Various small improvements to service construction. (#6738)

* Remove service components and add build_network, build_offchain_workers etc

* Improve transaction pool api

* Remove commented out line

* Add PartialComponents

* Add BuildNetworkParams, documentation

* Remove unused imports in tests

* Apply suggestions from code review

Co-authored-by: Nikolay Volf <nikvolf@gmail.com>

* Remove unused imports in node-bench

Co-authored-by: Nikolay Volf <nikvolf@gmail.com>

substrate/Cargo.lock

@@ -7039,6 +7039,7 @@ dependencies = [
  "sp-core",
  "sp-externalities",
  "sp-finality-grandpa",
+ "sp-inherents",
  "sp-io",
  "sp-runtime",
  "sp-session",

substrate/bin/node-template/node/src/command.rs

@@ -19,8 +19,8 @@ use crate::chain_spec;
 use crate::cli::Cli;
 use crate::service;
 use sc_cli::{SubstrateCli, RuntimeVersion, Role, ChainSpec};
-use sc_service::ServiceParams;
-use crate::service::new_full_params;
+use sc_service::PartialComponents;
+use crate::service::new_partial;
 
 impl SubstrateCli for Cli {
 	fn impl_name() -> String {
@@ -70,8 +70,8 @@ pub fn run() -> sc_cli::Result<()> {
 		Some(subcommand) => {
 			let runner = cli.create_runner(subcommand)?;
 			runner.run_subcommand(subcommand, |config| {
-				let (ServiceParams { client, backend, task_manager, import_queue, .. }, ..)
-					= new_full_params(config)?;
+				let PartialComponents { client, backend, task_manager, import_queue, .. }
+					= new_partial(&config)?;
 				Ok((client, backend, import_queue, task_manager))
 			})
 		}

substrate/bin/node-template/node/src/service.rs

@@ -4,14 +4,12 @@ use std::sync::Arc;
 use std::time::Duration;
 use sc_client_api::{ExecutorProvider, RemoteBackend};
 use node_template_runtime::{self, opaque::Block, RuntimeApi};
-use sc_service::{error::Error as ServiceError, Configuration, ServiceComponents, TaskManager};
+use sc_service::{error::Error as ServiceError, Configuration, TaskManager};
 use sp_inherents::InherentDataProviders;
 use sc_executor::native_executor_instance;
 pub use sc_executor::NativeExecutor;
 use sp_consensus_aura::sr25519::{AuthorityPair as AuraPair};
-use sc_finality_grandpa::{
-	FinalityProofProvider as GrandpaFinalityProofProvider, StorageAndProofProvider, SharedVoterState,
-};
+use sc_finality_grandpa::{FinalityProofProvider as GrandpaFinalityProofProvider, SharedVoterState};
 
 // Our native executor instance.
 native_executor_instance!(
@@ -24,18 +22,15 @@ type FullClient = sc_service::TFullClient<Block, RuntimeApi, Executor>;
 type FullBackend = sc_service::TFullBackend<Block>;
 type FullSelectChain = sc_consensus::LongestChain<FullBackend, Block>;
 
-pub fn new_full_params(config: Configuration) -> Result<(
-	sc_service::ServiceParams<
-		Block, FullClient,
-		sc_consensus_aura::AuraImportQueue<Block, FullClient>,
-		sc_transaction_pool::FullPool<Block, FullClient>,
-		(), FullBackend,
-	>,
-	FullSelectChain,
-	sp_inherents::InherentDataProviders,
-	sc_finality_grandpa::GrandpaBlockImport<FullBackend, Block, FullClient, FullSelectChain>,
-	sc_finality_grandpa::LinkHalf<Block, FullClient, FullSelectChain>
-), ServiceError> {
+pub fn new_partial(config: &Configuration) -> Result<sc_service::PartialComponents<
+	FullClient, FullBackend, FullSelectChain,
+	sc_consensus_aura::AuraImportQueue<Block, FullClient>,
+	sc_transaction_pool::FullPool<Block, FullClient>,
+	(
+		sc_finality_grandpa::GrandpaBlockImport<FullBackend, Block, FullClient, FullSelectChain>,
+		sc_finality_grandpa::LinkHalf<Block, FullClient, FullSelectChain>
+	)
+>, ServiceError> {
 	let inherent_data_providers = sp_inherents::InherentDataProviders::new();
 
 	let (client, backend, keystore, task_manager) =
@@ -44,12 +39,8 @@ pub fn new_full_params(config: Configuration) -> Result<(
 
 	let select_chain = sc_consensus::LongestChain::new(backend.clone());
 
-	let pool_api = sc_transaction_pool::FullChainApi::new(
-		client.clone(), config.prometheus_registry(),
-	);
 	let transaction_pool = sc_transaction_pool::BasicPool::new_full(
 		config.transaction_pool.clone(),
-		std::sync::Arc::new(pool_api),
 		config.prometheus_registry(),
 		task_manager.spawn_handle(),
 		client.clone(),
@@ -74,56 +65,62 @@ pub fn new_full_params(config: Configuration) -> Result<(
 		config.prometheus_registry(),
 	)?;
 
-	let provider = client.clone() as Arc<dyn StorageAndProofProvider<_, _>>;
-	let finality_proof_provider =
-		Arc::new(GrandpaFinalityProofProvider::new(backend.clone(), provider));
-	
-	let params = sc_service::ServiceParams {
-		backend, client, import_queue, keystore, task_manager, transaction_pool,
-		config,
-		block_announce_validator_builder: None,
-		finality_proof_request_builder: None,
-		finality_proof_provider: Some(finality_proof_provider),
-		on_demand: None,
-		remote_blockchain: None,
-		rpc_extensions_builder: Box::new(|_| ()),
-	};
-
-	Ok((
-		params, select_chain, inherent_data_providers,
-		grandpa_block_import, grandpa_link,
-	))
+	Ok(sc_service::PartialComponents {
+		client, backend, task_manager, import_queue, keystore, select_chain, transaction_pool,
+		inherent_data_providers,
+		other: (grandpa_block_import, grandpa_link),
+	})
 }
 
 /// Builds a new service for a full client.
 pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {	
-	let (
-		params, select_chain, inherent_data_providers,
-		block_import, grandpa_link,
-	) = new_full_params(config)?;
+	let sc_service::PartialComponents {
+		client, backend, mut task_manager, import_queue, keystore, select_chain, transaction_pool,
+		inherent_data_providers,
+		other: (block_import, grandpa_link),
+	} = new_partial(&config)?;
 
-	let (
-		role, force_authoring, name, enable_grandpa, prometheus_registry,
-		client, transaction_pool, keystore,
-	) = {
-		let sc_service::ServiceParams {
-			config, client, transaction_pool, keystore, ..
-		} = &params;
+	let finality_proof_provider =
+		GrandpaFinalityProofProvider::new_for_service(backend.clone(), client.clone());
 
-		(
-			config.role.clone(),
-			config.force_authoring,
-			config.network.node_name.clone(),
-			!config.disable_grandpa,
-			config.prometheus_registry().cloned(),
+	let (network, network_status_sinks, system_rpc_tx) =
+		sc_service::build_network(sc_service::BuildNetworkParams {
+			config: &config,
+			client: client.clone(),
+			transaction_pool: transaction_pool.clone(),
+			spawn_handle: task_manager.spawn_handle(),
+			import_queue,
+			on_demand: None,
+			block_announce_validator_builder: None,
+			finality_proof_request_builder: None,
+			finality_proof_provider: Some(finality_proof_provider.clone()), 
+		})?;
 
-			client.clone(), transaction_pool.clone(), keystore.clone(),
-		)
-	};
+	if config.offchain_worker.enabled {
+		sc_service::build_offchain_workers(
+			&config, backend.clone(), task_manager.spawn_handle(), client.clone(), network.clone(),
+		);
+	}
 
