Add cumulus-service (#187)

* Add cumulus-service

Crate that abstracts the service of a parachain.

* Make finalization infallible

cumulus/Cargo.lock

@@ -920,7 +920,6 @@ dependencies = [
  "polkadot-validation",
  "sc-cli",
  "sc-client-api",
- "sc-service",
  "sp-api",
  "sp-blockchain",
  "sp-consensus",
@@ -1093,6 +1092,27 @@ dependencies = [
  "trie-db",
 ]
 
+[[package]]
+name = "cumulus-service"
+version = "0.1.0"
+dependencies = [
+ "cumulus-collator",
+ "cumulus-consensus",
+ "cumulus-network",
+ "cumulus-primitives",
+ "polkadot-collator",
+ "polkadot-primitives",
+ "polkadot-service",
+ "sc-client-api",
+ "sc-service",
+ "sp-api",
+ "sp-blockchain",
+ "sp-consensus",
+ "sp-core",
+ "sp-inherents",
+ "sp-runtime",
+]
+
 [[package]]
 name = "cumulus-test-client"
 version = "0.1.0"
@@ -5788,6 +5808,7 @@ dependencies = [
  "cumulus-contracts-parachain-runtime",
  "cumulus-network",
  "cumulus-primitives",
+ "cumulus-service",
  "cumulus-test-parachain-runtime",
  "derive_more 0.15.0",
  "exit-future 0.1.4",

cumulus/Cargo.toml

@@ -11,6 +11,7 @@ members = [
 	"rococo-parachains/pallets/token-dealer",
 	"rococo-parachains/runtime",
 	"runtime",
+	"service",
 	"test/runtime",
 	"test/client",
 	"upward-message",

cumulus/collator/Cargo.toml

@@ -13,7 +13,6 @@ sp-consensus = { git = "https://github.com/paritytech/substrate", branch = "roco
 sp-inherents = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
 sp-api = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
 sc-client-api = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
-sc-service = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
 sc-cli = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
 
 # Polkadot dependencies

cumulus/collator/src/lib.rs

@@ -30,7 +30,6 @@ use cumulus_primitives::{
 use cumulus_runtime::ParachainBlockData;
 
 use sc_client_api::{BlockBackend, Finalizer, StateBackend, UsageProvider};
-use sc_service::Configuration;
 use sp_api::ApiExt;
 use sp_blockchain::HeaderBackend;
 use sp_consensus::{
@@ -547,16 +546,6 @@ where
 	}
 }
 
-/// Prepare the collator's node condifugration
-///
-/// This function will disable the default announcement of Substrate for the parachain in favor
-/// of the one of Cumulus.
-pub fn prepare_collator_config(mut parachain_config: Configuration) -> Configuration {
-	parachain_config.announce_block = false;
-
-	parachain_config
-}
-
 #[cfg(test)]
 mod tests {
 	use super::*;

cumulus/consensus/src/lib.rs

@@ -26,12 +26,10 @@ use sp_runtime::{
 	traits::{Block as BlockT, Header as HeaderT},
 };
 
-use polkadot_primitives::v0::{
+use polkadot_primitives::v0::{Block as PBlock, Hash as PHash, Id as ParaId, ParachainHost};
-	Id as ParaId, ParachainHost, Block as PBlock, Hash as PHash,
-};
 
 use codec::Decode;
-use futures::{future, Future, FutureExt, Stream, StreamExt, TryFutureExt, TryStreamExt};
+use futures::{future, Future, FutureExt, Stream, StreamExt};
 use log::{error, trace, warn};
 
 use std::{marker::PhantomData, sync::Arc};
@@ -118,26 +116,39 @@ where
 
 		polkadot
 			.finalized_heads(para_id)?
-			.map(|head_data| {
+			.filter_map(|head_data| {
-				<<Block as BlockT>::Header>::decode(&mut &head_data[..])
+				let res = match <<Block as BlockT>::Header>::decode(&mut &head_data[..]) {
-					.map_err(|_| Error::InvalidHeadData)
+					Ok(header) => Some(header),
-			})
+					Err(err) => {
-			.try_for_each(move |p_head| {
-				future::ready(
-					finalize_block(&*local, p_head.hash())
-						.map_err(Error::Client)
-						.map(|_| ()),
-				)
-			})
-			.map_err(|e| {
 						warn!(
 							target: "cumulus-consensus",
-				"Failed to finalize block: {:?}", e)
+							"Could not decode Parachain header for finalizing: {:?}",
-			})
+							err,
-			.map(|_| ())
+						);
+						None
+					}
 				};
 
