub_initial_header: None,
+		eth_contract_code,
+	};
+
+	log::debug!(target: "bridge", "Deploy params: {:?}", params);
+
+	Ok(params)
+}
+
+fn ethereum_exchange_submit_params(matches: &clap::ArgMatches) -> Result<EthereumExchangeSubmitParams, String> {
+	let eth_nonce = if let Some(eth_nonce) = matches.value_of("eth-nonce") {
+		Some(ethereum_types::U256::from_dec_str(&eth_nonce).map_err(|e| format!("Failed to parse eth-nonce: {}", e))?)
+	} else {
+		None
+	};
+
+	let eth_amount = if let Some(eth_amount) = matches.value_of("eth-amount") {
+		eth_amount
+			.parse()
+			.map_err(|e| format!("Failed to parse eth-amount: {}", e))?
+	} else {
+		// This is in Wei, represents 1 ETH
+		1_000_000_000_000_000_000_u64.into()
+	};
+
+	// This is the well-known Substrate account of Ferdie
+	let default_recepient = hex!("1cbd2d43530a44705ad088af313e18f80b53ef16b36177cd4b77b846f2a5f07c");
+
+	let sub_recipient = if let Some(sub_recipient) = matches.value_of("sub-recipient") {
+		hex::decode(&sub_recipient)
 			.map_err(|err| err.to_string())
 			.and_then(|vsub_recipient| {
-				let expected_len = params.sub_recipient.len();
+				let expected_len = default_recepient.len();
 				if expected_len != vsub_recipient.len() {
 					Err(format!("invalid length. Expected {} bytes", expected_len))
 				} else {
-					let mut sub_recipient = params.sub_recipient;
+					let mut sub_recipient = default_recepient;
 					sub_recipient.copy_from_slice(&vsub_recipient[..expected_len]);
 					Ok(sub_recipient)
 				}
 			})
-			.map_err(|e| format!("Failed to parse sub-recipient: {}", e))?;
-	}
+			.map_err(|e| format!("Failed to parse sub-recipient: {}", e))?
+	} else {
+		default_recepient
+	};
+
+	let params = EthereumExchangeSubmitParams {
+		eth_params: ethereum_connection_params(matches)?,
+		eth_sign: ethereum_signing_params(matches)?,
+		eth_nonce,
+		eth_amount,
+		sub_recipient,
+	};
 
 	log::debug!(target: "bridge", "Submit Ethereum exchange tx params: {:?}", params);
 
 	Ok(params)
 }
 
-fn ethereum_exchange_params(matches: &clap::ArgMatches) -> Result<ethereum_exchange::EthereumExchangeParams, String> {
-	let mut params = ethereum_exchange::EthereumExchangeParams::default();
-	params.eth = ethereum_connection_params(matches)?;
-	params.sub = substrate_connection_params(matches)?;
-	params.sub_sign = substrate_signing_params(matches)?;
-	params.metrics_params = metrics_params(matches)?;
-
-	params.mode = match matches.value_of("eth-tx-hash") {
+fn ethereum_exchange_params(matches: &clap::ArgMatches) -> Result<EthereumExchangeParams, String> {
+	let mode = match matches.value_of("eth-tx-hash") {
 		Some(eth_tx_hash) => ethereum_exchange::ExchangeRelayMode::Single(
 			eth_tx_hash
 				.parse()
@@ -329,6 +361,15 @@ fn ethereum_exchange_params(matches: &clap::ArgMatches) -> Result<ethereum_excha
 		}),
 	};
 
+	let params = EthereumExchangeParams {
+		eth_params: ethereum_connection_params(matches)?,
+		sub_params: substrate_connection_params(matches)?,
+		sub_sign: substrate_signing_params(matches)?,
+		metrics_params: metrics_params(matches)?,
+		instance: instance_params(matches)?,
+		mode,
+	};
+
 	log::debug!(target: "bridge", "Ethereum exchange params: {:?}", params);
 
