collation-generation + collator-protocol: collate on multiple assigned cores

polkadot/node/collation-generation/src/lib.rs

@@ -305,7 +305,8 @@ async fn handle_new_activations<Context>(
 
 		let para_backing_state =
 			request_para_backing_state(relay_parent, config.para_id, ctx.sender())
-				.await.await??
+				.await
+				.await??
 				.ok_or(crate::error::Error::MissingParaBackingState)?;
 
 		// We are being very optimistic here, but one of the cores could pend availability some more

polkadot/node/network/collator-protocol/src/collator_side/mod.rs

@@ -748,13 +748,20 @@ async fn advertise_collation<Context>(
 			}
 		}
 
-		let should_advertise = per_relay_parent
-			.validator_group
-			.get(&core_index)
-			.map_or(ShouldAdvertiseTo::NotAuthority, |group| {
-				group.should_advertise_to(candidate_hash, peer_ids, &peer)
-			});
+		let validator_group =
+			if let Some(validator_group) = per_relay_parent.validator_group.get_mut(&core_index) {
+				validator_group
+			} else {
+				gum::debug!(
+					target: LOG_TARGET,
+					?relay_parent,
+					?core_index,
+					"Skipping advertising to validator, validator group for core not found",
+				);
+				return
+			};
 
+		let should_advertise = validator_group.should_advertise_to(candidate_hash, peer_ids, &peer);
 		match should_advertise {
 			ShouldAdvertiseTo::Yes => {},
 			ShouldAdvertiseTo::NotAuthority | ShouldAdvertiseTo::AlreadyAdvertised => {
@@ -802,11 +809,7 @@ async fn advertise_collation<Context>(
 		))
 		.await;
 
-		per_relay_parent
-			.validator_group
-			.get_mut(&core_index)
-			.expect("should_advertise returned `ShouldAdvertiseTo::Yes` above; qed")
-			.advertised_to_peer(candidate_hash, &peer_ids, peer);
+		validator_group.advertised_to_peer(candidate_hash, &peer_ids, peer);
 
 		advertisement_timeouts.push(ResetInterestTimeout::new(
 			*candidate_hash,

prdoc/pr_3795.prdoc

@@ -0,0 +1,14 @@
+title: Enable collators to build on multiple cores
+
+doc:
+  - audience: Node Dev
+    description: |
+      Introduces a `CoreIndex` parameter in `SubmitCollationParams`. This enables
+      the collators to make use of potentially multiple cores assigned at some relay
+      chain block. This extra parameter is used by the collator protocol and collation
+      generation subsystems to forward the collation to the approapriate backing group.
+
+crates:
+- name: polkadot-node-collation-generation
+- name: polkadot-collator-protocol
+  bump: minor