-	Ok(future::select(follow_finalized, follow_new_best(para_id, local, polkadot, announce_block)?).map(|_| ()))
+				future::ready(res)
+			})
+			.for_each(move |p_head| {
+				if let Err(e) = finalize_block(&*local, p_head.hash()) {
+					warn!(
+						target: "cumulus-consensus",
+						"Failed to finalize block: {:?}",
+						e,
+					);
+				}
+
+				future::ready(())
+			})
+	};
+
+	Ok(future::select(
+		follow_finalized,
+		follow_new_best(para_id, local, polkadot, announce_block)?,
+	)
+	.map(|_| ()))
 }
 
 /// Follow the relay chain new best head, to update the Parachain new best head.

cumulus/rococo-parachains/Cargo.toml

@@ -57,6 +57,7 @@ cumulus-consensus = { path = "../consensus" }
 cumulus-collator = { path = "../collator" }
 cumulus-network = { path = "../network" }
 cumulus-primitives = { path = "../primitives" }
+cumulus-service = { path = "../service" }
 
 # Polkadot dependencies
 polkadot-primitives = { git = "https://github.com/paritytech/polkadot", branch = "rococo-branch" }

cumulus/rococo-parachains/src/command.rs

@@ -256,7 +256,7 @@ pub fn run() -> Result<()> {
 					if cli.run.base.validator { "yes" } else { "no" }
 				);
 
-				crate::service::run_collator(
+				crate::service::run_node(
 					config,
 					key,
 					polkadot_config,

cumulus/rococo-parachains/src/integration_test.rs

@@ -105,7 +105,7 @@ async fn integration_test() {
 		let parachain_config =
 			parachain_config(task_executor.clone(), Charlie, vec![], para_id).unwrap();
 		let (_service, charlie_client) =
-			crate::service::run_collator(parachain_config, key, polkadot_config, para_id, true)
+			crate::service::run_node(parachain_config, key, polkadot_config, para_id, true)
 				.unwrap();
 		sleep(Duration::from_secs(3)).await;
 		charlie_client.wait_for_blocks(4).await;

cumulus/rococo-parachains/src/service.rs

@@ -15,19 +15,18 @@
 // along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
 
 use ansi_term::Color;
-use cumulus_collator::{prepare_collator_config, CollatorBuilder};
+use cumulus_network::DelayedBlockAnnounceValidator;
-use cumulus_network::{DelayedBlockAnnounceValidator, JustifiedBlockAnnounceValidator};
+use cumulus_service::{
-use polkadot_primitives::v0::{CollatorPair, Block as PBlock, Id as ParaId};
+	prepare_node_config, start_collator, start_full_node, StartCollatorParams, StartFullNodeParams,
+};
+use polkadot_primitives::v0::CollatorPair;
 use sc_executor::native_executor_instance;
 pub use sc_executor::NativeExecutor;
 use sc_informant::OutputFormat;
-use sc_service::{Configuration, PartialComponents, TaskManager, TFullBackend, TFullClient, Role};
+use sc_service::{Configuration, PartialComponents, Role, TFullBackend, TFullClient, TaskManager};
-use std::sync::Arc;
+use sp_runtime::traits::BlakeTwo256;
-use sp_core::crypto::Pair;
 use sp_trie::PrefixedMemoryDB;
-use sp_runtime::traits::{BlakeTwo256, Block as BlockT};
+use std::sync::Arc;
-use polkadot_service::{AbstractClient, RuntimeApiCollection};
-use sp_consensus::SyncOracle;
 