 	Ok(params)
@@ -352,3 +393,17 @@ fn metrics_params(matches: &clap::ArgMatches) -> Result<Option<metrics::MetricsP
 
 	Ok(Some(metrics_params))
 }
+
+fn instance_params(matches: &clap::ArgMatches) -> Result<Box<dyn BridgeInstance>, String> {
+	let instance: Box<dyn BridgeInstance> = if let Some(instance) = matches.value_of("sub-pallet-instance") {
+		match instance.to_lowercase().as_str() {
+			"rialto" => Box::new(Rialto::default()),
+			"kovan" => Box::new(Kovan::default()),
+			_ => return Err("Unsupported bridge pallet instance".to_string()),
+		}
+	} else {
+		unreachable!("CLI config enforces a default instance, can never be None")
+	};
+
+	Ok(instance)
+}

bridges/relays/ethereum/src/substrate_client.rs

@@ -15,12 +15,10 @@
 // along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
 
 use crate::ethereum_types::{Bytes, EthereumHeaderId, QueuedEthereumHeader, H256};
+use crate::instances::BridgeInstance;
 use crate::rpc::{Substrate, SubstrateRpc};
 use crate::rpc_errors::RpcError;
-use crate::substrate_types::{
-	into_substrate_ethereum_header, into_substrate_ethereum_receipts, Hash, Header as SubstrateHeader, Number,
-	SignedBlock as SignedSubstrateBlock,
-};
+use crate::substrate_types::{Hash, Header as SubstrateHeader, Number, SignedBlock as SignedSubstrateBlock};
 use crate::sync_types::{HeaderId, SubmittedHeaders};
 
 use async_trait::async_trait;
@@ -89,11 +87,13 @@ pub struct SubstrateRpcClient {
 	client: Client,
 	/// Genesis block hash.
 	genesis_hash: H256,
+	/// Instance of the bridge pallet being synchronized.
+	instance: Box<dyn BridgeInstance>,
 }
 
 impl SubstrateRpcClient {
 	/// Returns client that is able to call RPCs on Substrate node.
-	pub async fn new(params: SubstrateConnectionParams) -> Result<Self> {
+	pub async fn new(params: SubstrateConnectionParams, instance: Box<dyn BridgeInstance>) -> Result<Self> {
 		let uri = format!("http://{}:{}", params.host, params.port);
 		let transport = HttpTransportClient::new(&uri);
 		let raw_client = RawClient::new(transport);
@@ -102,7 +102,11 @@ impl SubstrateRpcClient {
 		let number: Number = Zero::zero();
 		let genesis_hash = Substrate::chain_get_block_hash(&client, number).await?;
 
-		Ok(Self { client, genesis_hash })
+		Ok(Self {
+			client,
+			genesis_hash,
+			instance,
+		})
 	}
 }
 
@@ -248,7 +252,8 @@ impl SubmitEthereumHeaders for SubstrateRpcClient {
 			let account_id = params.signer.public().as_array_ref().clone().into();
 			let nonce = self.next_account_index(account_id).await?;
 
-			let transaction = create_signed_submit_transaction(headers, &params.signer, nonce, self.genesis_hash);
+			let call = self.instance.build_signed_header_call(headers);
+			let transaction = create_signed_submit_transaction(call, &params.signer, nonce, self.genesis_hash);
 			let _ = self.submit_extrinsic(Bytes(transaction.encode())).await?;
 			Ok(())
 		}
@@ -276,9 +281,13 @@ impl SubmitEthereumHeaders for SubstrateRpcClient {
 	) -> SubmittedHeaders<EthereumHeaderId, RpcError> {
 		let mut ids = headers.iter().map(|header| header.id()).collect::<VecDeque<_>>();
 		let mut submitted_headers = SubmittedHeaders::default();
+
 		for header in headers {
 			let id = ids.pop_front().expect("both collections have same size; qed");
-			let transaction = create_unsigned_submit_transaction(header);
+
+			let call = self.instance.build_unsigned_header_call(header);
+			let transaction = create_unsigned_submit_transaction(call);
+
 			match self.submit_extrinsic(Bytes(transaction.encode())).await {
 				Ok(_) => submitted_headers.submitted.push(id),
 				Err(error) => {
@@ -335,15 +344,9 @@ impl SubmitEthereumExchangeTransactionProof for SubstrateRpcClient {
 		let account_id = params.signer.public().as_array_ref().clone().into();
 		let nonce = self.next_account_index(account_id).await?;
 
