node: exit on GRANDPA voter or BABE authoring error (#3353)

* node: exit on GRANDPA voter or BABE authoring error

* node: exit process with non-zero return code when service fails

* service: rename infallible task to essential task

* service: revert field name changes

* core: fix service testnet

substrate/node/cli/src/lib.rs

@@ -223,11 +223,11 @@ fn run_until_exit<T, C, E>(
 	mut runtime: Runtime,
 	service: T,
 	e: E,
-) -> error::Result<()>
-	where
-		T: Deref<Target=substrate_service::Service<C>> + Future<Item = (), Error = ()> + Send + 'static,
-		C: substrate_service::Components,
-		E: IntoExit,
+) -> error::Result<()> where
+	T: Deref<Target=substrate_service::Service<C>>,
+	T: Future<Item = (), Error = substrate_service::error::Error> + Send + 'static,
+	C: substrate_service::Components,
+	E: IntoExit,
 {
 	let (exit_send, exit) = exit_future::signal();
 
@@ -238,11 +238,17 @@ fn run_until_exit<T, C, E>(
 	// but we need to keep holding a reference to the global telemetry guard
 	let _telemetry = service.telemetry();
 
-	let _ = runtime.block_on(service.select(e.into_exit()));
+	let service_res = {
+		let exit = e.into_exit().map_err(|_| error::Error::Other("Exit future failed.".into()));
+		let service = service.map_err(|err| error::Error::Service(err));
+		let select = service.select(exit).map(|_| ()).map_err(|(err, _)| err);
+		runtime.block_on(select)
+	};
+
 	exit_send.fire();
 
 	// TODO [andre]: timeout this future #1318
 	let _ = runtime.shutdown_on_idle().wait();
 
-	Ok(())
+	service_res
 }

substrate/node/cli/src/service.rs

@@ -152,7 +152,10 @@ construct_service_factory! {
 
 					let babe = start_babe(babe_config)?;
 					let select = babe.select(service.on_exit()).then(|_| Ok(()));
-					service.spawn_task(Box::new(select));
+
+					// the BABE authoring task is considered infallible, i.e. if it
+					// fails we take down the service with it.
+					service.spawn_essential_task(select);
 				}
 
 				let config = grandpa::Config {
@@ -187,7 +190,10 @@ construct_service_factory! {
 							on_exit: service.on_exit(),
 							telemetry_on_connect: Some(telemetry_on_connect),
 						};
-						service.spawn_task(Box::new(grandpa::run_grandpa_voter(grandpa_config)?));
+
+						// the GRANDPA voter task is considered infallible, i.e.
+						// if it fails we take down the service with it.
+						service.spawn_essential_task(grandpa::run_grandpa_voter(grandpa_config)?);
 					},
 					(_, true) => {
 						grandpa::setup_disabled_grandpa(