Expose ClaimQueue via a runtime api and use it in `collation-genera…

…tion` (paritytech#3580)

The PR adds two things:
1. Runtime API exposing the whole claim queue
2. Consumes the API in `collation-generation` to fetch the next
scheduled `ParaEntry` for an occupied core.

Related to paritytech#1797

cumulus/client/relay-chain-minimal-node/src/blockchain_rpc_client.rs

@@ -14,7 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::pin::Pin;
+use std::{
+	collections::{BTreeMap, VecDeque},
+	pin::Pin,
+};
 
 use cumulus_relay_chain_interface::{RelayChainError, RelayChainResult};
 use cumulus_relay_chain_rpc_interface::RelayChainRpcClient;
@@ -25,6 +28,7 @@ use polkadot_primitives::{
 	async_backing::{AsyncBackingParams, BackingState},
 	slashing,
 	vstaging::{ApprovalVotingParams, NodeFeatures},
+	CoreIndex,
 };
 use sc_authority_discovery::{AuthorityDiscovery, Error as AuthorityDiscoveryError};
 use sc_client_api::AuxStore;
@@ -442,6 +446,13 @@ impl RuntimeApiSubsystemClient for BlockChainRpcClient {
 	async fn node_features(&self, at: Hash) -> Result<NodeFeatures, ApiError> {
 		Ok(self.rpc_client.parachain_host_node_features(at).await?)
 	}
+
+	async fn claim_queue(
+		&self,
+		at: Hash,
+	) -> Result<BTreeMap<CoreIndex, VecDeque<cumulus_primitives_core::ParaId>>, ApiError> {
+		Ok(self.rpc_client.parachain_host_claim_queue(at).await?)
+	}
 }
 
 #[async_trait::async_trait]

cumulus/client/relay-chain-rpc-interface/src/rpc_client.rs

@@ -24,6 +24,7 @@ use jsonrpsee::{
 };
 use serde::de::DeserializeOwned;
 use serde_json::Value as JsonValue;
+use std::collections::VecDeque;
 use tokio::sync::mpsc::Sender as TokioSender;
 
 use parity_scale_codec::{Decode, Encode};
@@ -34,10 +35,10 @@ use cumulus_primitives_core::{
 		slashing,
 		vstaging::{ApprovalVotingParams, NodeFeatures},
 		BlockNumber, CandidateCommitments, CandidateEvent, CandidateHash,
-		CommittedCandidateReceipt, CoreState, DisputeState, ExecutorParams, GroupRotationInfo,
-		Hash as RelayHash, Header as RelayHeader, InboundHrmpMessage, OccupiedCoreAssumption,
-		PvfCheckStatement, ScrapedOnChainVotes, SessionIndex, SessionInfo, ValidationCode,
-		ValidationCodeHash, ValidatorId, ValidatorIndex, ValidatorSignature,
+		CommittedCandidateReceipt, CoreIndex, CoreState, DisputeState, ExecutorParams,
+		GroupRotationInfo, Hash as RelayHash, Header as RelayHeader, InboundHrmpMessage,
+		OccupiedCoreAssumption, PvfCheckStatement, ScrapedOnChainVotes, SessionIndex, SessionInfo,
+		ValidationCode, ValidationCodeHash, ValidatorId, ValidatorIndex, ValidatorSignature,
 	},
 	InboundDownwardMessage, ParaId, PersistedValidationData,
 };
@@ -647,6 +648,14 @@ impl RelayChainRpcClient {
 			.await
 	}
 
+	pub async fn parachain_host_claim_queue(
+		&self,
+		at: RelayHash,
+	) -> Result<BTreeMap<CoreIndex, VecDeque<ParaId>>, RelayChainError> {
+		self.call_remote_runtime_function("ParachainHost_claim_queue", at, None::<()>)
+			.await
+	}
+
 	pub async fn validation_code_hash(
 		&self,
 		at: RelayHash,

polkadot/node/collation-generation/Cargo.toml

@@ -26,4 +26,5 @@ parity-scale-codec = { version = "3.6.1", default-features = false, features = [
 polkadot-node-subsystem-test-helpers = { path = "../subsystem-test-helpers" }
 test-helpers = { package = "polkadot-primitives-test-helpers", path = "../../primitives/test-helpers" }
 assert_matches = "1.4.0"
+rstest = "0.18.2"
 sp-keyring = { path = "../../../substrate/primitives/keyring" }