-		let transaction = create_signed_transaction(
-			// TODO [#209]: Change so that that it's dynamic
-			bridge_node_runtime::Call::BridgeRialtoCurrencyExchange(
-				bridge_node_runtime::BridgeCurrencyExchangeCall::import_peer_transaction(proof),
-			),
-			&params.signer,
-			nonce,
-			self.genesis_hash,
-		);
+		let call = self.instance.build_currency_exchange_call(proof);
+		let transaction = create_signed_transaction(call, &params.signer, nonce, self.genesis_hash);
+
 		let _ = self.submit_extrinsic(Bytes(transaction.encode())).await?;
 		Ok(())
 	}
@@ -351,40 +354,17 @@ impl SubmitEthereumExchangeTransactionProof for SubstrateRpcClient {
 
 /// Create signed Substrate transaction for submitting Ethereum headers.
 fn create_signed_submit_transaction(
-	headers: Vec<QueuedEthereumHeader>,
+	signed_call: bridge_node_runtime::Call,
 	signer: &sp_core::sr25519::Pair,
 	index: node_primitives::Index,
 	genesis_hash: H256,
 ) -> bridge_node_runtime::UncheckedExtrinsic {
-	create_signed_transaction(
-		// TODO [#209]: Change so that that it's dynamic
-		bridge_node_runtime::Call::BridgeRialto(bridge_node_runtime::BridgeEthPoACall::import_signed_headers(
-			headers
-				.into_iter()
-				.map(|header| {
-					(
-						into_substrate_ethereum_header(header.header()),
-						into_substrate_ethereum_receipts(header.extra()),
-					)
-				})
-				.collect(),
-		)),
-		signer,
-		index,
-		genesis_hash,
-	)
+	create_signed_transaction(signed_call, signer, index, genesis_hash)
 }
 
 /// Create unsigned Substrate transaction for submitting Ethereum header.
-fn create_unsigned_submit_transaction(header: QueuedEthereumHeader) -> bridge_node_runtime::UncheckedExtrinsic {
-	let function =
-		// TODO [#209]: Change so that that it's dynamic
-		bridge_node_runtime::Call::BridgeRialto(bridge_node_runtime::BridgeEthPoACall::import_unsigned_header(
-			into_substrate_ethereum_header(header.header()),
-			into_substrate_ethereum_receipts(header.extra()),
-		));
-
-	bridge_node_runtime::UncheckedExtrinsic::new_unsigned(function)
+fn create_unsigned_submit_transaction(call: bridge_node_runtime::Call) -> bridge_node_runtime::UncheckedExtrinsic {
+	bridge_node_runtime::UncheckedExtrinsic::new_unsigned(call)
 }
 
 /// Create signed Substrate transaction.

bridges/relays/ethereum/src/substrate_sync_loop.rs

@@ -20,6 +20,7 @@ use crate::ethereum_client::{
 	EthereumConnectionParams, EthereumHighLevelRpc, EthereumRpcClient, EthereumSigningParams,
 };
 use crate::ethereum_types::Address;
+use crate::instances::BridgeInstance;
 use crate::metrics::MetricsParams;
 use crate::rpc::SubstrateRpc;
 use crate::rpc_errors::RpcError;
@@ -27,66 +28,47 @@ use crate::substrate_client::{SubstrateConnectionParams, SubstrateRpcClient};
 use crate::substrate_types::{
 	GrandpaJustification, Hash, Header, Number, QueuedSubstrateHeader, SubstrateHeaderId, SubstrateHeadersSyncPipeline,
 };
-use crate::sync::{HeadersSyncParams, TargetTransactionMode};
+use crate::sync::HeadersSyncParams;
 use crate::sync_loop::{SourceClient, TargetClient};
 use crate::sync_types::{SourceHeader, SubmittedHeaders};
 
 use async_trait::async_trait;
 