-	let ServiceComponents {
-		task_manager, network, telemetry_on_connect_sinks, ..
-	 } = sc_service::build(params)?;
+	let role = config.role.clone();
+	let force_authoring = config.force_authoring;
+	let name = config.network.node_name.clone();
+	let enable_grandpa = !config.disable_grandpa;
+	let prometheus_registry = config.prometheus_registry().cloned();
+	let telemetry_connection_sinks = sc_service::TelemetryConnectionSinks::default();
+
+	sc_service::spawn_tasks(sc_service::SpawnTasksParams {
+		network: network.clone(),
+		client: client.clone(),
+		keystore: keystore.clone(),
+		task_manager: &mut task_manager,
+		transaction_pool: transaction_pool.clone(),
+		telemetry_connection_sinks: telemetry_connection_sinks.clone(),
+		rpc_extensions_builder: Box::new(|_| ()),
+		on_demand: None,
+		remote_blockchain: None,
+		backend, network_status_sinks, system_rpc_tx, config,
+	})?;
 
 	if role.is_authority() {
 		let proposer = sc_basic_authorship::ProposerFactory::new(
@@ -183,7 +180,7 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 			link: grandpa_link,
 			network,
 			inherent_data_providers,
-			telemetry_on_connect: Some(telemetry_on_connect_sinks.on_connect_stream()),
+			telemetry_on_connect: Some(telemetry_connection_sinks.on_connect_stream()),
 			voting_rule: sc_finality_grandpa::VotingRulesBuilder::default().build(),
 			prometheus_registry,
 			shared_voter_state: SharedVoterState::empty(),
@@ -208,18 +205,16 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 
 /// Builds a new service for a light client.
 pub fn new_light(config: Configuration) -> Result<TaskManager, ServiceError> {
-	let (client, backend, keystore, task_manager, on_demand) =
+	let (client, backend, keystore, mut task_manager, on_demand) =
 		sc_service::new_light_parts::<Block, RuntimeApi, Executor>(&config)?;
-	
-	let transaction_pool_api = Arc::new(sc_transaction_pool::LightChainApi::new(
-		client.clone(), on_demand.clone(),
-	));
-	let transaction_pool = sc_transaction_pool::BasicPool::new_light(
+
+	let transaction_pool = Arc::new(sc_transaction_pool::BasicPool::new_light(
 		config.transaction_pool.clone(),
-		transaction_pool_api,
 		config.prometheus_registry(),
 		task_manager.spawn_handle(),
-	);
+		client.clone(),
+		on_demand.clone(),
+	));
 
 	let grandpa_block_import = sc_finality_grandpa::light_block_import(
 		client.clone(), backend.clone(), &(client.clone() as Arc<_>),
@@ -241,16 +236,42 @@ pub fn new_light(config: Configuration) -> Result<TaskManager, ServiceError> {
 	)?;
 
 	let finality_proof_provider =
-		Arc::new(GrandpaFinalityProofProvider::new(backend.clone(), client.clone() as Arc<_>));
+		GrandpaFinalityProofProvider::new_for_service(backend.clone(), client.clone());
 
-	sc_service::build(sc_service::ServiceParams {	
-		block_announce_validator_builder: None,
-		finality_proof_request_builder: Some(finality_proof_request_builder),
-		finality_proof_provider: Some(finality_proof_provider),
-		on_demand: Some(on_demand),
+	let (network, network_status_sinks, system_rpc_tx) =
+		sc_service::build_network(sc_service::BuildNetworkParams {
+			config: &config,
+			client: client.clone(),
+			transaction_pool: transaction_pool.clone(),
+			spawn_handle: task_manager.spawn_handle(),
+			import_queue,
+			on_demand: Some(on_demand.clone()),
+			block_announce_validator_builder: None,
+			finality_proof_request_builder: Some(finality_proof_request_builder),
+			finality_proof_provider: Some(finality_proof_provider),
+		})?;
+
+	if config.offchain_worker.enabled {
+		sc_service::build_offchain_workers(
+			&config, backend.clone(), task_manager.spawn_handle(), client.clone(), network.clone(),
+		);
+	}
+	
+	sc_service::spawn_tasks(sc_service::SpawnTasksParams {
 		remote_blockchain: Some(backend.remote_blockchain()),
+		transaction_pool,
+		task_manager: &mut task_manager,
+		on_demand: Some(on_demand),
 		rpc_extensions_builder: Box::new(|_| ()),
-		transaction_pool: Arc::new(transaction_pool),
-		config, client, import_queue, keystore, backend, task_manager
-	 }).map(|ServiceComponents { task_manager, .. }| task_manager)
+		telemetry_connection_sinks: sc_service::TelemetryConnectionSinks::default(),
+		config, 
+		client, 
+		keystore, 
+		backend, 
+		network, 
+		network_status_sinks, 
+		system_rpc_tx,
+	 })?;
+
+	 Ok(task_manager)
 }

substrate/bin/node/bench/src/txpool.rs

@@ -21,11 +21,11 @@
 //! The goal of this benchmark is to figure out time needed to fill
 //! the transaction pool for the next block.
 
-use std::{borrow::Cow, sync::Arc};
+use std::borrow::Cow;
 
 use node_testing::bench::{BenchDb, Profile, BlockType, KeyTypes, DatabaseType};
 
-use sc_transaction_pool::{BasicPool, FullChainApi};
+use sc_transaction_pool::BasicPool;
 use sp_runtime::generic::BlockId;
 use sp_transaction_pool::{TransactionPool, TransactionSource};
 
@@ -74,7 +74,6 @@ impl core::Benchmark for PoolBenchmark {
 		let executor = sp_core::testing::TaskExecutor::new();
 		let txpool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(context.client.clone(), None)),
 			None,
 			executor,
 			context.client.clone(),

substrate/bin/node/cli/src/command.rs

@@ -20,8 +20,8 @@ use crate::{chain_spec, service, Cli, Subcommand};
 use node_executor::Executor;
 use node_runtime::{Block, RuntimeApi};
 use sc_cli::{Result, SubstrateCli, RuntimeVersion, Role, ChainSpec};
-use sc_service::ServiceParams;
-use crate::service::new_full_params;
+use sc_service::PartialComponents;
+use crate::service::new_partial;
 
 impl SubstrateCli for Cli {
 	fn impl_name() -> String {
@@ -96,8 +96,8 @@ pub fn run() -> Result<()> {
 		Some(Subcommand::Base(subcommand)) => {
 			let runner = cli.create_runner(subcommand)?;
 			runner.run_subcommand(subcommand, |config| {
-				let (ServiceParams { client, backend, import_queue, task_manager, .. }, ..)
-					= new_full_params(config)?;
+				let PartialComponents { client, backend, task_manager, import_queue, ..}
+					= new_partial(&config)?;
 				Ok((client, backend, import_queue, task_manager))
 			})
 		}

substrate/bin/node/cli/src/service.rs

@@ -22,14 +22,12 @@
 
 use std::sync::Arc;
 use sc_consensus_babe;
-use grandpa::{
-	self, FinalityProofProvider as GrandpaFinalityProofProvider, StorageAndProofProvider,
-};
+use grandpa::{self, FinalityProofProvider as GrandpaFinalityProofProvider};
 use node_primitives::Block;
 use node_runtime::RuntimeApi;
 use sc_service::{
 	config::{Role, Configuration}, error::{Error as ServiceError},
-	RpcHandlers, ServiceComponents, TaskManager,
+	RpcHandlers, TaskManager,
 };
 use sp_inherents::InherentDataProviders;
 use sc_network::{Event, NetworkService};
@@ -46,34 +44,28 @@ type FullGrandpaBlockImport =
 	grandpa::GrandpaBlockImport<FullBackend, Block, FullClient, FullSelectChain>;
 type LightClient = sc_service::TLightClient<Block, RuntimeApi, Executor>;
 
