Add candidate info to OccupiedCore (#2134)

* guide: add candidate information to OccupiedCore

* add descriptor and hash to occupied core type

* guide: add candidate hash to inclusion

* runtime: return candidate info in core state

* bitfield signing: stop querying runtime as much

* minimize going to runtime in availability distribution

* fix availability distribution tests

* guide: remove para ID from Occupied core

* get all crates compiling

polkadot/node/core/bitfield-signing/src/lib.rs

@@ -78,37 +78,7 @@ async fn get_core_availability(
 ) -> Result<bool, Error> {
 	let span = jaeger::hash_span(&relay_parent, "core-availability");
 	if let CoreState::Occupied(core) = core {
-		tracing::trace!(target: LOG_TARGET, para_id = %core.para_id, "Getting core availability");
-
-		let _span = span.child("occupied");
-		let (tx, rx) = oneshot::channel();
-		sender
-			.lock()
-			.await
-			.send(
-				AllMessages::from(RuntimeApiMessage::Request(
-					relay_parent,
-					RuntimeApiRequest::CandidatePendingAvailability(core.para_id, tx),
-				)).into(),
-			)
-			.await?;
-
-		let committed_candidate_receipt = match rx.await? {
-			Ok(Some(ccr)) => ccr,
-			Ok(None) => {
-				tracing::trace!(target: LOG_TARGET, para_id = %core.para_id, "No committed candidate");
-				return Ok(false)
-			},
-			Err(e) => {
-				// Don't take down the node on runtime API errors.
-				tracing::warn!(target: LOG_TARGET, err = ?e, "Encountered a runtime API error");
-				return Ok(false);
-			}
-		};
-
-		drop(_span);
 		let _span = span.child("query chunk");
-		let candidate_hash = committed_candidate_receipt.hash();
 
 		let (tx, rx) = oneshot::channel();
 		sender
@@ -116,7 +86,7 @@ async fn get_core_availability(
 			.await
 			.send(
 				AllMessages::from(AvailabilityStoreMessage::QueryChunkAvailability(
-					candidate_hash,
+					core.candidate_hash,
 					validator_idx,
 					tx,
 				)).into(),
@@ -127,9 +97,9 @@ async fn get_core_availability(
 
 		tracing::trace!(
 			target: LOG_TARGET,
-			para_id = %core.para_id,
+			para_id = %core.para_id(),
 			availability = ?res,
-			?candidate_hash,
+			?core.candidate_hash,
 			"Candidate availability",
 		);
 
@@ -325,17 +295,18 @@ pub type BitfieldSigningSubsystem<Spawner, Context> = JobManager<Spawner, Contex
 mod tests {
 	use super::*;
 	use futures::{pin_mut, executor::block_on};
-	use polkadot_primitives::v1::OccupiedCore;
+	use polkadot_primitives::v1::{CandidateHash, OccupiedCore};
 
-	fn occupied_core(para_id: u32) -> CoreState {
+	fn occupied_core(para_id: u32, candidate_hash: CandidateHash) -> CoreState {
 		CoreState::Occupied(OccupiedCore {
-			para_id: para_id.into(),
 			group_responsible: para_id.into(),
 			next_up_on_available: None,
 			occupied_since: 100_u32,
 			time_out_at: 200_u32,
 			next_up_on_time_out: None,
 			availability: Default::default(),
+			candidate_hash,
+			candidate_descriptor: Default::default(),
 		})
 	}
 
@@ -354,6 +325,9 @@ mod tests {
 			).fuse();
 			pin_mut!(future);
 
