Simplify subsystem jobs (#2037)

* Simplify subsystem jobs

This pr simplifies the subsystem jobs interface. Instead of requiring an
extra message that is used to signal that a job should be ended, a job
now ends when the receiver returns `None`. Besides that it changes the
interface to enforce that messages to a job provide a relay parent.

* Drop ToJobTrait

* Remove FromJob

We always convert this message to FromJobCommand anyway.

polkadot/node/core/backing/src/lib.rs

@@ -40,8 +40,7 @@ use polkadot_subsystem::{
 	messages::{
 		AllMessages, AvailabilityStoreMessage, CandidateBackingMessage, CandidateSelectionMessage,
 		CandidateValidationMessage, NewBackedCandidate, PoVDistributionMessage, ProvisionableData,
-		ProvisionerMessage, RuntimeApiMessage, StatementDistributionMessage, ValidationFailed,
-		RuntimeApiRequest,
+		ProvisionerMessage, StatementDistributionMessage, ValidationFailed, RuntimeApiRequest,
 	},
 };
 use polkadot_node_subsystem_util::{
@@ -93,9 +92,9 @@ struct CandidateBackingJob {
 	/// The hash of the relay parent on top of which this job is doing it's work.
 	parent: Hash,
 	/// Inbound message channel receiving part.
-	rx_to: mpsc::Receiver<ToJob>,
+	rx_to: mpsc::Receiver<CandidateBackingMessage>,
 	/// Outbound message channel sending part.
-	tx_from: mpsc::Sender<FromJob>,
+	tx_from: mpsc::Sender<FromJobCommand>,
 	/// The `ParaId` assigned to this validator
 	assignment: ParaId,
 	/// The collator required to author the candidate, if any.
@@ -151,84 +150,6 @@ impl TableContextTrait for TableContext {
 	}
 }
 
-/// A message type that is sent from `CandidateBackingSubsystem` to `CandidateBackingJob`.
-pub enum ToJob {
-	/// A `CandidateBackingMessage`.
-	CandidateBacking(CandidateBackingMessage),
-	/// Stop working.
-	Stop,
-}
-
-impl TryFrom<AllMessages> for ToJob {
-	type Error = ();
-
-	fn try_from(msg: AllMessages) -> Result<Self, Self::Error> {
-		match msg {
-			AllMessages::CandidateBacking(msg) => Ok(ToJob::CandidateBacking(msg)),
-			_ => Err(()),
-		}
-	}
-}
-
-impl From<CandidateBackingMessage> for ToJob {
-	fn from(msg: CandidateBackingMessage) -> Self {
-		Self::CandidateBacking(msg)
-	}
-}
-
-impl util::ToJobTrait for ToJob {
-	const STOP: Self = ToJob::Stop;
-
-	fn relay_parent(&self) -> Option<Hash> {
-		match self {
-			Self::CandidateBacking(cb) => cb.relay_parent(),
-			Self::Stop => None,
-		}
-	}
-}
-
-/// A message type that is sent from `CandidateBackingJob` to `CandidateBackingSubsystem`.
-enum FromJob {
-	AvailabilityStore(AvailabilityStoreMessage),
-	RuntimeApiMessage(RuntimeApiMessage),
-	CandidateValidation(CandidateValidationMessage),
-	CandidateSelection(CandidateSelectionMessage),
-	Provisioner(ProvisionerMessage),
-	PoVDistribution(PoVDistributionMessage),
-	StatementDistribution(StatementDistributionMessage),
-}
-
-impl From<FromJob> for FromJobCommand {
-	fn from(f: FromJob) -> FromJobCommand {
-		FromJobCommand::SendMessage(match f {
-			FromJob::AvailabilityStore(msg) => AllMessages::AvailabilityStore(msg),
-			FromJob::RuntimeApiMessage(msg) => AllMessages::RuntimeApi(msg),
-			FromJob::CandidateValidation(msg) => AllMessages::CandidateValidation(msg),
-			FromJob::CandidateSelection(msg) => AllMessages::CandidateSelection(msg),
-			FromJob::StatementDistribution(msg) => AllMessages::StatementDistribution(msg),
-			FromJob::PoVDistribution(msg) => AllMessages::PoVDistribution(msg),
-			FromJob::Provisioner(msg) => AllMessages::Provisioner(msg),
-		})
-	}
-}
-
-impl TryFrom<AllMessages> for FromJob {
-	type Error = &'static str;
-
-	fn try_from(f: AllMessages) -> Result<Self, Self::Error> {
-		match f {
-			AllMessages::AvailabilityStore(msg) => Ok(FromJob::AvailabilityStore(msg)),
-			AllMessages::RuntimeApi(msg) => Ok(FromJob::RuntimeApiMessage(msg)),
-			AllMessages::CandidateValidation(msg) => Ok(FromJob::CandidateValidation(msg)),
-			AllMessages::CandidateSelection(msg) => Ok(FromJob::CandidateSelection(msg)),
-			AllMessages::StatementDistribution(msg) => Ok(FromJob::StatementDistribution(msg)),
-			AllMessages::PoVDistribution(msg) => Ok(FromJob::PoVDistribution(msg)),
-			AllMessages::Provisioner(msg) => Ok(FromJob::Provisioner(msg)),
-			_ => Err("can't convert this AllMessages variant to FromJob"),
-		}
-	}
-}
-
 struct InvalidErasureRoot;
 
