Change SpawnedSubsystem type to log subsystem errors (#1878)

* Change SpawnedSubsystem type to log subsystem errors

* Remove clone

polkadot/node/core/av-store/src/lib.rs

@@ -27,7 +27,7 @@ use std::sync::Arc;
 use std::time::{Duration, SystemTime, SystemTimeError, UNIX_EPOCH};
 
 use codec::{Encode, Decode};
-use futures::{select, channel::oneshot, future::{self, Either}, Future, FutureExt};
+use futures::{select, channel::oneshot, future::{self, Either}, Future, FutureExt, TryFutureExt};
 use futures_timer::Delay;
 use kvdb_rocksdb::{Database, DatabaseConfig};
 use kvdb::{KeyValueDB, DBTransaction};
@@ -969,9 +969,7 @@ where
 {
 	fn start(self, ctx: Context) -> SpawnedSubsystem {
 		let future = run(self, ctx)
-			.map(|r| if let Err(e) = r {
-				log::error!(target: "availabilitystore", "Subsystem exited with an error {:?}", e);
-			})
+			.map_err(|e| SubsystemError::with_origin("availability-store", e))
 			.boxed();
 
 		SpawnedSubsystem {

polkadot/node/core/candidate-validation/src/lib.rs

@@ -121,7 +121,6 @@ impl<S, C> Subsystem<C> for CandidateValidationSubsystem<S> where
 	fn start(self, ctx: C) -> SpawnedSubsystem {
 		let future = run(ctx, self.spawn, self.metrics)
 			.map_err(|e| SubsystemError::with_origin("candidate-validation", e))
-			.map(|_| ())
 			.boxed();
 		SpawnedSubsystem {
 			name: "candidate-validation-subsystem",

polkadot/node/core/chain-api/src/lib.rs

@@ -67,7 +67,6 @@ impl<Client, Context> Subsystem<Context> for ChainApiSubsystem<Client> where
 	fn start(self, ctx: Context) -> SpawnedSubsystem {
 		let future = run(ctx, self)
 			.map_err(|e| SubsystemError::with_origin("chain-api", e))
-			.map(|_| ())
 			.boxed();
 		SpawnedSubsystem {
 			future,

polkadot/node/core/runtime-api/src/lib.rs

@@ -60,7 +60,7 @@ impl<Client, Context> Subsystem<Context> for RuntimeApiSubsystem<Client> where
 {
 	fn start(self, ctx: Context) -> SpawnedSubsystem {
 		SpawnedSubsystem {
-			future: run(ctx, self).map(|_| ()).boxed(),
+			future: run(ctx, self).boxed(),
 			name: "runtime-api-subsystem",
 		}
 	}