+			let hash_a = CandidateHash(Hash::repeat_byte(1));
+			let hash_b = CandidateHash(Hash::repeat_byte(2));
+
 			loop {
 				futures::select! {
 					m = receiver.next() => match m.unwrap() {
@@ -363,29 +337,16 @@ mod tests {
 							),
 						) => {
 							assert_eq!(relay_parent, rp);
-							tx.send(Ok(vec![CoreState::Free, occupied_core(1), occupied_core(2)])).unwrap();
+							tx.send(Ok(vec![CoreState::Free, occupied_core(1, hash_a), occupied_core(2, hash_b)])).unwrap();
-						},
-						FromJobCommand::SendMessage(
-							AllMessages::RuntimeApi(
-								RuntimeApiMessage::Request(rp, RuntimeApiRequest::CandidatePendingAvailability(para_id, tx)),
-							),
-						) => {
-							assert_eq!(relay_parent, rp);
-
-							if para_id == 1.into() {
-								tx.send(Ok(Some(Default::default()))).unwrap();
-							} else {
-								tx.send(Ok(None)).unwrap();
-							}
 						},
 						FromJobCommand::SendMessage(
 							AllMessages::AvailabilityStore(
-								AvailabilityStoreMessage::QueryChunkAvailability(_, vidx, tx),
+								AvailabilityStoreMessage::QueryChunkAvailability(c_hash, vidx, tx),
 							),
 						) => {
 							assert_eq!(validator_index, vidx);
 
-							tx.send(true).unwrap();
+							tx.send(c_hash == hash_a).unwrap();
 						},
 						o => panic!("Unknown message: {:?}", o),
 					},

polkadot/node/core/provisioner/src/tests.rs

@@ -4,13 +4,14 @@ use polkadot_primitives::v1::{OccupiedCore, ScheduledCore};
 
 pub fn occupied_core(para_id: u32) -> CoreState {
 	CoreState::Occupied(OccupiedCore {
-		para_id: para_id.into(),
 		group_responsible: para_id.into(),
 		next_up_on_available: None,
 		occupied_since: 100_u32,
 		time_out_at: 200_u32,
 		next_up_on_time_out: None,
 		availability: bitvec![bitvec::order::Lsb0, u8; 0; 32],
+		candidate_descriptor: Default::default(),
+		candidate_hash: Default::default(),
 	})
 }
 

polkadot/node/network/availability-distribution/src/lib.rs

@@ -36,7 +36,7 @@ use polkadot_node_network_protocol::{
 };
 use polkadot_node_subsystem_util::metrics::{self, prometheus};
 use polkadot_primitives::v1::{
-	BlakeTwo256, CommittedCandidateReceipt, CoreState, ErasureChunk, Hash, HashT, Id as ParaId,
+	BlakeTwo256, CoreState, ErasureChunk, Hash, HashT,
 	SessionIndex, ValidatorId, ValidatorIndex, PARACHAIN_KEY_TYPE_ID, CandidateHash,
 	CandidateDescriptor,
 };
@@ -62,11 +62,6 @@ const LOG_TARGET: &'static str = "availability_distribution";
 
 #[derive(Debug, Error)]
 enum Error {
-	#[error("Response channel to obtain PendingAvailability failed")]
-	QueryPendingAvailabilityResponseChannel(#[source] oneshot::Canceled),
-	#[error("RuntimeAPI to obtain PendingAvailability failed")]
-	QueryPendingAvailability(#[source] RuntimeApiError),
-
 	#[error("Response channel to obtain StoreChunk failed")]
 	StoreChunkResponseChannel(#[source] oneshot::Canceled),
 
@@ -795,19 +790,12 @@ where
 			e => e.or_default(),
 		};
 
-		for para in query_para_ids(ctx, relay_parent).await? {
+		for (receipt_hash, descriptor) in query_pending_availability(ctx, relay_parent).await? {
-			if let Some(ccr) = query_pending_availability(ctx, relay_parent, para).await? {
+			// unfortunately we have no good way of telling the candidate was
-				let receipt_hash = ccr.hash();
+			// cached until now. But we don't clobber a `Cached` entry if there
-				let descriptor = ccr.descriptor().clone();
+			// is one already.
-
+			live_candidates.entry(receipt_hash).or_insert(FetchedLiveCandidate::Fresh(descriptor));
-				// unfortunately we have no good way of telling the candidate was
+			receipts_for.insert(receipt_hash);
-				// cached until now. But we don't clobber a `Cached` entry if there
-				// is one already.
-				live_candidates.entry(receipt_hash)
-					.or_insert(FetchedLiveCandidate::Fresh(descriptor));
-
-				receipts_for.insert(receipt_hash);
-			}
 		}
 	}
 