+use std::fmt::Debug;
 use std::{collections::HashSet, time::Duration};
 
-/// Interval at which we check new Substrate headers when we are synced/almost synced.
-const SUBSTRATE_TICK_INTERVAL: Duration = Duration::from_secs(10);
-/// Interval at which we check new Ethereum blocks.
-const ETHEREUM_TICK_INTERVAL: Duration = Duration::from_secs(5);
-/// Max Ethereum headers we want to have in all 'before-submitted' states.
-const MAX_FUTURE_HEADERS_TO_DOWNLOAD: usize = 8;
-/// Max Ethereum headers count we want to have in 'submitted' state.
-const MAX_SUBMITTED_HEADERS: usize = 1;
-/// Max depth of in-memory headers in all states. Past this depth they will be forgotten (pruned).
-const PRUNE_DEPTH: u32 = 256;
+pub mod consts {
+	use super::*;
+
+	/// Interval at which we check new Substrate headers when we are synced/almost synced.
+	pub const SUBSTRATE_TICK_INTERVAL: Duration = Duration::from_secs(10);
+	/// Interval at which we check new Ethereum blocks.
+	pub const ETHEREUM_TICK_INTERVAL: Duration = Duration::from_secs(5);
+	/// Max Ethereum headers we want to have in all 'before-submitted' states.
+	pub const MAX_FUTURE_HEADERS_TO_DOWNLOAD: usize = 8;
+	/// Max Ethereum headers count we want to have in 'submitted' state.
+	pub const MAX_SUBMITTED_HEADERS: usize = 1;
+	/// Max depth of in-memory headers in all states. Past this depth they will be forgotten (pruned).
+	pub const PRUNE_DEPTH: u32 = 256;
+}
 
 /// Substrate synchronization parameters.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub struct SubstrateSyncParams {
+	/// Substrate connection params.
+	pub sub_params: SubstrateConnectionParams,
 	/// Ethereum connection params.
-	pub eth: EthereumConnectionParams,
+	pub eth_params: EthereumConnectionParams,
 	/// Ethereum signing params.
 	pub eth_sign: EthereumSigningParams,
 	/// Ethereum bridge contract address.
 	pub eth_contract_address: Address,
-	/// Substrate connection params.
-	pub sub: SubstrateConnectionParams,
 	/// Synchronization parameters.
 	pub sync_params: HeadersSyncParams,
 	/// Metrics parameters.
 	pub metrics_params: Option<MetricsParams>,
-}
-
-impl Default for SubstrateSyncParams {
-	fn default() -> Self {
-		SubstrateSyncParams {
-			eth: Default::default(),
-			eth_sign: Default::default(),
-			// the address 0x731a10897d267e19b34503ad902d0a29173ba4b1 is the address
-			// of the contract that is deployed by default signer and 0 nonce
-			eth_contract_address: "731a10897d267e19b34503ad902d0a29173ba4b1"
-				.parse()
-				.expect("address is hardcoded, thus valid; qed"),
-			sub: Default::default(),
-			sync_params: HeadersSyncParams {
-				max_future_headers_to_download: MAX_FUTURE_HEADERS_TO_DOWNLOAD,
-				max_headers_in_submitted_status: MAX_SUBMITTED_HEADERS,
-				// since we always have single Substrate header in separate Ethereum transaction,
-				// all max_**_in_single_submit aren't important here
-				max_headers_in_single_submit: 4,
-				max_headers_size_in_single_submit: std::usize::MAX,
-				prune_depth: PRUNE_DEPTH,
-				target_tx_mode: TargetTransactionMode::Signed,
-			},
-			metrics_params: Some(Default::default()),
-		}
-	}
+	/// Instance of the bridge pallet being synchronized.
+	pub instance: Box<dyn BridgeInstance>,
 }
 