 // Our native executor instance.
 native_executor_instance!(
@@ -40,22 +39,36 @@ native_executor_instance!(
 ///
 /// Use this macro if you don't actually need the full service, but just the builder in order to
 /// be able to perform chain operations.
-pub fn new_partial(config: &mut Configuration) -> Result<
+pub fn new_partial(
+	config: &mut Configuration,
+) -> Result<
 	PartialComponents<
-		TFullClient<parachain_runtime::opaque::Block, parachain_runtime::RuntimeApi, crate::service::Executor>,
+		TFullClient<
+			parachain_runtime::opaque::Block,
+			parachain_runtime::RuntimeApi,
+			crate::service::Executor,
+		>,
 		TFullBackend<parachain_runtime::opaque::Block>,
 		(),
-		sp_consensus::import_queue::BasicQueue<parachain_runtime::opaque::Block, PrefixedMemoryDB<BlakeTwo256>>,
+		sp_consensus::import_queue::BasicQueue<
-		sc_transaction_pool::FullPool<parachain_runtime::opaque::Block, TFullClient<parachain_runtime::opaque::Block, parachain_runtime::RuntimeApi, crate::service::Executor>>,
+			parachain_runtime::opaque::Block,
+			PrefixedMemoryDB<BlakeTwo256>,
+		>,
+		sc_transaction_pool::FullPool<
+			parachain_runtime::opaque::Block,
+			TFullClient<
+				parachain_runtime::opaque::Block,
+				parachain_runtime::RuntimeApi,
+				crate::service::Executor,
+			>,
+		>,
 		(),
 	>,
 	sc_service::Error,
->
+> {
-{
 	let inherent_data_providers = sp_inherents::InherentDataProviders::new();
 
-	let (client, backend, keystore, task_manager) =
+	let (client, backend, keystore, task_manager) = sc_service::new_full_parts::<
-		sc_service::new_full_parts::<
 		parachain_runtime::opaque::Block,
 		parachain_runtime::RuntimeApi,
 		crate::service::Executor,
@@ -96,24 +109,30 @@ pub fn new_partial(config: &mut Configuration) -> Result<
 	Ok(params)
 }
 
-/// Run a collator node with the given parachain `Configuration` and relaychain `Configuration`
+/// Run a node with the given parachain `Configuration` and relay chain `Configuration`
 ///
 /// This function blocks until done.
-pub fn run_collator(
+pub fn run_node(
 	parachain_config: Configuration,
-	key: Arc<CollatorPair>,
+	collator_key: Arc<CollatorPair>,
 	mut polkadot_config: polkadot_collator::Configuration,
 	id: polkadot_primitives::v0::Id,
 	validator: bool,
 ) -> sc_service::error::Result<(
 	TaskManager,
-	Arc<TFullClient<parachain_runtime::opaque::Block, parachain_runtime::RuntimeApi, crate::service::Executor>>,
+	Arc<
+		TFullClient<
+			parachain_runtime::opaque::Block,
+			parachain_runtime::RuntimeApi,
+			crate::service::Executor,
+		>,
+	>,
 )> {
 	if matches!(parachain_config.role, Role::Light) {
 		return Err("Light client not supported!".into());
 	}
 
-	let mut parachain_config = prepare_collator_config(parachain_config);
+	let mut parachain_config = prepare_node_config(parachain_config);
 
 	parachain_config.informant_output_format = OutputFormat {
 		enable_color: true,
@@ -125,7 +144,8 @@ pub fn run_collator(
 	};
 
 	let params = new_partial(&mut parachain_config)?;
-	params.inherent_data_providers
+	params
+		.inherent_data_providers
 		.register_provider(sp_timestamp::InherentDataProvider)
 		.unwrap();
 
@@ -171,7 +191,7 @@ pub fn run_collator(
 		})
 	};
 
-	let _rpc_handlers = sc_service::spawn_tasks(sc_service::SpawnTasksParams {
+	sc_service::spawn_tasks(sc_service::SpawnTasksParams {
 		on_demand: None,
 		remote_blockchain: None,
 		rpc_extensions_builder,
@@ -187,6 +207,8 @@ pub fn run_collator(
 		system_rpc_tx,
 	})?;
 
+	let announce_block = Arc::new(move |hash, data| network.announce_block(hash, data));
+
 	if validator {
 		let proposer_factory = sc_basic_authorship::ProposerFactory::new(
 			client.clone(),
@@ -194,76 +216,36 @@ pub fn run_collator(
 			prometheus_registry.as_ref(),
 		);
 