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

@@ -38,21 +38,25 @@ use polkadot_node_primitives::{
 	SubmitCollationParams,
 };
 use polkadot_node_subsystem::{
-	messages::{CollationGenerationMessage, CollatorProtocolMessage},
+	messages::{CollationGenerationMessage, CollatorProtocolMessage, RuntimeApiRequest},
 	overseer, ActiveLeavesUpdate, FromOrchestra, OverseerSignal, RuntimeApiError, SpawnedSubsystem,
 	SubsystemContext, SubsystemError, SubsystemResult,
 };
 use polkadot_node_subsystem_util::{
-	request_async_backing_params, request_availability_cores, request_persisted_validation_data,
-	request_validation_code, request_validation_code_hash, request_validators,
+	has_required_runtime, request_async_backing_params, request_availability_cores,
+	request_claim_queue, request_persisted_validation_data, request_validation_code,
+	request_validation_code_hash, request_validators,
 };
 use polkadot_primitives::{
 	collator_signature_payload, CandidateCommitments, CandidateDescriptor, CandidateReceipt,
-	CollatorPair, CoreState, Hash, Id as ParaId, OccupiedCoreAssumption, PersistedValidationData,
-	ValidationCodeHash,
+	CollatorPair, CoreIndex, CoreState, Hash, Id as ParaId, OccupiedCoreAssumption,
+	PersistedValidationData, ScheduledCore, ValidationCodeHash,
 };
 use sp_core::crypto::Pair;
-use std::sync::Arc;
+use std::{
+	collections::{BTreeMap, VecDeque},
+	sync::Arc,
+};
 
 mod error;
 
@@ -223,6 +227,7 @@ async fn handle_new_activations<Context>(
 		let availability_cores = availability_cores??;
 		let n_validators = validators??.len();
 		let async_backing_params = async_backing_params?.ok();
+		let maybe_claim_queue = fetch_claim_queue(ctx.sender(), relay_parent).await?;
 
 		for (core_idx, core) in availability_cores.into_iter().enumerate() {
 			let _availability_core_timer = metrics.time_new_activations_availability_core();
@@ -239,10 +244,25 @@ async fn handle_new_activations<Context>(
 						// TODO [now]: this assumes that next up == current.
 						// in practice we should only set `OccupiedCoreAssumption::Included`
 						// when the candidate occupying the core is also of the same para.
-						if let Some(scheduled) = occupied_core.next_up_on_available {
-							(scheduled, OccupiedCoreAssumption::Included)
-						} else {
-							continue
+						let res = match maybe_claim_queue {
+							Some(ref claim_queue) => {
+								// read what's in the claim queue for this core
+								fetch_next_scheduled_on_core(
+									claim_queue,
+									CoreIndex(core_idx as u32),
+								)
+							},
+							None => {
+								// Runtime doesn't support claim queue runtime api. Fallback to
+								// `next_up_on_available`
+								occupied_core.next_up_on_available
+							},
+						}
+						.map(|scheduled| (scheduled, OccupiedCoreAssumption::Included));
+
+						match res {
+							Some(res) => res,
+							None => continue,
 						}
 					},
 					_ => {
@@ -600,3 +620,37 @@ fn erasure_root(
 	let chunks = polkadot_erasure_coding::obtain_chunks_v1(n_validators, &available_data)?;
 	Ok(polkadot_erasure_coding::branches(&chunks).root())
 }
+
+// Checks if the runtime supports `request_claim_queue` and executes it. Returns `Ok(None)`
+// otherwise. Any [`RuntimeApiError`]s are bubbled up to the caller.
+async fn fetch_claim_queue(
+	sender: &mut impl overseer::CollationGenerationSenderTrait,
+	relay_parent: Hash,
+) -> crate::error::Result<Option<BTreeMap<CoreIndex, VecDeque<ParaId>>>> {
+	if has_required_runtime(
+		sender,
+		relay_parent,
+		RuntimeApiRequest::CLAIM_QUEUE_RUNTIME_REQUIREMENT,
+	)
+	.await
+	{
+		let res = request_claim_queue(relay_parent, sender).await.await??;
+		Ok(Some(res))
+	} else {
+		gum::trace!(target: LOG_TARGET, "Runtime doesn't support `request_claim_queue`");
+		Ok(None)
+	}
+}
+
+// Returns the next scheduled `ParaId` for a core in the claim queue, wrapped in `ScheduledCore`.
+// This function is supposed to be used in `handle_new_activations` hence the return type.
+fn fetch_next_scheduled_on_core(
+	claim_queue: &BTreeMap<CoreIndex, VecDeque<ParaId>>,
+	core_idx: CoreIndex,
+) -> Option<ScheduledCore> {
+	claim_queue
+		.get(&core_idx)?
+		.front()
+		.cloned()
+		.map(|para_id| ScheduledCore { para_id, collator: None })
+}