-pub fn new_full_params(config: Configuration) -> Result<(
-	sc_service::ServiceParams<
-		Block, FullClient,
-		sc_consensus_babe::BabeImportQueue<Block, FullClient>,
-		sc_transaction_pool::FullPool<Block, FullClient>, node_rpc::IoHandler,
-		FullBackend
-	>,
+pub fn new_partial(config: &Configuration) -> Result<sc_service::PartialComponents<
+	FullClient, FullBackend, FullSelectChain,
+	sc_consensus_babe::BabeImportQueue<Block, FullClient>,
+	sc_transaction_pool::FullPool<Block, FullClient>,
 	(
-		sc_consensus_babe::BabeBlockImport<Block, FullClient, FullGrandpaBlockImport>,
-		grandpa::LinkHalf<Block, FullClient, FullSelectChain>,
-		sc_consensus_babe::BabeLink<Block>,
-	),
-	grandpa::SharedVoterState,
-	FullSelectChain,
-	InherentDataProviders
-), ServiceError> {
+		impl Fn(node_rpc::DenyUnsafe) -> node_rpc::IoHandler,
+		(
+			sc_consensus_babe::BabeBlockImport<Block, FullClient, FullGrandpaBlockImport>,
+			grandpa::LinkHalf<Block, FullClient, FullSelectChain>,
+			sc_consensus_babe::BabeLink<Block>,
+		),
+		grandpa::SharedVoterState,
+	)
+>, ServiceError> {
 	let (client, backend, keystore, task_manager) =
 		sc_service::new_full_parts::<Block, RuntimeApi, Executor>(&config)?;
 	let client = Arc::new(client);
 
 	let select_chain = sc_consensus::LongestChain::new(backend.clone());
 
-	let pool_api = sc_transaction_pool::FullChainApi::new(
-		client.clone(), config.prometheus_registry(),
-	);
 	let transaction_pool = sc_transaction_pool::BasicPool::new_full(
 		config.transaction_pool.clone(),
-		std::sync::Arc::new(pool_api),
 		config.prometheus_registry(),
 		task_manager.spawn_handle(),
 		client.clone(),
@@ -122,7 +114,7 @@ pub fn new_full_params(config: Configuration) -> Result<(
 		let select_chain = select_chain.clone();
 		let keystore = keystore.clone();
 
-		let rpc_extensions_builder = Box::new(move |deny_unsafe| {
+		let rpc_extensions_builder = move |deny_unsafe| {
 			let deps = node_rpc::FullDeps {
 				client: client.clone(),
 				pool: pool.clone(),
@@ -140,26 +132,16 @@ pub fn new_full_params(config: Configuration) -> Result<(
 			};
 
 			node_rpc::create_full(deps)
-		});
+		};
 
 		(rpc_extensions_builder, rpc_setup)
 	};
 
-	let provider = client.clone() as Arc<dyn grandpa::StorageAndProofProvider<_, _>>;
-	let finality_proof_provider =
-		Arc::new(grandpa::FinalityProofProvider::new(backend.clone(), provider));
-
-	let params = sc_service::ServiceParams {
-		config, backend, client, import_queue, keystore, task_manager, rpc_extensions_builder,
-		transaction_pool,
-		block_announce_validator_builder: None,
-		finality_proof_request_builder: None,
-		finality_proof_provider: Some(finality_proof_provider),
-		on_demand: None,
-		remote_blockchain: None,
-	};
-
-	Ok((params, import_setup, rpc_setup, select_chain, inherent_data_providers))
+	Ok(sc_service::PartialComponents {
+		client, backend, task_manager, keystore, select_chain, import_queue, transaction_pool,
+		inherent_data_providers,
+		other: (rpc_extensions_builder, import_setup, rpc_setup)
+	})
 }
 
 /// Creates a full service from the configuration.
@@ -174,31 +156,56 @@ pub fn new_full_base(
 	Arc<NetworkService<Block, <Block as BlockT>::Hash>>,
 	Arc<sc_transaction_pool::FullPool<Block, FullClient>>,
 ), ServiceError> {
-	let (params, import_setup, rpc_setup, select_chain, inherent_data_providers)
-		= new_full_params(config)?;
+	let sc_service::PartialComponents {
+		client, backend, mut task_manager, import_queue, keystore, select_chain, transaction_pool,
+		inherent_data_providers,
+		other: (rpc_extensions_builder, import_setup, rpc_setup),
+	} = new_partial(&config)?;
 
-	let (
-		role, force_authoring, name, enable_grandpa, prometheus_registry,
-		client, transaction_pool, keystore,
-	) = {
-		let sc_service::ServiceParams {
-			config, client, transaction_pool, keystore, ..
-		} = &params;
+	let finality_proof_provider =
+		GrandpaFinalityProofProvider::new_for_service(backend.clone(), client.clone());
+	
+	let (network, network_status_sinks, system_rpc_tx) =
+		sc_service::build_network(sc_service::BuildNetworkParams {
+			config: &config,
+			client: client.clone(),
+			transaction_pool: transaction_pool.clone(),
+			spawn_handle: task_manager.spawn_handle(),
+			import_queue,
+			on_demand: None,
+			block_announce_validator_builder: None,
+			finality_proof_request_builder: None,
+			finality_proof_provider: Some(finality_proof_provider.clone()),
+		})?;
 
-		(
-			config.role.clone(),
-			config.force_authoring,
-			config.network.node_name.clone(),
-			!config.disable_grandpa,
-			config.prometheus_registry().cloned(),
+	if config.offchain_worker.enabled {
+		sc_service::build_offchain_workers(
+			&config, backend.clone(), task_manager.spawn_handle(), client.clone(), network.clone(),
+		);
+	}
 
-			client.clone(), transaction_pool.clone(), keystore.clone(),
-		)
-	};
+	let role = config.role.clone();
+	let force_authoring = config.force_authoring;
+	let name = config.network.node_name.clone();
+	let enable_grandpa = !config.disable_grandpa;
+	let prometheus_registry = config.prometheus_registry().cloned();
+	let telemetry_connection_sinks = sc_service::TelemetryConnectionSinks::default();
 
-	let ServiceComponents {
-		task_manager, network, telemetry_on_connect_sinks, ..
-	} = sc_service::build(params)?;
+	sc_service::spawn_tasks(sc_service::SpawnTasksParams {
+		config,
+		backend: backend.clone(),
+		client: client.clone(),
+		keystore: keystore.clone(),
+		network: network.clone(),
+		rpc_extensions_builder: Box::new(rpc_extensions_builder),
+		transaction_pool: transaction_pool.clone(),
+		task_manager: &mut task_manager,
+		on_demand: None,
+		remote_blockchain: None,
+		telemetry_connection_sinks: telemetry_connection_sinks.clone(),
+		network_status_sinks,
+		system_rpc_tx,
+	})?;
 	
 	let (block_import, grandpa_link, babe_link) = import_setup;
 	let shared_voter_state = rpc_setup;
@@ -295,7 +302,7 @@ pub fn new_full_base(
 			link: grandpa_link,
 			network: network.clone(),
 			inherent_data_providers: inherent_data_providers.clone(),
-			telemetry_on_connect: Some(telemetry_on_connect_sinks.on_connect_stream()),
+			telemetry_on_connect: Some(telemetry_connection_sinks.on_connect_stream()),
 			voting_rule: grandpa::VotingRulesBuilder::default().build(),
 			prometheus_registry,
 			shared_voter_state,
@@ -331,20 +338,17 @@ pub fn new_light_base(config: Configuration) -> Result<(
 	Arc<NetworkService<Block, <Block as BlockT>::Hash>>,
 	Arc<sc_transaction_pool::LightPool<Block, LightClient, sc_network::config::OnDemand<Block>>>
 ), ServiceError> {
-	let (client, backend, keystore, task_manager, on_demand) =
+	let (client, backend, keystore, mut task_manager, on_demand) =
 		sc_service::new_light_parts::<Block, RuntimeApi, Executor>(&config)?;
 
 	let select_chain = sc_consensus::LongestChain::new(backend.clone());
 
