Remove network starter that is no longer needed (#6400)

# Description

This seems to be an old artifact of the long closed
paritytech/substrate#6827 that I noticed when
working on related code earlier.

## Integration

`NetworkStarter` was removed, simply remove its usage:
```diff
-let (network, system_rpc_tx, tx_handler_controller, start_network, sync_service) =
+let (network, system_rpc_tx, tx_handler_controller, sync_service) =
    build_network(BuildNetworkParams {
...
-start_network.start_network();
```

## Review Notes

Changes are trivial, the only reason for this to not be accepted is if
it is desired to not start network automatically for whatever reason, in
which case the description of network starter needs to change.

# Checklist

* [x] My PR includes a detailed description as outlined in the
"Description" and its two subsections above.
* [ ] My PR follows the [labeling requirements](

https://github.com/paritytech/polkadot-sdk/blob/master/docs/contributor/CONTRIBUTING.md#Process
) of this project (at minimum one label for `T` required)
* External contributors: ask maintainers to put the right label on your
PR.

---------

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

cumulus/client/relay-chain-minimal-node/src/lib.rs

@@ -224,7 +224,7 @@ async fn new_minimal_relay_chain<Block: BlockT, Network: NetworkBackend<RelayBlo
 		.chain_get_header(None)
 		.await?
 		.ok_or_else(|| RelayChainError::RpcCallError("Unable to fetch best header".to_string()))?;
-	let (network, network_starter, sync_service) = build_collator_network::<Network>(
+	let (network, sync_service) = build_collator_network::<Network>(
 		&config,
 		net_config,
 		task_manager.spawn_handle(),
@@ -262,8 +262,6 @@ async fn new_minimal_relay_chain<Block: BlockT, Network: NetworkBackend<RelayBlo
 	let overseer_handle =
 		collator_overseer::spawn_overseer(overseer_args, &task_manager, relay_chain_rpc_client)?;
 
-	network_starter.start_network();
-
 	Ok(NewMinimalNode { task_manager, overseer_handle })
 }
 

cumulus/client/relay-chain-minimal-node/src/network.rs

@@ -29,7 +29,7 @@ use sc_network::{
 
 use sc_network::{config::FullNetworkConfiguration, NetworkBackend, NotificationService};
 use sc_network_common::{role::Roles, sync::message::BlockAnnouncesHandshake};
-use sc_service::{error::Error, Configuration, NetworkStarter, SpawnTaskHandle};
+use sc_service::{error::Error, Configuration, SpawnTaskHandle};
 
 use std::{iter, sync::Arc};
 
@@ -41,10 +41,7 @@ pub(crate) fn build_collator_network<Network: NetworkBackend<Block, Hash>>(
 	genesis_hash: Hash,
 	best_header: Header,
 	notification_metrics: NotificationMetrics,
-) -> Result<
-	(Arc<dyn NetworkService>, NetworkStarter, Arc<dyn sp_consensus::SyncOracle + Send + Sync>),
-	Error,
-> {
+) -> Result<(Arc<dyn NetworkService>, Arc<dyn sp_consensus::SyncOracle + Send + Sync>), Error> {
 	let protocol_id = config.protocol_id();
 	let (block_announce_config, _notification_service) = get_block_announce_proto_config::<Network>(
 		protocol_id.clone(),
@@ -85,31 +82,16 @@ pub(crate) fn build_collator_network<Network: NetworkBackend<Block, Hash>>(
 	let network_worker = Network::new(network_params)?;
 	let network_service = network_worker.network_service();
 
-	let (network_start_tx, network_start_rx) = futures::channel::oneshot::channel();
-
 	// 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", Some("networking"), async move {
-		if network_start_rx.await.is_err() {
-			tracing::warn!(
-				"The NetworkStart returned as part of `build_network` has been silently dropped"
-			);
-			// This `return` might seem unnecessary, but we don't want to make it look like
-			// everything is working as normal even though the user is clearly misusing the API.
-			return
-		}
-
-		network_worker.run().await;
-	});
-
-	let network_starter = NetworkStarter::new(network_start_tx);
+	spawn_handle.spawn_blocking("network-worker", Some("networking"), network_worker.run());
 