 // It looks like it's not possible to do an `impl From` given the current state of
@@ -301,12 +222,10 @@ fn table_attested_to_backed(
 impl CandidateBackingJob {
 	/// Run asynchronously.
 	async fn run_loop(mut self) -> Result<(), Error> {
-		while let Some(msg) = self.rx_to.next().await {
-			match msg {
-				ToJob::CandidateBacking(msg) => {
-					self.process_msg(msg).await?;
-				}
-				ToJob::Stop => break,
+		loop {
+			match self.rx_to.next().await  {
+				Some(msg) => self.process_msg(msg).await?,
+				None => break,
 			}
 		}
 
@@ -317,9 +236,7 @@ impl CandidateBackingJob {
 		&mut self,
 		candidate: CandidateReceipt,
 	) -> Result<(), Error> {
-		self.tx_from.send(FromJob::CandidateSelection(
-			CandidateSelectionMessage::Invalid(self.parent, candidate)
-		)).await?;
+		self.tx_from.send(AllMessages::from(CandidateSelectionMessage::Invalid(self.parent, candidate)).into()).await?;
 
 		Ok(())
 	}
@@ -664,7 +581,7 @@ impl CandidateBackingJob {
 	}
 
 	async fn send_to_provisioner(&mut self, msg: ProvisionerMessage) -> Result<(), Error> {
-		self.tx_from.send(FromJob::Provisioner(msg)).await?;
+		self.tx_from.send(AllMessages::from(msg).into()).await?;
 
 		Ok(())
 	}
@@ -674,9 +591,9 @@ impl CandidateBackingJob {
 		descriptor: CandidateDescriptor,
 		pov: Arc<PoV>,
 	) -> Result<(), Error> {
-		self.tx_from.send(FromJob::PoVDistribution(
+		self.tx_from.send(AllMessages::from(
 			PoVDistributionMessage::DistributePoV(self.parent, descriptor, pov),
-		)).await.map_err(Into::into)
+		).into()).await.map_err(Into::into)
 	}
 
 	async fn request_pov_from_distribution(
@@ -685,9 +602,9 @@ impl CandidateBackingJob {
 	) -> Result<Arc<PoV>, Error> {
 		let (tx, rx) = oneshot::channel();
 
-		self.tx_from.send(FromJob::PoVDistribution(
+		self.tx_from.send(AllMessages::from(
 			PoVDistributionMessage::FetchPoV(self.parent, descriptor, tx)
-		)).await?;
+		).into()).await?;
 
 		Ok(rx.await?)
 	}
@@ -699,13 +616,14 @@ impl CandidateBackingJob {
 	) -> Result<ValidationResult, Error> {
 		let (tx, rx) = oneshot::channel();
 
-		self.tx_from.send(FromJob::CandidateValidation(
+		self.tx_from.send(
+			AllMessages::from(
 				CandidateValidationMessage::ValidateFromChainState(
 					candidate,
 					pov,
 					tx,
 				)
-			)
+			).into(),
 		).await?;
 
 		Ok(rx.await??)
@@ -719,7 +637,7 @@ impl CandidateBackingJob {
 		available_data: AvailableData,
 	) -> Result<(), Error> {
 		let (tx, rx) = oneshot::channel();
-		self.tx_from.send(FromJob::AvailabilityStore(
+		self.tx_from.send(AllMessages::from(
 				AvailabilityStoreMessage::StoreAvailableData(
 					candidate_hash,
 					id,
@@ -727,7 +645,7 @@ impl CandidateBackingJob {
 					available_data,
 					tx,
 				)
-			)
+			).into(),
 		).await?;
 
 		let _ = rx.await?;
@@ -777,15 +695,14 @@ impl CandidateBackingJob {
 	async fn distribute_signed_statement(&mut self, s: SignedFullStatement) -> Result<(), Error> {
 		let smsg = StatementDistributionMessage::Share(self.parent, s);
 
-		self.tx_from.send(FromJob::StatementDistribution(smsg)).await?;
+		self.tx_from.send(AllMessages::from(smsg).into()).await?;
 
 		Ok(())
 	}
 }
 
 impl util::JobTrait for CandidateBackingJob {
-	type ToJob = ToJob;
-	type FromJob = FromJob;
+	type ToJob = CandidateBackingMessage;
 	type Error = Error;
 	type RunArgs = SyncCryptoStorePtr;
 	type Metrics = Metrics;
@@ -798,7 +715,7 @@ impl util::JobTrait for CandidateBackingJob {
 		keystore: SyncCryptoStorePtr,
 		metrics: Metrics,
 		rx_to: mpsc::Receiver<Self::ToJob>,
-		mut tx_from: mpsc::Sender<Self::FromJob>,
+		mut tx_from: mpsc::Sender<FromJobCommand>,
 	) -> Pin<Box<dyn Future<Output = Result<(), Self::Error>> + Send>> {
 		async move {
 			macro_rules! try_runtime_api {
@@ -1000,7 +917,7 @@ impl metrics::Metrics for Metrics {
 	}
 }
 
-delegated_subsystem!(CandidateBackingJob(SyncCryptoStorePtr, Metrics) <- ToJob as CandidateBackingSubsystem);
+delegated_subsystem!(CandidateBackingJob(SyncCryptoStorePtr, Metrics) <- CandidateBackingMessage as CandidateBackingSubsystem);
 
 #[cfg(test)]
 mod tests {
@@ -1013,7 +930,7 @@ mod tests {
 		GroupRotationInfo,
 	};
 	use polkadot_subsystem::{
-		messages::RuntimeApiRequest,
+		messages::{RuntimeApiRequest, RuntimeApiMessage},
 		ActiveLeavesUpdate, FromOverseer, OverseerSignal,
 	};
 	use polkadot_node_primitives::InvalidCandidate;