-	let transaction_pool_api = Arc::new(sc_transaction_pool::LightChainApi::new(
-		client.clone(),
-		on_demand.clone(),
-	));
 	let transaction_pool = Arc::new(sc_transaction_pool::BasicPool::new_light(
 		config.transaction_pool.clone(),
-		transaction_pool_api,
 		config.prometheus_registry(),
 		task_manager.spawn_handle(),
+		client.clone(),
+		on_demand.clone(),
 	));
 
 	let grandpa_block_import = grandpa::light_block_import(
@@ -376,10 +380,27 @@ pub fn new_light_base(config: Configuration) -> Result<(
 		config.prometheus_registry(),
 	)?;
 
-	// GenesisAuthoritySetProvider is implemented for StorageAndProofProvider
-	let provider = client.clone() as Arc<dyn StorageAndProofProvider<_, _>>;
 	let finality_proof_provider =
-		Arc::new(GrandpaFinalityProofProvider::new(backend.clone(), provider));
+		GrandpaFinalityProofProvider::new_for_service(backend.clone(), client.clone());
+
+	let (network, network_status_sinks, system_rpc_tx) =
+		sc_service::build_network(sc_service::BuildNetworkParams {
+			config: &config,
+			client: client.clone(),
+			transaction_pool: transaction_pool.clone(),
+			spawn_handle: task_manager.spawn_handle(),
+			import_queue,
+			on_demand: Some(on_demand.clone()),
+			block_announce_validator_builder: None,
+			finality_proof_request_builder: Some(finality_proof_request_builder),
+			finality_proof_provider: Some(finality_proof_provider),
+		})?;
+	
+	if config.offchain_worker.enabled {
+		sc_service::build_offchain_workers(
+			&config, backend.clone(), task_manager.spawn_handle(), client.clone(), network.clone(),
+		);
+	}
 
 	let light_deps = node_rpc::LightDeps {
 		remote_blockchain: backend.remote_blockchain(),
@@ -390,17 +411,17 @@ pub fn new_light_base(config: Configuration) -> Result<(
 
 	let rpc_extensions = node_rpc::create_light(light_deps);
 
-	let ServiceComponents { task_manager, rpc_handlers, network, .. } =
-		sc_service::build(sc_service::ServiceParams {	
-			block_announce_validator_builder: None,
-			finality_proof_request_builder: Some(finality_proof_request_builder),
-			finality_proof_provider: Some(finality_proof_provider),
+	let rpc_handlers =
+		sc_service::spawn_tasks(sc_service::SpawnTasksParams {	
 			on_demand: Some(on_demand),
 			remote_blockchain: Some(backend.remote_blockchain()),
 			rpc_extensions_builder: Box::new(sc_service::NoopRpcExtensionBuilder(rpc_extensions)),
 			client: client.clone(),
 			transaction_pool: transaction_pool.clone(),
-			config, import_queue, keystore, backend, task_manager,
+			config, keystore, backend, network_status_sinks, system_rpc_tx,
+			network: network.clone(),
+			telemetry_connection_sinks: sc_service::TelemetryConnectionSinks::default(),
+			task_manager: &mut task_manager,
 		})?;
 	
 	Ok((task_manager, rpc_handlers, client, network, transaction_pool))

substrate/bin/node/rpc/src/lib.rs

@@ -45,8 +45,8 @@ use sc_consensus_babe::{Config, Epoch};
 use sc_consensus_babe_rpc::BabeRpcHandler;
 use sc_finality_grandpa::{SharedVoterState, SharedAuthoritySet};
 use sc_finality_grandpa_rpc::GrandpaRpcHandler;
-use sc_rpc_api::DenyUnsafe;
 use sp_block_builder::BlockBuilder;
+pub use sc_rpc_api::DenyUnsafe;
 
 /// Light client extra dependencies.
 pub struct LightDeps<C, F, P> {

substrate/client/basic-authorship/src/basic_authorship.rs

@@ -326,7 +326,7 @@ mod tests {
 		prelude::*, TestClientBuilder, runtime::{Extrinsic, Transfer}, TestClientBuilderExt,
 	};
 	use sp_transaction_pool::{ChainEvent, MaintainedTransactionPool, TransactionSource};
-	use sc_transaction_pool::{BasicPool, FullChainApi};
+	use sc_transaction_pool::BasicPool;
 	use sp_api::Core;
 	use sp_blockchain::HeaderBackend;
 	use sp_runtime::traits::NumberFor;
@@ -361,7 +361,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let txpool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),
@@ -415,7 +414,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let txpool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),
@@ -451,7 +449,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let txpool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),
@@ -514,7 +511,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let txpool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),

substrate/client/basic-authorship/src/lib.rs

@@ -34,7 +34,6 @@
 //! # let spawner = sp_core::testing::TaskExecutor::new();
 //! # let txpool = BasicPool::new_full(
 //! #     Default::default(),
-//! #     Arc::new(FullChainApi::new(client.clone(), None)),
 //! #     None,
 //! #     spawner,
 //! #     client.clone(),

substrate/client/finality-grandpa/src/finality_proof.rs

@@ -169,6 +169,18 @@ impl<B, Block: BlockT> FinalityProofProvider<B, Block>
 	{
 		FinalityProofProvider { backend, authority_provider: Arc::new(authority_provider) }
 	}
+
+	/// Create new finality proof provider for the service using:
+	///
+	/// - backend for accessing blockchain data;
+	/// - storage_and_proof_provider, which is generally a client.
+	pub fn new_for_service(
+		backend: Arc<B>,
+		storage_and_proof_provider: Arc<dyn StorageAndProofProvider<Block, B>>,
+	) -> Arc<Self> {
+		Arc::new(Self::new(backend, storage_and_proof_provider))
+	}
+
 }
 
 impl<B, Block> sc_network::config::FinalityProofProvider<Block> for FinalityProofProvider<B, Block>

substrate/client/offchain/src/lib.rs

@@ -250,7 +250,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = TestPool(BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),

substrate/client/rpc/src/author/tests.rs

@@ -64,7 +64,6 @@ impl Default for TestSetup {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),

substrate/client/service/Cargo.toml

@@ -53,6 +53,7 @@ sp-session = { version = "2.0.0-rc5", path = "../../primitives/session" }
 sp-state-machine = { version = "0.8.0-rc5", path = "../../primitives/state-machine" }
 sp-application-crypto = { version = "2.0.0-rc5", path = "../../primitives/application-crypto" }
 sp-consensus = { version = "0.8.0-rc5", path = "../../primitives/consensus/common" }
+sp-inherents = { version = "2.0.0-rc5", path = "../../primitives/inherents" }
 sc-network = { version = "0.8.0-rc5", path = "../network" }
 sc-chain-spec = { version = "2.0.0-rc5", path = "../chain-spec" }
 sc-light = { version = "2.0.0-rc5", path = "../light" }