-	Ok((network_service, network_starter, Arc::new(SyncOracle {})))
+	Ok((network_service, Arc::new(SyncOracle {})))
 }
 
 fn adjust_network_config_light_in_peers(config: &mut NetworkConfiguration) {

cumulus/client/service/src/lib.rs

@@ -40,7 +40,7 @@ use sc_consensus::{
 use sc_network::{config::SyncMode, service::traits::NetworkService, NetworkBackend};
 use sc_network_sync::SyncingService;
 use sc_network_transactions::TransactionsHandlerController;
-use sc_service::{Configuration, NetworkStarter, SpawnTaskHandle, TaskManager, WarpSyncConfig};
+use sc_service::{Configuration, SpawnTaskHandle, TaskManager, WarpSyncConfig};
 use sc_telemetry::{log, TelemetryWorkerHandle};
 use sc_utils::mpsc::TracingUnboundedSender;
 use sp_api::ProvideRuntimeApi;
@@ -439,7 +439,6 @@ pub async fn build_network<'a, Block, Client, RCInterface, IQ, Network>(
 	Arc<dyn NetworkService>,
 	TracingUnboundedSender<sc_rpc::system::Request<Block>>,
 	TransactionsHandlerController<Block::Hash>,
-	NetworkStarter,
 	Arc<SyncingService<Block>>,
 )>
 where

cumulus/polkadot-omni-node/lib/src/common/spec.rs

@@ -239,7 +239,7 @@ pub(crate) trait NodeSpec: BaseNodeSpec {
 					prometheus_registry.clone(),
 				);
 
-				let (network, system_rpc_tx, tx_handler_controller, start_network, sync_service) =
+				let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 					build_network(BuildNetworkParams {
 						parachain_config: &parachain_config,
 						net_config,
@@ -346,8 +346,6 @@ pub(crate) trait NodeSpec: BaseNodeSpec {
 					)?;
 				}
 
-				start_network.start_network();
-
 				Ok(task_manager)
 			}
 			.instrument(sc_tracing::tracing::info_span!(

cumulus/polkadot-omni-node/lib/src/nodes/manual_seal.rs

@@ -93,7 +93,7 @@ impl<NodeSpec: NodeSpecT> ManualSealNode<NodeSpec> {
 			config.prometheus_config.as_ref().map(|cfg| &cfg.registry),
 		);
 
-		let (network, system_rpc_tx, tx_handler_controller, start_network, sync_service) =
+		let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 			sc_service::build_network(sc_service::BuildNetworkParams {
 				config: &config,
 				client: client.clone(),
@@ -219,7 +219,6 @@ impl<NodeSpec: NodeSpecT> ManualSealNode<NodeSpec> {
 			telemetry: telemetry.as_mut(),
 		})?;
 
-		start_network.start_network();
 		Ok(task_manager)
 	}
 }

cumulus/test/service/src/lib.rs

@@ -367,7 +367,7 @@ where
 		prometheus_registry.clone(),
 	);
 
-	let (network, system_rpc_tx, tx_handler_controller, start_network, sync_service) =
+	let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 		build_network(BuildNetworkParams {
 			parachain_config: &parachain_config,
 			net_config,
@@ -542,8 +542,6 @@ where
 		}
 	}
 
-	start_network.start_network();
-
 	Ok((task_manager, client, network, rpc_handlers, transaction_pool, backend))
 }
 

polkadot/node/service/src/lib.rs

@@ -1003,7 +1003,7 @@ pub fn new_full<
 		})
 	};
 
-	let (network, system_rpc_tx, tx_handler_controller, network_starter, sync_service) =
+	let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 		sc_service::build_network(sc_service::BuildNetworkParams {
 			config: &config,
 			net_config,
@@ -1383,8 +1383,6 @@ pub fn new_full<
 		);
 	}
 
