Request based PoV distribution (#2640)

* Indentation fix.

* Prepare request-response for PoV fetching.

* Drop old PoV distribution.

* WIP: Fetch PoV directly from backing.

* Backing compiles.

* Runtime access and connection management for PoV distribution.

* Get rid of seemingly dead code.

* Implement PoV fetching.

Backing does not yet use it.

* Don't send `ConnectToValidators` for empty list.

* Even better - no need to check over and over again.

* PoV fetching implemented.

+ Typechecks
+ Should work

Missing:

- Guide
- Tests
- Do fallback fetching in case fetching from seconding validator fails.

* Check PoV hash upon reception.

* Implement retry of PoV fetching in backing.

* Avoid pointless validation spawning.

* Add jaeger span to pov requesting.

* Add back tracing.

* Review remarks.

* Whitespace.

* Whitespace again.

* Cleanup + fix tests.

* Log to log target in overseer.

* Fix more tests.

* Don't fail if group cannot be found.

* Simple test for PoV fetcher.

* Handle missing group membership better.

* Add test for retry functionality.

* Fix flaky test.

* Spaces again.

* Guide updates.

* Spaces.

polkadot/node/network/availability-distribution/src/requester/mod.rs

@@ -39,7 +39,7 @@ use polkadot_subsystem::{
 };
 
 use super::{error::recv_runtime, session_cache::SessionCache, LOG_TARGET, Metrics};
-use crate::error::NonFatalError;
+use crate::error::Error;
 
 /// A task fetching a particular chunk.
 mod fetch_task;
@@ -96,7 +96,7 @@ impl Requester {
 		&mut self,
 		ctx: &mut Context,
 		update: ActiveLeavesUpdate,
-	) -> super::Result<Option<NonFatalError>>
+	) -> super::Result<()>
 	where
 		Context: SubsystemContext,
 	{
@@ -111,9 +111,9 @@ impl Requester {
 		} = update;
 		// Order important! We need to handle activated, prior to deactivated, otherwise we might
 		// cancel still needed jobs.
-		let err = self.start_requesting_chunks(ctx, activated.into_iter()).await?;
+		self.start_requesting_chunks(ctx, activated.into_iter()).await?;
 		self.stop_requesting_chunks(deactivated.into_iter());
-		Ok(err)
+		Ok(())
 	}
 
 	/// Start requesting chunks for newly imported heads.
@@ -121,25 +121,20 @@ impl Requester {
 		&mut self,
 		ctx: &mut Context,
 		new_heads: impl Iterator<Item = ActivatedLeaf>,
-	) -> super::Result<Option<NonFatalError>>
+	) -> super::Result<()>
 	where
 		Context: SubsystemContext,
 	{
 		for ActivatedLeaf { hash: leaf, .. } in new_heads {
-			let cores = match query_occupied_cores(ctx, leaf).await {
-				Err(err) => return Ok(Some(err)),
-				Ok(cores) => cores,
-			};
+			let cores = query_occupied_cores(ctx, leaf).await?;
 			tracing::trace!(
 				target: LOG_TARGET,
 				occupied_cores = ?cores,
 				"Query occupied core"
 			);
-			if let Some(err) = self.add_cores(ctx, leaf, cores).await? {
-				return Ok(Some(err));
-			}
+			self.add_cores(ctx, leaf, cores).await?;
 		}
-		Ok(None)
+		Ok(())
 	}
 
 	/// Stop requesting chunks for obsolete heads.
@@ -164,7 +159,7 @@ impl Requester {
 		ctx: &mut Context,
 		leaf: Hash,
 		cores: impl IntoIterator<Item = OccupiedCore>,
-	) -> super::Result<Option<NonFatalError>>
+	) -> super::Result<()>
 	where
 		Context: SubsystemContext,
 	{
@@ -179,7 +174,7 @@ impl Requester {
 					let tx = self.tx.clone();
 					let metrics = self.metrics.clone();
 
-					let task_cfg = match self
+					let task_cfg = self
 						.session_cache
 						.with_session_info(
 							ctx,
@@ -189,11 +184,7 @@ impl Requester {
 							leaf,
 							|info| FetchTaskConfig::new(leaf, &core, tx, metrics, info),
 						)
-						.await
-					{
-						Err(err) => return Ok(Some(err)),
-						Ok(task_cfg) => task_cfg,
-					};
+						.await?;
 
 					if let Some(task_cfg) = task_cfg {
 						e.insert(FetchTask::start(task_cfg, ctx).await?);
@@ -202,7 +193,7 @@ impl Requester {
 				}
 			}
 		}
-		Ok(None)
+		Ok(())
 	}
 }
 
@@ -237,7 +228,7 @@ impl Stream for Requester {
 async fn query_occupied_cores<Context>(
 	ctx: &mut Context,
 	relay_parent: Hash,
-) -> Result<Vec<OccupiedCore>, NonFatalError>
+) -> Result<Vec<OccupiedCore>, Error>
 where
 	Context: SubsystemContext,
 {