-		let block_import = client.clone();
+		let params = StartCollatorParams {
-		let announce_block = Arc::new(move |hash, data| network.announce_block(hash, data));
-		let builder = CollatorBuilder::new(
-			proposer_factory,
-			params.inherent_data_providers,
-			block_import,
-			client.clone(),
-			id,
-			client.clone(),
-			announce_block,
-			block_announce_validator,
-		);
-
-		let (polkadot_future, polkadot_task_manager) =
-			polkadot_collator::start_collator(builder, id, key, polkadot_config)?;
-
-		task_manager
-			.spawn_essential_handle()
-			.spawn("polkadot", polkadot_future);
-
-		task_manager.add_child(polkadot_task_manager);
-	} else {
-		let is_light = matches!(polkadot_config.role, Role::Light);
-		let (polkadot_task_manager, client, handles) = if is_light {
-			Err("Light client not supported.".into())
-		} else {
-			polkadot_service::build_full(
-				polkadot_config,
-				Some((key.public(), id)),
-				None,
-				false,
-				6000,
-				None,
-			)
-		}?;
-		let polkadot_network = handles.polkadot_network.expect("polkadot service is started; qed");
-		client.execute_with(SetDelayedBlockAnnounceValidator {
-			block_announce_validator,
 			para_id: id,
-			polkadot_sync_oracle: Box::new(polkadot_network),
+			block_import: client.clone(),
-		});
+			proposer_factory,
+			inherent_data_providers: params.inherent_data_providers,
+			block_status: client.clone(),
+			announce_block,
+			client: client.clone(),
+			block_announce_validator,
+			task_manager: &mut task_manager,
+			polkadot_config,
+			collator_key,
+		};
 
-		task_manager.add_child(polkadot_task_manager);
+		start_collator(params)?;
+	} else {
+		let params = StartFullNodeParams {
+			client: client.clone(),
+			announce_block,
+			polkadot_config,
+			collator_key,
+			block_announce_validator,
+			task_manager: &mut task_manager,
+			para_id: id,
+		};
+
+		start_full_node(params)?;
 	}
 
 	start_network.start_network();
 
 	Ok((task_manager, client))
 }
-
-struct SetDelayedBlockAnnounceValidator<B: BlockT> {
-	block_announce_validator: DelayedBlockAnnounceValidator<B>,
-	para_id: ParaId,
-	polkadot_sync_oracle: Box<dyn SyncOracle + Send>,
-}
-
-impl<B: BlockT> polkadot_service::ExecuteWithClient for SetDelayedBlockAnnounceValidator<B> {
-	type Output = ();
-
-	fn execute_with_client<Client, Api, Backend>(self, client: Arc<Client>) -> Self::Output
-		where<Api as sp_api::ApiExt<PBlock>>::StateBackend: sp_api::StateBackend<BlakeTwo256>,
-		Backend: sc_client_api::Backend<PBlock>,
-		Backend::State: sp_api::StateBackend<BlakeTwo256>,
-		Api: RuntimeApiCollection<StateBackend = Backend::State>,
-		Client: AbstractClient<PBlock, Backend, Api = Api> + 'static
-	{
-		self.block_announce_validator.set(Box::new(JustifiedBlockAnnounceValidator::new(
-			client,
-			self.para_id,
-			self.polkadot_sync_oracle,
-		)));
-	}
-}

cumulus/service/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "cumulus-service"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+# Cumulus dependencies
+cumulus-consensus = { path = "../consensus" }
+cumulus-collator = { path = "../collator" }
+cumulus-primitives = { path = "../primitives" }
+cumulus-network = { path = "../network" }
+
+# Substrate dependencies
+sc-service = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sc-client-api = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sp-consensus = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sp-api = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sp-core = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sp-inherents = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+sp-blockchain = { git = "https://github.com/paritytech/substrate", branch = "rococo-branch" }
+
+# Polkadot dependencies
+polkadot-collator = { git = "https://github.com/paritytech/polkadot", branch = "rococo-branch" }
+polkadot-primitives = { git = "https://github.com/paritytech/polkadot", branch = "rococo-branch" }
+polkadot-service = { git = "https://github.com/paritytech/polkadot", branch = "rococo-branch" }