substrate/client/service/src/builder.rs

@@ -18,37 +18,35 @@
 
 use crate::{
 	NetworkStatus, NetworkState, error::Error, DEFAULT_PROTOCOL_ID, MallocSizeOfWasm,
+	TelemetryConnectionSinks, RpcHandlers, NetworkStatusSinks,
 	start_rpc_servers, build_network_future, TransactionPoolAdapter, TaskManager, SpawnTaskHandle,
 	status_sinks, metrics::MetricsService,
 	client::{light, Client, ClientConfig},
-	config::{Configuration, KeystoreConfig, PrometheusConfig, OffchainWorkerConfig},
+	config::{Configuration, KeystoreConfig, PrometheusConfig},
 };
 use sc_client_api::{
 	light::RemoteBlockchain, ForkBlocks, BadBlocks, UsageProvider, ExecutorProvider,
 };
-use sp_utils::mpsc::{tracing_unbounded, TracingUnboundedSender, TracingUnboundedReceiver};
+use sp_utils::mpsc::{tracing_unbounded, TracingUnboundedSender};
 use sc_chain_spec::get_extension;
 use sp_consensus::{
 	block_validation::{BlockAnnounceValidator, DefaultBlockAnnounceValidator, Chain},
 	import_queue::ImportQueue,
 };
-use futures::{
-	Future, FutureExt, StreamExt,
-	future::ready,
-};
+use futures::{FutureExt, StreamExt, future::ready};
 use jsonrpc_pubsub::manager::SubscriptionManager;
 use sc_keystore::Store as Keystore;
 use log::{info, warn, error};
 use sc_network::config::{Role, FinalityProofProvider, OnDemand, BoxFinalityProofRequestBuilder};
 use sc_network::NetworkService;
-use parking_lot::{Mutex, RwLock};
+use parking_lot::RwLock;
 use sp_runtime::generic::BlockId;
 use sp_runtime::traits::{
 	Block as BlockT, SaturatedConversion, HashFor, Zero, BlockIdTo,
 };
 use sp_api::{ProvideRuntimeApi, CallApiAt};
 use sc_executor::{NativeExecutor, NativeExecutionDispatch, RuntimeInfo};
-use std::{collections::HashMap, sync::Arc, pin::Pin};
+use std::{collections::HashMap, sync::Arc};
 use wasm_timer::SystemTime;
 use sc_telemetry::{telemetry, SUBSTRATE_INFO};
 use sp_transaction_pool::MaintainedTransactionPool;
@@ -63,7 +61,6 @@ use sc_client_api::{
 	execution_extensions::ExecutionExtensions
 };
 use sp_blockchain::{HeaderMetadata, HeaderBackend};
-use crate::{ServiceComponents, TelemetryOnConnectSinks, RpcHandlers, NetworkStatusSinks};
 
 /// A utility trait for building an RPC extension given a `DenyUnsafe` instance.
 /// This is useful since at service definition time we don't know whether the
@@ -371,7 +368,7 @@ pub fn new_client<E, Block, RA>(
 }
 
 /// Parameters to pass into `build`.
-pub struct ServiceParams<TBl: BlockT, TCl, TImpQu, TExPool, TRpc, Backend> {
+pub struct SpawnTasksParams<'a, TBl: BlockT, TCl, TExPool, TRpc, Backend> {
 	/// The service configuration.
 	pub config: Configuration,
 	/// A shared client returned by `new_full_parts`/`new_light_parts`.
@@ -379,17 +376,11 @@ pub struct ServiceParams<TBl: BlockT, TCl, TImpQu, TExPool, TRpc, Backend> {
 	/// A shared backend returned by `new_full_parts`/`new_light_parts`.
 	pub backend: Arc<Backend>,
 	/// A task manager returned by `new_full_parts`/`new_light_parts`.
-	pub task_manager: TaskManager,
+	pub task_manager: &'a mut TaskManager,
 	/// A shared keystore returned by `new_full_parts`/`new_light_parts`.
 	pub keystore: Arc<RwLock<Keystore>>,
 	/// An optional, shared data fetcher for light clients.
 	pub on_demand: Option<Arc<OnDemand<TBl>>>,
-	/// An import queue.
-	pub import_queue: TImpQu,
-	/// An optional finality proof request builder.
-	pub finality_proof_request_builder: Option<BoxFinalityProofRequestBuilder<TBl>>,
-	/// An optional, shared finality proof request provider.
-	pub finality_proof_provider: Option<Arc<dyn FinalityProofProvider<TBl>>>,
 	/// A shared transaction pool.
 	pub transaction_pool: Arc<TExPool>,
 	/// A RPC extension builder. Use `NoopRpcExtensionBuilder` if you just want to pass in the
@@ -397,15 +388,61 @@ pub struct ServiceParams<TBl: BlockT, TCl, TImpQu, TExPool, TRpc, Backend> {
 	pub rpc_extensions_builder: Box<dyn RpcExtensionBuilder<Output = TRpc> + Send>,
 	/// An optional, shared remote blockchain instance. Used for light clients.
 	pub remote_blockchain: Option<Arc<dyn RemoteBlockchain<TBl>>>,
-	/// A block annouce validator builder.
-	pub block_announce_validator_builder:
-		Option<Box<dyn FnOnce(Arc<TCl>) -> Box<dyn BlockAnnounceValidator<TBl> + Send> + Send>>,
+	/// A shared network instance.
+	pub network: Arc<NetworkService<TBl, <TBl as BlockT>::Hash>>,
+	/// Sinks to propagate network status updates.
+	pub network_status_sinks: NetworkStatusSinks<TBl>,
+	/// A Sender for RPC requests.
+	pub system_rpc_tx: TracingUnboundedSender<sc_rpc::system::Request<TBl>>,
+	/// Shared Telemetry connection sinks,
+	pub telemetry_connection_sinks: TelemetryConnectionSinks,
 }
 
-/// Put together the components of a service from the parameters.
-pub fn build<TBl, TBackend, TImpQu, TExPool, TRpc, TCl>(
-	builder: ServiceParams<TBl, TCl, TImpQu, TExPool, TRpc, TBackend>,
-) -> Result<ServiceComponents<TBl, TBackend, TCl>, Error>
+/// Build a shared offchain workers instance.
+pub fn build_offchain_workers<TBl, TBackend, TCl>(
+	config: &Configuration,
+	backend: Arc<TBackend>,
+	spawn_handle: SpawnTaskHandle,
+	client: Arc<TCl>,
+	network: Arc<NetworkService<TBl, <TBl as BlockT>::Hash>>,
+) -> Option<Arc<sc_offchain::OffchainWorkers<TCl, TBackend::OffchainStorage, TBl>>>
+	where
+		TBl: BlockT, TBackend: sc_client_api::Backend<TBl>,
+		<TBackend as sc_client_api::Backend<TBl>>::OffchainStorage: 'static,
+		TCl: Send + Sync + ProvideRuntimeApi<TBl> + BlockchainEvents<TBl> + 'static,
+		<TCl as ProvideRuntimeApi<TBl>>::Api: sc_offchain::OffchainWorkerApi<TBl>,
+{
+	let offchain_workers = match backend.offchain_storage() {
+		Some(db) => {
+			Some(Arc::new(sc_offchain::OffchainWorkers::new(client.clone(), db)))
+		},
+		None => {
+			warn!("Offchain workers disabled, due to lack of offchain storage support in backend.");
+			None
+		},
+	};
+
+	// Inform the offchain worker about new imported blocks
+	if let Some(offchain) = offchain_workers.clone() {
+		spawn_handle.spawn(
+			"offchain-notifications",
+			sc_offchain::notification_future(
+				config.role.is_authority(),
+				client.clone(),
+				offchain,
+				Clone::clone(&spawn_handle),
+				network.clone()
+			)
+		);
+	}
+
+	offchain_workers
+}
+
+/// Spawn the tasks that are required to run a node.
+pub fn spawn_tasks<TBl, TBackend, TExPool, TRpc, TCl>(
+	params: SpawnTasksParams<TBl, TCl, TExPool, TRpc, TBackend>,
+) -> Result<Arc<RpcHandlers>, Error>
 	where
 		TCl: ProvideRuntimeApi<TBl> + HeaderMetadata<TBl, Error=sp_blockchain::Error> + Chain<TBl> +
 		BlockBackend<TBl> + BlockIdTo<TBl, Error=sp_blockchain::Error> + ProofProvider<TBl> +
@@ -421,26 +458,23 @@ pub fn build<TBl, TBackend, TImpQu, TExPool, TRpc, TCl>(
 			sp_api::ApiExt<TBl, StateBackend = TBackend::State>,
 		TBl: BlockT,
 		TBackend: 'static + sc_client_api::backend::Backend<TBl> + Send,
-		TImpQu: 'static + ImportQueue<TBl>,
 		TExPool: MaintainedTransactionPool<Block=TBl, Hash = <TBl as BlockT>::Hash> +
 			MallocSizeOfWasm + 'static,
 		TRpc: sc_rpc::RpcExtension<sc_rpc::Metadata>
 {
-	let ServiceParams {
+	let SpawnTasksParams {
 		mut config,
-		mut task_manager,
+		task_manager,
 		client,
 		on_demand,
 		backend,
 		keystore,
-		import_queue,
-		finality_proof_request_builder,
-		finality_proof_provider,
 		transaction_pool,
 		rpc_extensions_builder,
 		remote_blockchain,
-		block_announce_validator_builder,
-	} = builder;
+		network, network_status_sinks, system_rpc_tx,
+		telemetry_connection_sinks,
+	} = params;
 
 	let chain_info = client.usage_info().chain;
 