@@ -850,9 +838,10 @@ where
 	Ok((live_candidates, ancestors))
 }
 
-/// Query all para IDs that are occupied under a given relay-parent.
+/// Query all hashes and descriptors of candidates pending availability at a particular block.
 #[tracing::instrument(level = "trace", skip(ctx), fields(subsystem = LOG_TARGET))]
-async fn query_para_ids<Context>(ctx: &mut Context, relay_parent: Hash) -> Result<Vec<ParaId>>
+async fn query_pending_availability<Context>(ctx: &mut Context, relay_parent: Hash)
+	-> Result<Vec<(CandidateHash, CandidateDescriptor)>>
 where
 	Context: SubsystemContext<Message = AvailabilityDistributionMessage>,
 {
@@ -863,22 +852,18 @@ where
 	)))
 	.await;
 
-	let all_para_ids = rx
+	let cores: Vec<_> = rx
 		.await
 		.map_err(|e| Error::AvailabilityCoresResponseChannel(e))?
 		.map_err(|e| Error::AvailabilityCores(e))?;
 
-	let occupied_para_ids = all_para_ids
+	Ok(cores.into_iter()
-		.into_iter()
+		.filter_map(|core_state| if let CoreState::Occupied(occupied) = core_state {
-		.filter_map(|core_state| {
+			Some((occupied.candidate_hash, occupied.candidate_descriptor))
-			if let CoreState::Occupied(occupied) = core_state {
+		} else {
-				Some(occupied.para_id)
+			None
-			} else {
-				None
-			}
 		})
-		.collect();
+		.collect())
-	Ok(occupied_para_ids)
 }
 
 /// Modify the reputation of a peer based on its behavior.
@@ -954,27 +939,6 @@ where
 	rx.await.map_err(|e| Error::StoreChunkResponseChannel(e))
 }
 
-/// Request the head data for a particular para.
-#[tracing::instrument(level = "trace", skip(ctx), fields(subsystem = LOG_TARGET))]
-async fn query_pending_availability<Context>(
-	ctx: &mut Context,
-	relay_parent: Hash,
-	para: ParaId,
-) -> Result<Option<CommittedCandidateReceipt>>
-where
-	Context: SubsystemContext<Message = AvailabilityDistributionMessage>,
-{
-	let (tx, rx) = oneshot::channel();
-	ctx.send_message(AllMessages::RuntimeApi(RuntimeApiMessage::Request(
-		relay_parent,
-		RuntimeApiRequest::CandidatePendingAvailability(para, tx),
-	))).await;
-
-	rx.await
-		.map_err(|e| Error::QueryPendingAvailabilityResponseChannel(e))?
-		.map_err(|e| Error::QueryPendingAvailability(e))
-}
-
 /// Query the validator set.
 #[tracing::instrument(level = "trace", skip(ctx), fields(subsystem = LOG_TARGET))]
 async fn query_validators<Context>(

polkadot/node/network/availability-distribution/src/tests.rs

@@ -21,7 +21,8 @@ use polkadot_node_network_protocol::{view, ObservedRole};
 use polkadot_node_subsystem_util::TimeoutExt;
 use polkadot_primitives::v1::{
 	AvailableData, BlockData, CandidateCommitments, CandidateDescriptor, GroupIndex,
-	GroupRotationInfo, HeadData, OccupiedCore, PersistedValidationData, PoV, ScheduledCore,
+	GroupRotationInfo, HeadData, OccupiedCore, PersistedValidationData, PoV, ScheduledCore, Id as ParaId,
+	CommittedCandidateReceipt,
 };
 use polkadot_subsystem_testhelpers as test_helpers;
 