cumulus/service/src/lib.rs

@@ -0,0 +1,246 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Cumulus.
+
+// Substrate 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.
+
+// Substrate 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 Cumulus.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Cumulus service
+//!
+//! Provides functions for starting a collator node or a normal full node.
+
+use cumulus_collator::CollatorBuilder;
+use cumulus_network::{DelayedBlockAnnounceValidator, JustifiedBlockAnnounceValidator};
+use cumulus_primitives::ParaId;
+use polkadot_primitives::v0::{Block as PBlock, CollatorPair};
+use polkadot_service::{AbstractClient, RuntimeApiCollection};
+use sc_client_api::{Backend as BackendT, BlockBackend, Finalizer, UsageProvider};
+use sc_service::{Configuration, Role, TaskManager};
+use sp_blockchain::{HeaderBackend, Result as ClientResult};
+use sp_consensus::{BlockImport, Environment, Error as ConsensusError, Proposer, SyncOracle};
+use sp_core::crypto::Pair;
+use sp_inherents::InherentDataProviders;
+use sp_runtime::traits::{BlakeTwo256, Block as BlockT};
+use std::{marker::PhantomData, sync::Arc};
+
+/// Parameters given to [`start_collator`].
+pub struct StartCollatorParams<'a, Block: BlockT, PF, BI, BS, Client> {
+	pub para_id: ParaId,
+	pub proposer_factory: PF,
+	pub inherent_data_providers: InherentDataProviders,
+	pub block_import: BI,
+	pub block_status: Arc<BS>,
+	pub announce_block: Arc<dyn Fn(Block::Hash, Vec<u8>) + Send + Sync>,
+	pub client: Arc<Client>,
+	pub block_announce_validator: DelayedBlockAnnounceValidator<Block>,
+	pub task_manager: &'a mut TaskManager,
+	pub polkadot_config: Configuration,
+	pub collator_key: Arc<CollatorPair>,
+}
+
+/// Start a collator node for a parachain.
+///
+/// A collator is similar to a validator in a normal blockchain.
+/// It is reponsible for producing blocks and sending the blocks to a
+/// parachain validator for validation and inclusion into the relay chain.
+pub fn start_collator<'a, Block, PF, BI, BS, Client, Backend>(
+	StartCollatorParams {
+		para_id,
+		proposer_factory,
+		inherent_data_providers,
+		block_import,
+		block_status,
+		announce_block,
+		client,
+		block_announce_validator,
+		task_manager,
+		polkadot_config,
+		collator_key,
+	}: StartCollatorParams<'a, Block, PF, BI, BS, Client>,
+) -> sc_service::error::Result<()>
+where
+	Block: BlockT,
+	PF: Environment<Block> + Send + 'static,
+	BI: BlockImport<
+			Block,
+			Error = ConsensusError,
+			Transaction = <PF::Proposer as Proposer<Block>>::Transaction,
+		> + Send
+		+ Sync
+		+ 'static,
+	BS: BlockBackend<Block> + Send + Sync + 'static,
+	Client: Finalizer<Block, Backend>
+		+ UsageProvider<Block>
+		+ HeaderBackend<Block>
+		+ Send
+		+ Sync
+		+ BlockBackend<Block>
+		+ 'static,
+	for<'b> &'b Client: BlockImport<Block>,
+	Backend: BackendT<Block> + 'static,
+{
+	let builder = CollatorBuilder::new(
+		proposer_factory,
+		inherent_data_providers,
+		block_import,
+		block_status,
+		para_id,
+		client,
+		announce_block,
+		block_announce_validator,
+	);
+
+	let (polkadot_future, polkadot_task_manager) =
+		polkadot_collator::start_collator(builder, para_id, collator_key, polkadot_config)?;
+
+	task_manager
+		.spawn_essential_handle()
+		.spawn("polkadot", polkadot_future);
+
+	task_manager.add_child(polkadot_task_manager);
+
+	Ok(())
+}
+
+/// Parameters given to [`start_full_node`].
+pub struct StartFullNodeParams<'a, Block: BlockT, Client> {
+	pub polkadot_config: Configuration,
+	pub collator_key: Arc<CollatorPair>,
