Remove background_tasks field in ServiceBuilder (#5830)

* Spawn tasks instead of pushing them to background_tasks

* Remove unnecessary mut keyword for self

* Remove background_tasks field in ServiceBuilder

substrate/client/service/src/builder.rs

@@ -96,7 +96,6 @@ pub struct ServiceBuilder<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp,
 	rpc_extensions: TRpc,
 	remote_backend: Option<Arc<dyn RemoteBlockchain<TBl>>>,
 	marker: PhantomData<(TBl, TRtApi)>,
-	background_tasks: Vec<(&'static str, BackgroundTask)>,
 	block_announce_validator_builder: Option<Box<dyn FnOnce(Arc<TCl>) -> Box<dyn BlockAnnounceValidator<TBl> + Send> + Send>>,
 }
 
@@ -311,7 +310,6 @@ impl ServiceBuilder<(), (), (), (), (), (), (), (), (), (), ()> {
 			transaction_pool: Arc::new(()),
 			rpc_extensions: Default::default(),
 			remote_backend: None,
-			background_tasks: Default::default(),
 			block_announce_validator_builder: None,
 			marker: PhantomData,
 		})
@@ -395,7 +393,6 @@ impl ServiceBuilder<(), (), (), (), (), (), (), (), (), (), ()> {
 			transaction_pool: Arc::new(()),
 			rpc_extensions: Default::default(),
 			remote_backend: Some(remote_blockchain),
-			background_tasks: Default::default(),
 			block_announce_validator_builder: None,
 			marker: PhantomData,
 		})
@@ -469,7 +466,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: self.transaction_pool,
 			rpc_extensions: self.rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: self.block_announce_validator_builder,
 			marker: self.marker,
 		})
@@ -514,7 +510,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: self.transaction_pool,
 			rpc_extensions: self.rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: self.block_announce_validator_builder,
 			marker: self.marker,
 		})
@@ -553,7 +548,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: self.transaction_pool,
 			rpc_extensions: self.rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: self.block_announce_validator_builder,
 			marker: self.marker,
 		})
@@ -618,7 +612,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: self.transaction_pool,
 			rpc_extensions: self.rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: self.block_announce_validator_builder,
 			marker: self.marker,
 		})
@@ -647,7 +640,7 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 
 	/// Defines which transaction pool to use.
 	pub fn with_transaction_pool<UExPool>(
-		mut self,
+		self,
 		transaction_pool_builder: impl FnOnce(
 			sc_transaction_pool::txpool::Options,
 			Arc<TCl>,
@@ -665,7 +658,7 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 		)?;
 
 		if let Some(background_task) = background_task{
-			self.background_tasks.push(("txpool-background", background_task));
+			self.task_manager.spawn_handle().spawn("txpool-background", background_task);
 		}
 
 		Ok(ServiceBuilder {
@@ -682,7 +675,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: Arc::new(transaction_pool),
 			rpc_extensions: self.rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: self.block_announce_validator_builder,
 			marker: self.marker,
 		})
@@ -711,7 +703,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: self.transaction_pool,
 			rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: self.block_announce_validator_builder,
 			marker: self.marker,
 		})
@@ -740,7 +731,6 @@ impl<TBl, TRtApi, TCl, TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend>
 			transaction_pool: self.transaction_pool,
 			rpc_extensions: self.rpc_extensions,
 			remote_backend: self.remote_backend,
-			background_tasks: self.background_tasks,
 			block_announce_validator_builder: Some(Box::new(block_announce_validator_builder)),
 			marker: self.marker,
 		})
@@ -852,7 +842,6 @@ ServiceBuilder<
 			transaction_pool,
 			rpc_extensions,
 			remote_backend,
-			background_tasks,
 			block_announce_validator_builder,
 		} = self;
 
@@ -947,12 +936,6 @@ ServiceBuilder<
 
 		let spawn_handle = task_manager.spawn_handle();
 
-		// Spawn background tasks which were stacked during the
-		// service building.
-		for (title, background_task) in background_tasks {
-			spawn_handle.spawn(title, background_task);
-		}
-
 		{
 			// block notifications
 			let txpool = Arc::downgrade(&transaction_pool);