@@ -29,6 +30,7 @@ use futures::{executor, future, Future};
 use sc_keystore::LocalKeystore;
 use sp_application_crypto::AppKey;
 use sp_keystore::{SyncCryptoStore, SyncCryptoStorePtr};
+use sp_keyring::Sr25519Keyring;
 use std::{sync::Arc, time::Duration};
 use maplit::hashmap;
 
@@ -95,20 +97,19 @@ async fn overseer_recv(
 	msg
 }
 
-fn dummy_occupied_core(para: ParaId) -> CoreState {
+fn occupied_core_from_candidate(receipt: &CommittedCandidateReceipt) -> CoreState {
 	CoreState::Occupied(OccupiedCore {
-		para_id: para,
 		next_up_on_available: None,
 		occupied_since: 0,
 		time_out_at: 5,
 		next_up_on_time_out: None,
 		availability: Default::default(),
 		group_responsible: GroupIndex::from(0),
+		candidate_hash: receipt.hash(),
+		candidate_descriptor: receipt.descriptor().clone(),
 	})
 }
 
-use sp_keyring::Sr25519Keyring;
-
 #[derive(Clone)]
 struct TestState {
 	chain_ids: Vec<ParaId>,
@@ -388,7 +389,6 @@ async fn change_our_view(
 	ancestors: Vec<Hash>,
 	session_per_relay_parent: HashMap<Hash, SessionIndex>,
 	availability_cores_per_relay_parent: HashMap<Hash, Vec<CoreState>>,
-	candidate_pending_availabilities_per_relay_parent: HashMap<Hash, Vec<CommittedCandidateReceipt>>,
 	data_availability: HashMap<CandidateHash, bool>,
 	chunk_data_per_candidate: HashMap<CandidateHash, (PoV, PersistedValidationData)>,
 	send_chunks_to: HashMap<CandidateHash, Vec<PeerId>>,
@@ -436,7 +436,7 @@ async fn change_our_view(
 	}
 
 	for _ in 0..availability_cores_per_relay_parent.len() {
-		let relay_parent = assert_matches!(
+		assert_matches!(
 			overseer_recv(virtual_overseer).await,
 			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
 				relay_parent,
@@ -446,30 +446,8 @@ async fn change_our_view(
 					.expect(&format!("Availability core for relay parent {:?} does not exist", relay_parent));
 
 				tx.send(Ok(cores.clone())).unwrap();
-				relay_parent
 			}
 		);
-
-		let pending_availability = candidate_pending_availabilities_per_relay_parent.get(&relay_parent)
-			.expect(&format!("Candidate pending availability for relay parent {:?} does not exist", relay_parent));
-
-		for _ in 0..pending_availability.len() {
-			assert_matches!(
-				overseer_recv(virtual_overseer).await,
-				AllMessages::RuntimeApi(RuntimeApiMessage::Request(
-					hash,
-					RuntimeApiRequest::CandidatePendingAvailability(para, tx)
-				)) => {
-					assert_eq!(relay_parent, hash);
-
-					let candidate = pending_availability.iter()
-						.find(|c| c.descriptor.para_id == para)
-						.expect(&format!("Pending candidate for para {} does not exist", para));
-
-					tx.send(Ok(Some(candidate.clone()))).unwrap();
-				}
-			);
-		}
 	}
 
 	for _ in 0..data_availability.len() {
@@ -571,7 +549,6 @@ fn check_views() {
 		let mut virtual_overseer = test_harness.virtual_overseer;
 