@@ -458,57 +492,14 @@ pub fn build<TBl, TBackend, TImpQu, TExPool, TRpc, TCl>(
 		"best" => ?chain_info.best_hash
 	);
 
-	let (system_rpc_tx, system_rpc_rx) = tracing_unbounded("mpsc_system_rpc");
-
-	let (network, network_status_sinks, network_future) = build_network(
-		&config, client.clone(), transaction_pool.clone(), task_manager.spawn_handle(),
-		on_demand.clone(), block_announce_validator_builder, finality_proof_request_builder,
-		finality_proof_provider, system_rpc_rx, import_queue
-	)?;
-
 	let spawn_handle = task_manager.spawn_handle();
 
-	// The network worker is responsible for gathering all network messages and processing
-	// them. This is quite a heavy task, and at the time of the writing of this comment it
-	// frequently happens that this future takes several seconds or in some situations
-	// even more than a minute until it has processed its entire queue. This is clearly an
-	// issue, and ideally we would like to fix the network future to take as little time as
-	// possible, but we also take the extra harm-prevention measure to execute the networking
-	// future using `spawn_blocking`.
-	spawn_handle.spawn_blocking("network-worker", network_future);
-
-	let offchain_storage = backend.offchain_storage();
-	let offchain_workers = match (config.offchain_worker.clone(), offchain_storage.clone()) {
-		(OffchainWorkerConfig {enabled: true, .. }, Some(db)) => {
-			Some(Arc::new(sc_offchain::OffchainWorkers::new(client.clone(), db)))
-		},
-		(OffchainWorkerConfig {enabled: true, .. }, None) => {
-			warn!("Offchain workers disabled, due to lack of offchain storage support in backend.");
-			None
-		},
-		_ => None,
-	};
-
 	// Inform the tx pool about imported and finalized blocks.
 	spawn_handle.spawn(
 		"txpool-notifications",
 		sc_transaction_pool::notification_future(client.clone(), transaction_pool.clone()),
 	);
 
-	// Inform the offchain worker about new imported blocks
-	if let Some(offchain) = offchain_workers.clone() {
-		spawn_handle.spawn(
-			"offchain-notifications",
-			sc_offchain::notification_future(
-				config.role.is_authority(),
-				client.clone(),
-				offchain,
-				task_manager.spawn_handle(),
-				network.clone()
-			)
-		);
-	}
-
 	spawn_handle.spawn(
 		"on-transaction-imported",
 		transaction_notifications(transaction_pool.clone(), network.clone()),
@@ -545,14 +536,12 @@ pub fn build<TBl, TBackend, TImpQu, TExPool, TRpc, TCl>(
 	let gen_handler = |deny_unsafe: sc_rpc::DenyUnsafe| gen_handler(
 		deny_unsafe, &config, task_manager.spawn_handle(), client.clone(), transaction_pool.clone(),
 		keystore.clone(), on_demand.clone(), remote_blockchain.clone(), &*rpc_extensions_builder,
-		offchain_storage.clone(), system_rpc_tx.clone()
+		backend.offchain_storage(), system_rpc_tx.clone()
 	);
 	let rpc = start_rpc_servers(&config, gen_handler)?;
 	// This is used internally, so don't restrict access to unsafe RPC
 	let rpc_handlers = Arc::new(RpcHandlers(gen_handler(sc_rpc::DenyUnsafe::No)));
 
-	let telemetry_connection_sinks: Arc<Mutex<Vec<TracingUnboundedSender<()>>>> = Default::default();
-
 	// Telemetry
 	let telemetry = config.telemetry_endpoints.clone().and_then(|endpoints| {
 		if endpoints.is_empty() {
@@ -585,18 +574,14 @@ pub fn build<TBl, TBackend, TImpQu, TExPool, TRpc, TCl>(
 	// Spawn informant task
 	spawn_handle.spawn("informant", sc_informant::build(
 		client.clone(),
-		network_status_sinks.clone(),
+		network_status_sinks.clone().0,
 		transaction_pool.clone(),
 		config.informant_output_format,
 	));
 
 	task_manager.keep_alive((telemetry, config.base_path, rpc, rpc_handlers.clone()));
 
-	Ok(ServiceComponents {
-		task_manager, network, rpc_handlers, offchain_workers,
-		telemetry_on_connect_sinks: TelemetryOnConnectSinks(telemetry_connection_sinks),
-		network_status_sinks: NetworkStatusSinks::new(network_status_sinks),
-	})
+	Ok(rpc_handlers)
 }
 
 async fn transaction_notifications<TBl, TExPool>(
@@ -626,7 +611,7 @@ async fn telemetry_periodic_send<TBl, TExPool, TCl>(
 	client: Arc<TCl>,
 	transaction_pool: Arc<TExPool>,
 	mut metrics_service: MetricsService,
-	network_status_sinks: Arc<status_sinks::StatusSinks<(NetworkStatus<TBl>, NetworkState)>>
+	network_status_sinks: NetworkStatusSinks<TBl>,
 )
 	where
 		TBl: BlockT,
@@ -634,7 +619,7 @@ async fn telemetry_periodic_send<TBl, TExPool, TCl>(
 		TExPool: MaintainedTransactionPool<Block=TBl, Hash = <TBl as BlockT>::Hash>,
 {
 	let (state_tx, state_rx) = tracing_unbounded::<(NetworkStatus<_>, NetworkState)>("mpsc_netstat1");
-	network_status_sinks.push(std::time::Duration::from_millis(5000), state_tx);
+	network_status_sinks.0.push(std::time::Duration::from_millis(5000), state_tx);
 	state_rx.for_each(move |(net_status, _)| {
 		let info = client.usage_info();
 		metrics_service.tick(
@@ -647,11 +632,11 @@ async fn telemetry_periodic_send<TBl, TExPool, TCl>(
 }
 
 async fn telemetry_periodic_network_state<TBl: BlockT>(
-	network_status_sinks: Arc<status_sinks::StatusSinks<(NetworkStatus<TBl>, NetworkState)>>
+	network_status_sinks: NetworkStatusSinks<TBl>,
 ) {
 	// Periodically send the network state to the telemetry.
 	let (netstat_tx, netstat_rx) = tracing_unbounded::<(NetworkStatus<_>, NetworkState)>("mpsc_netstat2");
-	network_status_sinks.push(std::time::Duration::from_secs(30), netstat_tx);
+	network_status_sinks.0.push(std::time::Duration::from_secs(30), netstat_tx);
 	netstat_rx.for_each(move |(_, network_state)| {
 		telemetry!(
 			SUBSTRATE_INFO;
@@ -665,7 +650,7 @@ async fn telemetry_periodic_network_state<TBl: BlockT>(
 fn build_telemetry<TBl: BlockT>(
 	config: &mut Configuration,
 	endpoints: sc_telemetry::TelemetryEndpoints,
-	telemetry_connection_sinks: Arc<Mutex<Vec<TracingUnboundedSender<()>>>>,
+	telemetry_connection_sinks: TelemetryConnectionSinks,
 	network: Arc<NetworkService<TBl, <TBl as BlockT>::Hash>>,
 	spawn_handle: SpawnTaskHandle,
 	genesis_hash: <TBl as BlockT>::Hash,
@@ -703,7 +688,7 @@ fn build_telemetry<TBl: BlockT>(
 					"network_id" => network_id.clone()
 				);
 