-	network_starter.start_network();
-
 	Ok(NewFull {
 		task_manager,
 		client,

prdoc/pr_6400.prdoc

@@ -0,0 +1,41 @@
+title: Remove network starter that is no longer needed
+doc:
+- audience: Node Dev
+  description: |-
+    # Description
+
+    This seems to be an old artifact of the long closed https://github.com/paritytech/substrate/issues/6827 that I noticed when working on related code earlier.
+
+    ## Integration
+
+    `NetworkStarter` was removed, simply remove its usage:
+    ```diff
+    -let (network, system_rpc_tx, tx_handler_controller, start_network, sync_service) =
+    +let (network, system_rpc_tx, tx_handler_controller, sync_service) =
+        build_network(BuildNetworkParams {
+    ...
+    -start_network.start_network();
+    ```
+
+    ## Review Notes
+
+    Changes are trivial, the only reason for this to not be accepted is if it is desired to not start network automatically for whatever reason, in which case the description of network starter needs to change.
+
+    # Checklist
+
+    * [x] My PR includes a detailed description as outlined in the "Description" and its two subsections above.
+    * [ ] My PR follows the [labeling requirements](
+    https://github.com/paritytech/polkadot-sdk/blob/master/docs/contributor/CONTRIBUTING.md#Process
+    ) of this project (at minimum one label for `T` required)
+        * External contributors: ask maintainers to put the right label on your PR.
+crates:
+- name: cumulus-relay-chain-minimal-node
+  bump: major
+- name: cumulus-client-service
+  bump: major
+- name: polkadot-omni-node-lib
+  bump: major
+- name: polkadot-service
+  bump: major
+- name: sc-service
+  bump: major

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

@@ -513,7 +513,7 @@ pub fn new_full_base<N: NetworkBackend<Block, <Block as BlockT>::Hash>>(
 		Vec::default(),
 	));
 
-	let (network, system_rpc_tx, tx_handler_controller, network_starter, sync_service) =
+	let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 		sc_service::build_network(sc_service::BuildNetworkParams {
 			config: &config,
 			net_config,
@@ -801,7 +801,6 @@ pub fn new_full_base<N: NetworkBackend<Block, <Block as BlockT>::Hash>>(
 		);
 	}
 
-	network_starter.start_network();
 	Ok(NewFullBase {
 		task_manager,
 		client,

substrate/client/service/src/builder.rs

@@ -25,7 +25,7 @@ use crate::{
 	start_rpc_servers, BuildGenesisBlock, GenesisBlockBuilder, RpcHandlers, SpawnTaskHandle,
 	TaskManager, TransactionPoolAdapter,
 };
-use futures::{channel::oneshot, future::ready, FutureExt, StreamExt};
+use futures::{future::ready, FutureExt, StreamExt};
 use jsonrpsee::RpcModule;
 use log::info;
 use prometheus_endpoint::Registry;
@@ -822,7 +822,6 @@ pub fn build_network<Block, Net, TxPool, IQ, Client>(
 		Arc<dyn sc_network::service::traits::NetworkService>,
 		TracingUnboundedSender<sc_rpc::system::Request<Block>>,
 		sc_network_transactions::TransactionsHandlerController<<Block as BlockT>::Hash>,
-		NetworkStarter,
 		Arc<SyncingService<Block>>,
 	),
 	Error,
@@ -984,7 +983,6 @@ pub fn build_network_advanced<Block, Net, TxPool, IQ, Client>(
 		Arc<dyn sc_network::service::traits::NetworkService>,
 		TracingUnboundedSender<sc_rpc::system::Request<Block>>,
 		sc_network_transactions::TransactionsHandlerController<<Block as BlockT>::Hash>,
-		NetworkStarter,
 		Arc<SyncingService<Block>>,
 	),
 	Error,
@@ -1125,49 +1123,16 @@ where
 		announce_block,
 	);
 
-	// TODO: Normally, one is supposed to pass a list of notifications protocols supported by the
-	// node through the `NetworkConfiguration` struct. But because this function doesn't know in
-	// advance which components, such as GrandPa or Polkadot, will be plugged on top of the
-	// service, it is unfortunately not possible to do so without some deep refactoring. To
-	// bypass this problem, the `NetworkService` provides a `register_notifications_protocol`
-	// method that can be called even after the network has been initialized. However, we want to
-	// avoid the situation where `register_notifications_protocol` is called *after* the network
-	// actually connects to other peers. For this reason, we delay the process of the network
-	// future until the user calls `NetworkStarter::start_network`.
-	//
-	// This entire hack should eventually be removed in favour of passing the list of protocols
-	// through the configuration.
-	//
-	// See also https://github.com/paritytech/substrate/issues/6827
-	let (network_start_tx, network_start_rx) = oneshot::channel();
-
 	// 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", Some("networking"), async move {
-		if network_start_rx.await.is_err() {
-			log::warn!(
-				"The NetworkStart returned as part of `build_network` has been silently dropped"
-			);
-			// This `return` might seem unnecessary, but we don't want to make it look like
-			// everything is working as normal even though the user is clearly misusing the API.
-			return
-		}
-
-		future.await
-	});
+	spawn_handle.spawn_blocking("network-worker", Some("networking"), future);
 