 		let TestState {
-			chain_ids,
 			validator_public,
 			relay_parent: current,
 			ancestors,
@@ -588,36 +565,37 @@ fn check_views() {
 			vec![ancestors[0], genesis],
 			hashmap! { current => 1, genesis => 1 },
 			hashmap! {
-				ancestors[0] => vec![dummy_occupied_core(chain_ids[0]), dummy_occupied_core(chain_ids[1])],
+				ancestors[0] => vec![
+					occupied_core_from_candidate(&candidates[0]),
+					occupied_core_from_candidate(&candidates[1]),
+				],
 				current => vec![
 					CoreState::Occupied(OccupiedCore {
-						para_id: chain_ids[0].clone(),
 						next_up_on_available: None,
 						occupied_since: 0,
 						time_out_at: 10,
 						next_up_on_time_out: None,
 						availability: Default::default(),
 						group_responsible: GroupIndex::from(0),
+						candidate_hash: candidates[0].hash(),
+						candidate_descriptor: candidates[0].descriptor().clone(),
 					}),
 					CoreState::Free,
 					CoreState::Free,
 					CoreState::Occupied(OccupiedCore {
-						para_id: chain_ids[1].clone(),
 						next_up_on_available: None,
 						occupied_since: 1,
 						time_out_at: 7,
 						next_up_on_time_out: None,
 						availability: Default::default(),
 						group_responsible: GroupIndex::from(0),
+						candidate_hash: candidates[1].hash(),
+						candidate_descriptor: candidates[1].descriptor().clone(),
 					}),
 					CoreState::Free,
 					CoreState::Free,
 				]
 			},
-			hashmap! {
-				ancestors[0] => vec![candidates[0].clone(), candidates[1].clone()],
-				current => vec![candidates[0].clone(), candidates[1].clone()],
-			},
 			hashmap! {
 				candidates[0].hash() => true,
 				candidates[1].hash() => false,
@@ -690,11 +668,10 @@ fn reputation_verification() {
 			hashmap! { current => 1 },
 			hashmap! {
 				current => vec![
-					dummy_occupied_core(candidates[0].descriptor.para_id),
+					occupied_core_from_candidate(&candidates[0]),
-					dummy_occupied_core(candidates[1].descriptor.para_id)
+					occupied_core_from_candidate(&candidates[1]),
 				],
 			},
-			hashmap! { current => vec![candidates[0].clone(), candidates[1].clone()] },
 			hashmap! { candidates[0].hash() => true, candidates[1].hash() => false },
 			hashmap! { candidates[0].hash() => (pov_blocks[0].clone(), test_state.persisted_validation_data.clone())},
 			hashmap! {},
@@ -783,10 +760,9 @@ fn not_a_live_candidate_is_detected() {
 			hashmap! { current => 1 },
 			hashmap! {
 				current => vec![
-					dummy_occupied_core(candidates[0].descriptor.para_id),
+					occupied_core_from_candidate(&candidates[0]),
 				],
 			},
-			hashmap! { current => vec![candidates[0].clone()] },
 			hashmap! { candidates[0].hash() => true },
 			hashmap! { candidates[0].hash() => (pov_blocks[0].clone(), test_state.persisted_validation_data.clone())},
 			hashmap! {},
@@ -832,10 +808,9 @@ fn peer_change_view_before_us() {
 			hashmap! { current => 1 },
 			hashmap! {
 				current => vec![