-				telemetry_connection_sinks.lock().retain(|sink| {
+				telemetry_connection_sinks.0.lock().retain(|sink| {
 					sink.unbounded_send(()).is_ok()
 				});
 				ready(())
@@ -805,24 +790,38 @@ fn gen_handler<TBl, TBackend, TExPool, TRpc, TCl>(
 	))
 }
 
-fn build_network<TBl, TExPool, TImpQu, TCl>(
-	config: &Configuration,
-	client: Arc<TCl>,
-	transaction_pool: Arc<TExPool>,
-	spawn_handle: SpawnTaskHandle,
-	on_demand: Option<Arc<OnDemand<TBl>>>,
-	block_announce_validator_builder: Option<Box<
+/// Parameters to pass into `build_network`.
+pub struct BuildNetworkParams<'a, TBl: BlockT, TExPool, TImpQu, TCl> {
+	/// The service configuration.
+	pub config: &'a Configuration,
+	/// A shared client returned by `new_full_parts`/`new_light_parts`.
+	pub client: Arc<TCl>,
+	/// A shared transaction pool.
+	pub transaction_pool: Arc<TExPool>,
+	/// A handle for spawning tasks.
+	pub spawn_handle: SpawnTaskHandle,
+	/// An import queue.
+	pub import_queue: TImpQu,
+	/// An optional, shared data fetcher for light clients.
+	pub on_demand: Option<Arc<OnDemand<TBl>>>,
+	/// A block annouce validator builder.
+	pub block_announce_validator_builder: Option<Box<
 		dyn FnOnce(Arc<TCl>) -> Box<dyn BlockAnnounceValidator<TBl> + Send> + Send
 	>>,
-	finality_proof_request_builder: Option<BoxFinalityProofRequestBuilder<TBl>>,
-	finality_proof_provider: Option<Arc<dyn FinalityProofProvider<TBl>>>,
-	system_rpc_rx: TracingUnboundedReceiver<sc_rpc::system::Request<TBl>>,
-	import_queue: TImpQu
+	/// An optional finality proof request builder.
+	pub finality_proof_request_builder: Option<BoxFinalityProofRequestBuilder<TBl>>,
+	/// An optional, shared finality proof request provider.
+	pub finality_proof_provider: Option<Arc<dyn FinalityProofProvider<TBl>>>,
+}
+
+/// Build the network service, the network status sinks and an RPC sender.
+pub fn build_network<TBl, TExPool, TImpQu, TCl>(
+	params: BuildNetworkParams<TBl, TExPool, TImpQu, TCl>
 ) -> Result<
 	(
 		Arc<NetworkService<TBl, <TBl as BlockT>::Hash>>,
-		Arc<status_sinks::StatusSinks<(NetworkStatus<TBl>, NetworkState)>>,
-		Pin<Box<dyn Future<Output = ()> + Send>>
+		NetworkStatusSinks<TBl>,
+		TracingUnboundedSender<sc_rpc::system::Request<TBl>>,
 	),
 	Error
 >
@@ -834,6 +833,11 @@ fn build_network<TBl, TExPool, TImpQu, TCl>(
 		TExPool: MaintainedTransactionPool<Block=TBl, Hash = <TBl as BlockT>::Hash> + 'static,
 		TImpQu: ImportQueue<TBl> + 'static,
 {
+	let BuildNetworkParams {
+		config, client, transaction_pool, spawn_handle, import_queue, on_demand,
+		block_announce_validator_builder, finality_proof_request_builder, finality_proof_provider,
+	} = params;
+
 	let transaction_pool_adapter = Arc::new(TransactionPoolAdapter {
 		imports_external_transactions: !matches!(config.role, Role::Light),
 		pool: transaction_pool,
@@ -862,6 +866,7 @@ fn build_network<TBl, TExPool, TImpQu, TCl>(
 	let network_params = sc_network::config::Params {
 		role: config.role.clone(),
 		executor: {
+			let spawn_handle = Clone::clone(&spawn_handle);
 			Some(Box::new(move |fut| {
 				spawn_handle.spawn("libp2p-node", fut);
 			}))
@@ -881,7 +886,9 @@ fn build_network<TBl, TExPool, TImpQu, TCl>(
 	let has_bootnodes = !network_params.network_config.boot_nodes.is_empty();
 	let network_mut = sc_network::NetworkWorker::new(network_params)?;
 	let network = network_mut.service().clone();
-	let network_status_sinks = Arc::new(status_sinks::StatusSinks::new());
+	let network_status_sinks = NetworkStatusSinks::new(Arc::new(status_sinks::StatusSinks::new()));
+
+	let (system_rpc_tx, system_rpc_rx) = tracing_unbounded("mpsc_system_rpc");
 
 	let future = build_network_future(
 		config.role.clone(),
@@ -891,7 +898,16 @@ fn build_network<TBl, TExPool, TImpQu, TCl>(
 		system_rpc_rx,
 		has_bootnodes,
 		config.announce_block,
-	).boxed();
+	);
 
-	Ok((network, network_status_sinks, future))
+	// The network worker is responsible for gathering all network messages and processing
+	// them. This is quite a heavy task, and at the time of the writing of this comment it
+	// frequently happens that this future takes several seconds or in some situations
+	// even more than a minute until it has processed its entire queue. This is clearly an
+	// issue, and ideally we would like to fix the network future to take as little time as
+	// possible, but we also take the extra harm-prevention measure to execute the networking
+	// future using `spawn_blocking`.
+	spawn_handle.spawn_blocking("network-worker", future);
+
+	Ok((network, network_status_sinks, system_rpc_tx))
 }

substrate/client/service/src/lib.rs

@@ -52,8 +52,9 @@ use sp_utils::{status_sinks, mpsc::{tracing_unbounded, TracingUnboundedReceiver,
 
 pub use self::error::Error;
 pub use self::builder::{
-	new_full_client, new_client, new_full_parts, new_light_parts, build,
-	ServiceParams, TFullClient, TLightClient, TFullBackend, TLightBackend,
+	new_full_client, new_client, new_full_parts, new_light_parts,
+	spawn_tasks, build_network, BuildNetworkParams, build_offchain_workers,
+	SpawnTasksParams, TFullClient, TLightClient, TFullBackend, TLightBackend,
 	TLightBackendWithHash, TLightClientWithBackend,
 	TFullCallExecutor, TLightCallExecutor, RpcExtensionBuilder, NoopRpcExtensionBuilder,
 };
@@ -79,7 +80,8 @@ pub use sc_tracing::TracingReceiver;
 pub use task_manager::SpawnTaskHandle;
 pub use task_manager::TaskManager;
 pub use sp_consensus::import_queue::ImportQueue;
-use sc_client_api::{Backend, BlockchainEvents};
+use sc_client_api::BlockchainEvents;
+pub use sc_keystore::KeyStorePtr as KeyStore;
 
 const DEFAULT_PROTOCOL_ID: &str = "sup";
 
@@ -117,6 +119,7 @@ impl RpcHandlers {
 
 /// Sinks to propagate network status updates.
 /// For each element, every time the `Interval` fires we push an element on the sender.
+#[derive(Clone)]
 pub struct NetworkStatusSinks<Block: BlockT>(
 	Arc<status_sinks::StatusSinks<(NetworkStatus<Block>, NetworkState)>>,
 );
@@ -138,9 +141,10 @@ impl<Block: BlockT> NetworkStatusSinks<Block> {
 }
 