+	pub para_id: ParaId,
+	pub block_announce_validator: DelayedBlockAnnounceValidator<Block>,
+	pub client: Arc<Client>,
+	pub announce_block: Arc<dyn Fn(Block::Hash, Vec<u8>) + Send + Sync>,
+	pub task_manager: &'a mut TaskManager,
+}
+
+/// Start a full node for a parachain.
+///
+/// A full node will only sync the given parachain and will follow the
+/// tip of the chain.
+pub fn start_full_node<Block, Client, Backend>(
+	StartFullNodeParams {
+		polkadot_config,
+		collator_key,
+		para_id,
+		block_announce_validator,
+		client,
+		announce_block,
+		task_manager,
+	}: StartFullNodeParams<Block, Client>,
+) -> sc_service::error::Result<()>
+where
+	Block: BlockT,
+	Client: Finalizer<Block, Backend>
+		+ UsageProvider<Block>
+		+ Send
+		+ Sync
+		+ BlockBackend<Block>
+		+ 'static,
+	for<'a> &'a Client: BlockImport<Block>,
+	Backend: BackendT<Block> + 'static,
+{
+	let is_light = matches!(polkadot_config.role, Role::Light);
+	let (polkadot_task_manager, pclient, handles) = if is_light {
+		Err("Light client not supported.".into())
+	} else {
+		polkadot_service::build_full(
+			polkadot_config,
+			Some((collator_key.public(), para_id)),
+			None,
+			false,
+			6000,
+			None,
+		)
+	}?;
+
+	let polkadot_network = handles
+		.polkadot_network
+		.expect("Polkadot service is started; qed");
+
+	pclient.execute_with(InitParachainFullNode {
+		block_announce_validator,
+		para_id,
+		polkadot_sync_oracle: Box::new(polkadot_network),
+		announce_block,
+		client,
+		task_manager,
+		_phantom: PhantomData,
+	})?;
+
+	task_manager.add_child(polkadot_task_manager);
+
+	Ok(())
+}
+
+/// Prepare the parachain's node condifugration
+///
+/// This function will disable the default announcement of Substrate for the parachain in favor
+/// of the one of Cumulus.
+pub fn prepare_node_config(mut parachain_config: Configuration) -> Configuration {
+	parachain_config.announce_block = false;
+
+	parachain_config
+}
+
+struct InitParachainFullNode<'a, Block: BlockT, Client, Backend> {
+	block_announce_validator: DelayedBlockAnnounceValidator<Block>,
+	para_id: ParaId,
+	polkadot_sync_oracle: Box<dyn SyncOracle + Send>,
+	announce_block: Arc<dyn Fn(Block::Hash, Vec<u8>) + Send + Sync>,
+	client: Arc<Client>,
+	task_manager: &'a mut TaskManager,
+	_phantom: PhantomData<Backend>,
+}
+
+impl<'a, Block, Client, Backend> polkadot_service::ExecuteWithClient
+	for InitParachainFullNode<'a, Block, Client, Backend>
+where
+	Block: BlockT,
+	Client: Finalizer<Block, Backend>
+		+ UsageProvider<Block>
+		+ Send
+		+ Sync
+		+ BlockBackend<Block>
+		+ 'static,
+	for<'b> &'b Client: BlockImport<Block>,
+	Backend: BackendT<Block> + 'static,
+{
+	type Output = ClientResult<()>;
+
+	fn execute_with_client<PClient, Api, PBackend>(self, client: Arc<PClient>) -> Self::Output
+	where
+		<Api as sp_api::ApiExt<PBlock>>::StateBackend: sp_api::StateBackend<BlakeTwo256>,
+		PBackend: sc_client_api::Backend<PBlock>,
+		PBackend::State: sp_api::StateBackend<BlakeTwo256>,
+		Api: RuntimeApiCollection<StateBackend = PBackend::State>,
+		PClient: AbstractClient<PBlock, PBackend, Api = Api> + 'static,
+	{
+		self.block_announce_validator
+			.set(Box::new(JustifiedBlockAnnounceValidator::new(
+				client.clone(),
+				self.para_id,
+				self.polkadot_sync_oracle,
+			)));
+
+		let future = cumulus_consensus::follow_polkadot(
+			self.para_id,
+			self.client,
+			client,
+			self.announce_block,
+		)?;
+		self.task_manager
+			.spawn_essential_handle()
+			.spawn("cumulus-consensus", future);
+
+		Ok(())
+	}
+}