-					dummy_occupied_core(candidates[0].descriptor.para_id),
+					occupied_core_from_candidate(&candidates[0]),
 				],
 			},
-			hashmap! { current => vec![candidates[0].clone()] },
 			hashmap! { candidates[0].hash() => true },
 			hashmap! { candidates[0].hash() => (pov_blocks[0].clone(), test_state.persisted_validation_data.clone())},
 			hashmap! { candidates[0].hash() => vec![peer_a.clone()] },
@@ -880,10 +855,9 @@ fn candidate_chunks_are_put_into_message_vault_when_candidate_is_first_seen() {
 			hashmap! { ancestors[0] => 1 },
 			hashmap! {
 				ancestors[0] => vec![
-					dummy_occupied_core(candidates[0].descriptor.para_id),
+					occupied_core_from_candidate(&candidates[0]),
 				],
 			},
-			hashmap! { ancestors[0] => vec![candidates[0].clone()] },
 			hashmap! { candidates[0].hash() => true },
 			hashmap! { candidates[0].hash() => (pov_blocks[0].clone(), test_state.persisted_validation_data.clone())},
 			hashmap! {},
@@ -897,10 +871,9 @@ fn candidate_chunks_are_put_into_message_vault_when_candidate_is_first_seen() {
 			hashmap! { current => 1 },
 			hashmap! {
 				current => vec![
-					dummy_occupied_core(candidates[0].descriptor.para_id),
+					occupied_core_from_candidate(&candidates[0]),
 				],
 			},
-			hashmap! { current => vec![candidates[0].clone()] },
 			hashmap! { candidates[0].hash() => true },
 			hashmap! {},
 			hashmap! {},
@@ -1168,50 +1141,28 @@ fn query_pending_availability_at_pulls_from_and_updates_receipts() {
 			) if r == hash_b => {
 				let _ = tx.send(Ok(vec![
 					CoreState::Occupied(OccupiedCore {
-						para_id: para_b,
 						next_up_on_available: None,
 						occupied_since: 0,
 						time_out_at: 0,
 						next_up_on_time_out: None,
 						availability: Default::default(),
 						group_responsible: GroupIndex::from(0),
+						candidate_hash: candidate_hash_b,
+						candidate_descriptor: candidate_b.descriptor.clone(),
 					}),
 					CoreState::Occupied(OccupiedCore {
-						para_id: para_c,
 						next_up_on_available: None,
 						occupied_since: 0,
 						time_out_at: 0,
 						next_up_on_time_out: None,
 						availability: Default::default(),
 						group_responsible: GroupIndex::from(0),
+						candidate_hash: candidate_hash_c,
+						candidate_descriptor: candidate_c.descriptor.clone(),
 					}),
 				]));
 			}
 		);
-
-		assert_matches!(
-			overseer_recv(&mut virtual_overseer).await,
-			AllMessages::RuntimeApi(
-				RuntimeApiMessage::Request(
-					r,
-					RuntimeApiRequest::CandidatePendingAvailability(p, tx),
-				)
-			) if r == hash_b && p == para_b => {
-				let _ = tx.send(Ok(Some(candidate_b)));
-			}
-		);
-
-		assert_matches!(
-			overseer_recv(&mut virtual_overseer).await,
-			AllMessages::RuntimeApi(
-				RuntimeApiMessage::Request(
-					r,
-					RuntimeApiRequest::CandidatePendingAvailability(p, tx),
-				)
-			) if r == hash_b && p == para_c => {
-				let _ = tx.send(Ok(Some(candidate_c)));
-			}
-		);
 	};
 