 /// Sinks to propagate telemetry connection established events.
-pub struct TelemetryOnConnectSinks(pub Arc<Mutex<Vec<TracingUnboundedSender<()>>>>);
+#[derive(Default, Clone)]
+pub struct TelemetryConnectionSinks(Arc<Mutex<Vec<TracingUnboundedSender<()>>>>);
 
-impl TelemetryOnConnectSinks {
+impl TelemetryConnectionSinks {
 	/// Get event stream for telemetry connection established events.
 	pub fn on_connect_stream(&self) -> TracingUnboundedReceiver<()> {
 		let (sink, stream) =tracing_unbounded("mpsc_telemetry_on_connect");
@@ -149,23 +153,26 @@ impl TelemetryOnConnectSinks {
 	}
 }
 
-/// The individual components of the chain, built by the service builder. You are encouraged to
-/// deconstruct this into its fields.
-pub struct ServiceComponents<TBl: BlockT, TBackend: Backend<TBl>, TCl> {
+/// An imcomplete set of chain components, but enough to run the chain ops subcommands.
+pub struct PartialComponents<Client, Backend, SelectChain, ImportQueue, TransactionPool, Other> {
+	/// A shared client instance.
+	pub client: Arc<Client>,
+	/// A shared backend instance.
+	pub backend: Arc<Backend>,
 	/// The chain task manager.
 	pub task_manager: TaskManager,
-	/// A shared network instance.
-	pub network: Arc<sc_network::NetworkService<TBl, <TBl as BlockT>::Hash>>,
-	/// RPC handlers that can perform RPC queries.
-	pub rpc_handlers: Arc<RpcHandlers>,
-	/// Sinks to propagate network status updates.
-	pub network_status_sinks: NetworkStatusSinks<TBl>,
-	/// Shared Telemetry connection sinks,
-	pub telemetry_on_connect_sinks: TelemetryOnConnectSinks,
-	/// A shared offchain workers instance.
-	pub offchain_workers: Option<Arc<sc_offchain::OffchainWorkers<
-		TCl, TBackend::OffchainStorage, TBl
-	>>>,
+	/// A shared keystore instance.
+	pub keystore: KeyStore,
+	/// A chain selection algorithm instance.
+	pub select_chain: SelectChain,
+	/// An import queue.
+	pub import_queue: ImportQueue,
+	/// A shared transaction pool.
+	pub transaction_pool: Arc<TransactionPool>,
+	/// A registry of all providers of `InherentData`.
+	pub inherent_data_providers: sp_inherents::InherentDataProviders,
+	/// Everything else that needs to be passed into the main build function.
+	pub other: Other,
 }
 
 /// Builds a never-ending future that continuously polls the network.
@@ -179,7 +186,7 @@ async fn build_network_future<
 	role: Role,
 	mut network: sc_network::NetworkWorker<B, H>,
 	client: Arc<C>,
-	status_sinks: Arc<status_sinks::StatusSinks<(NetworkStatus<B>, NetworkState)>>,
+	status_sinks: NetworkStatusSinks<B>,
 	mut rpc_rx: TracingUnboundedReceiver<sc_rpc::system::Request<B>>,
 	should_have_peers: bool,
 	announce_imported_blocks: bool,
@@ -308,7 +315,7 @@ async fn build_network_future<
 
 			// At a regular interval, we send the state of the network on what is called
 			// the "status sinks".
-			ready_sink = status_sinks.next().fuse() => {
+			ready_sink = status_sinks.0.next().fuse() => {
 				let status = NetworkStatus {
 					sync_state: network.sync_state(),
 					best_seen_block: network.best_seen_block(),
@@ -549,7 +556,7 @@ mod tests {
 	use sp_consensus::SelectChain;
 	use sp_runtime::traits::BlindCheckable;
 	use substrate_test_runtime_client::{prelude::*, runtime::{Extrinsic, Transfer}};
-	use sc_transaction_pool::{BasicPool, FullChainApi};
+	use sc_transaction_pool::BasicPool;
 
 	#[test]
 	fn should_not_propagate_transactions_that_are_marked_as_such() {
@@ -559,7 +566,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),

substrate/client/transaction-pool/src/lib.rs

@@ -180,18 +180,6 @@ impl<PoolApi, Block> BasicPool<PoolApi, Block>
 		)
 	}
 
-	/// Create new basic transaction pool for a light node with the provided api.
-	pub fn new_light(
-		options: sc_transaction_graph::Options,
-		pool_api: Arc<PoolApi>,
-		prometheus: Option<&PrometheusRegistry>,
-		spawner: impl SpawnNamed,
-	) -> Self {
-		Self::with_revalidation_type(
-			options, pool_api, prometheus, RevalidationType::Light, spawner,
-		)
-	}
-
 	/// Create new basic transaction pool with provided api and custom
 	/// revalidation type.
 	pub fn with_revalidation_type(
@@ -342,7 +330,28 @@ impl<PoolApi, Block> TransactionPool for BasicPool<PoolApi, Block>
 	}
 }
 
-impl<Block, Client> BasicPool<FullChainApi<Client, Block>, Block>
+impl<Block, Client, Fetcher> LightPool<Block, Client, Fetcher>
+where
+	Block: BlockT,
+	Client: sp_blockchain::HeaderBackend<Block> + 'static,
+	Fetcher: sc_client_api::Fetcher<Block> + 'static,
+{
+	/// Create new basic transaction pool for a light node with the provided api.
+	pub fn new_light(
+		options: sc_transaction_graph::Options,
+		prometheus: Option<&PrometheusRegistry>,
+		spawner: impl SpawnNamed,
+		client: Arc<Client>,
+		fetcher: Arc<Fetcher>,
+	) -> Self {
+		let pool_api = Arc::new(LightChainApi::new(client, fetcher));
+		Self::with_revalidation_type(
+			options, pool_api, prometheus, RevalidationType::Light, spawner,
+		)
+	}
+}
+
+impl<Block, Client> FullPool<Block, Client>
 where
 	Block: BlockT,
 	Client: sp_api::ProvideRuntimeApi<Block>
@@ -355,11 +364,11 @@ where
 	/// Create new basic transaction pool for a full node with the provided api.
 	pub fn new_full(
 		options: sc_transaction_graph::Options,
-		pool_api: Arc<FullChainApi<Client, Block>>,
 		prometheus: Option<&PrometheusRegistry>,
 		spawner: impl SpawnNamed,
 		client: Arc<Client>,
 	) -> Arc<Self> {
+		let pool_api = Arc::new(FullChainApi::new(client.clone(), prometheus));
 		let pool = Arc::new(Self::with_revalidation_type(
 			options, pool_api, prometheus, RevalidationType::Full, spawner
 		));

substrate/utils/frame/rpc/system/src/lib.rs

@@ -289,7 +289,7 @@ mod tests {
 
 	use futures::executor::block_on;
 	use substrate_test_runtime_client::{runtime::Transfer, AccountKeyring};
-	use sc_transaction_pool::{BasicPool, FullChainApi};
+	use sc_transaction_pool::BasicPool;
 	use sp_runtime::{ApplyExtrinsicResult, transaction_validity::{TransactionValidityError, InvalidTransaction}};
 
 	#[test]
@@ -301,7 +301,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),
@@ -341,7 +340,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),
@@ -365,7 +363,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),
@@ -398,7 +395,6 @@ mod tests {
 		let spawner = sp_core::testing::TaskExecutor::new();
 		let pool = BasicPool::new_full(
 			Default::default(),
-			Arc::new(FullChainApi::new(client.clone(), None)),
 			None,
 			spawner,
 			client.clone(),