 /// Substrate client as headers source.
@@ -199,21 +181,29 @@ impl TargetClient<SubstrateHeadersSyncPipeline> for EthereumHeadersTarget {
 
 /// Run Substrate headers synchronization.
 pub fn run(params: SubstrateSyncParams) -> Result<(), RpcError> {
-	let sub_params = params.clone();
+	let SubstrateSyncParams {
+		sub_params,
+		eth_params,
+		eth_sign,
+		eth_contract_address,
+		sync_params,
+		metrics_params,
+		instance,
+	} = params;
 
-	let eth_client = EthereumRpcClient::new(params.eth);
-	let sub_client = async_std::task::block_on(async { SubstrateRpcClient::new(sub_params.sub).await })?;
+	let eth_client = EthereumRpcClient::new(eth_params);
+	let sub_client = async_std::task::block_on(async { SubstrateRpcClient::new(sub_params, instance).await })?;
 
-	let target = EthereumHeadersTarget::new(eth_client, params.eth_contract_address, params.eth_sign);
+	let target = EthereumHeadersTarget::new(eth_client, eth_contract_address, eth_sign);
 	let source = SubstrateHeadersSource::new(sub_client);
 
 	crate::sync_loop::run(
 		source,
-		SUBSTRATE_TICK_INTERVAL,
+		consts::SUBSTRATE_TICK_INTERVAL,
 		target,
-		ETHEREUM_TICK_INTERVAL,
-		params.sync_params,
-		params.metrics_params,
+		consts::ETHEREUM_TICK_INTERVAL,
+		sync_params,
+		metrics_params,
 		futures::future::pending(),
 	);
 

bridges/relays/ethereum/src/sync.rs

@@ -36,6 +36,38 @@ pub struct HeadersSyncParams {
 	pub target_tx_mode: TargetTransactionMode,
 }
 
+impl HeadersSyncParams {
+	/// Default parameters for syncing Ethereum headers.
+	pub fn ethereum_sync_default() -> Self {
+		use crate::ethereum_sync_loop::consts::*;
+
+		Self {
+			max_future_headers_to_download: MAX_FUTURE_HEADERS_TO_DOWNLOAD,
+			max_headers_in_submitted_status: MAX_SUBMITTED_HEADERS,
+			max_headers_in_single_submit: MAX_HEADERS_IN_SINGLE_SUBMIT,
+			max_headers_size_in_single_submit: MAX_HEADERS_SIZE_IN_SINGLE_SUBMIT,
+			prune_depth: PRUNE_DEPTH,
+			target_tx_mode: TargetTransactionMode::Signed,
+		}
+	}
+
+	/// Default parameters for syncing Substrate headers.
+	pub fn substrate_sync_default() -> Self {
+		use crate::substrate_sync_loop::consts::*;
+
+		Self {
+			max_future_headers_to_download: MAX_FUTURE_HEADERS_TO_DOWNLOAD,
+			max_headers_in_submitted_status: MAX_SUBMITTED_HEADERS,
+			// since we always have single Substrate header in separate Ethereum transaction,
+			// all max_**_in_single_submit aren't important here
+			max_headers_in_single_submit: 4,
+			max_headers_size_in_single_submit: std::usize::MAX,
+			prune_depth: PRUNE_DEPTH,
+			target_tx_mode: TargetTransactionMode::Signed,
+		}
+	}
+}
+
 /// Target transaction mode.
 #[derive(Debug, PartialEq, Clone)]
 pub enum TargetTransactionMode {