-	Ok((
-		network,
-		system_rpc_tx,
-		tx_handler_controller,
-		NetworkStarter(network_start_tx),
-		sync_service.clone(),
-	))
+	Ok((network, system_rpc_tx, tx_handler_controller, sync_service.clone()))
 }
 
 /// Configuration for [`build_default_syncing_engine`].
@@ -1396,21 +1361,3 @@ where
 		warp_sync_protocol_name,
 	)?))
 }
-
-/// Object used to start the network.
-#[must_use]
-pub struct NetworkStarter(oneshot::Sender<()>);
-
-impl NetworkStarter {
-	/// Create a new NetworkStarter
-	pub fn new(sender: oneshot::Sender<()>) -> Self {
-		NetworkStarter(sender)
-	}
-
-	/// Start the network. Call this after all sub-components have been initialized.
-	///
-	/// > **Note**: If you don't call this function, the networking will not work.
-	pub fn start_network(self) {
-		let _ = self.0.send(());
-	}
-}

substrate/client/service/src/lib.rs

@@ -64,8 +64,8 @@ pub use self::{
 		new_client, new_db_backend, new_full_client, new_full_parts, new_full_parts_record_import,
 		new_full_parts_with_genesis_builder, new_wasm_executor,
 		propagate_transaction_notifications, spawn_tasks, BuildNetworkAdvancedParams,
-		BuildNetworkParams, DefaultSyncingEngineConfig, KeystoreContainer, NetworkStarter,
-		SpawnTasksParams, TFullBackend, TFullCallExecutor, TFullClient,
+		BuildNetworkParams, DefaultSyncingEngineConfig, KeystoreContainer, SpawnTasksParams,
+		TFullBackend, TFullCallExecutor, TFullClient,
 	},
 	client::{ClientConfig, LocalCallExecutor},
 	error::Error,

templates/minimal/node/src/service.rs

@@ -134,7 +134,7 @@ pub fn new_full<Network: sc_network::NetworkBackend<Block, <Block as BlockT>::Ha
 		config.prometheus_config.as_ref().map(|cfg| &cfg.registry),
 	);
 
-	let (network, system_rpc_tx, tx_handler_controller, network_starter, sync_service) =
+	let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 		sc_service::build_network(sc_service::BuildNetworkParams {
 			config: &config,
 			net_config,
@@ -264,6 +264,5 @@ pub fn new_full<Network: sc_network::NetworkBackend<Block, <Block as BlockT>::Ha
 		_ => {},
 	}
 
-	network_starter.start_network();
 	Ok(task_manager)
 }

templates/parachain/node/src/service.rs

@@ -270,7 +270,7 @@ pub async fn start_parachain_node(
 
 	// NOTE: because we use Aura here explicitly, we can use `CollatorSybilResistance::Resistant`
 	// when starting the network.
-	let (network, system_rpc_tx, tx_handler_controller, start_network, sync_service) =
+	let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 		build_network(BuildNetworkParams {
 			parachain_config: &parachain_config,
 			net_config,
@@ -406,7 +406,5 @@ pub async fn start_parachain_node(
 		)?;
 	}
 
-	start_network.start_network();
-
 	Ok((task_manager, client))
 }

templates/solochain/node/src/service.rs

@@ -169,7 +169,7 @@ pub fn new_full<
 		Vec::default(),
 	));
 
-	let (network, system_rpc_tx, tx_handler_controller, network_starter, sync_service) =
+	let (network, system_rpc_tx, tx_handler_controller, sync_service) =
 		sc_service::build_network(sc_service::BuildNetworkParams {
 			config: &config,
 			net_config,
@@ -329,6 +329,5 @@ pub fn new_full<
 		);
 	}
 
-	network_starter.start_network();
 	Ok(task_manager)
 }