 	futures::pin_mut!(test_fut);
@@ -1256,11 +1207,10 @@ fn new_peer_gets_all_chunks_send() {
 			hashmap! { current => 1 },
 			hashmap! {
 				current => vec![
-					dummy_occupied_core(candidates[0].descriptor.para_id),
+					occupied_core_from_candidate(&candidates[0]),
-					dummy_occupied_core(candidates[1].descriptor.para_id)
+					occupied_core_from_candidate(&candidates[1])
 				],
 			},
-			hashmap! { current => vec![candidates[0].clone(), candidates[1].clone()] },
 			hashmap! { candidates[0].hash() => true, candidates[1].hash() => false },
 			hashmap! { candidates[0].hash() => (pov_blocks[0].clone(), test_state.persisted_validation_data.clone())},
 			hashmap! {},

polkadot/primitives/src/v1.rs

@@ -576,11 +576,11 @@ impl<N: Saturating + BaseArithmetic + Copy> GroupRotationInfo<N> {
 }
 
 /// Information about a core which is currently occupied.
-#[derive(Clone, Encode, Decode, Debug)]
+#[derive(Clone, Encode, Decode)]
-#[cfg_attr(feature = "std", derive(PartialEq))]
+#[cfg_attr(feature = "std", derive(Debug, PartialEq))]
-pub struct OccupiedCore<N = BlockNumber> {
+pub struct OccupiedCore<H = Hash, N = BlockNumber> {
-	/// The ID of the para occupying the core.
+    // NOTE: this has no ParaId as it can be deduced from the candidate descriptor.
-	pub para_id: Id,
+
 	/// If this core is freed by availability, this is the assignment that is next up on this
 	/// core, if any. None if there is nothing queued for this core.
 	pub next_up_on_available: Option<ScheduledCore>,
@@ -598,11 +598,22 @@ pub struct OccupiedCore<N = BlockNumber> {
 	pub availability: BitVec<bitvec::order::Lsb0, u8>,
 	/// The group assigned to distribute availability pieces of this candidate.
 	pub group_responsible: GroupIndex,
+	/// The hash of the candidate occupying the core.
+	pub candidate_hash: CandidateHash,
+	/// The descriptor of the candidate occupying the core.
+	pub candidate_descriptor: CandidateDescriptor<H>,
+}
+
+impl<H, N> OccupiedCore<H, N> {
+	/// Get the Para currently occupying this core.
+	pub fn para_id(&self) -> Id {
+		self.candidate_descriptor.para_id
+	}
 }
 
 /// Information about a core which is currently occupied.
-#[derive(Clone, Encode, Decode, Debug)]
+#[derive(Clone, Encode, Decode)]
-#[cfg_attr(feature = "std", derive(PartialEq, Default))]
+#[cfg_attr(feature = "std", derive(Debug, PartialEq, Default))]
 pub struct ScheduledCore {
 	/// The ID of a para scheduled.
 	pub para_id: Id,
@@ -611,12 +622,12 @@ pub struct ScheduledCore {
 }
 
 /// The state of a particular availability core.
-#[derive(Clone, Encode, Decode, Debug)]
+#[derive(Clone, Encode, Decode)]
-#[cfg_attr(feature = "std", derive(PartialEq))]
+#[cfg_attr(feature = "std", derive(Debug, PartialEq))]
-pub enum CoreState<N = BlockNumber> {
+pub enum CoreState<H = Hash, N = BlockNumber> {
 	/// The core is currently occupied.
 	#[codec(index = "0")]
-	Occupied(OccupiedCore<N>),
+	Occupied(OccupiedCore<H, N>),
 	/// The core is currently free, with a para scheduled and given the opportunity
 	/// to occupy.
 	///
@@ -634,7 +645,7 @@ impl<N> CoreState<N> {
 	/// If this core state has a `para_id`, return it.
 	pub fn para_id(&self) -> Option<Id> {
 		match self {
-			Self::Occupied(OccupiedCore { para_id, ..}) => Some(*para_id),
+			Self::Occupied(ref core) => Some(core.para_id()),
 			Self::Scheduled(ScheduledCore { para_id, .. }) => Some(*para_id),
 			Self::Free => None,
 		}
@@ -718,7 +729,7 @@ sp_api::decl_runtime_apis! {
 
 		/// Yields information on all availability cores. Cores are either free or occupied. Free
 		/// cores can have paras assigned to them.
-		fn availability_cores() -> Vec<CoreState<N>>;
+		fn availability_cores() -> Vec<CoreState<H, N>>;
 
 		/// Yields the full validation data for the given ParaId along with an assumption that
 		/// should be used if the para currently occupieds a core.

polkadot/roadmap/implementers-guide/src/node/availability/bitfield-signing.md

@@ -24,6 +24,6 @@ If not running as a validator, do nothing.
 
 - Begin by waiting a fixed period of time so availability distribution has the chance to make candidates available.
 - Determine our validator index `i`, the set of backed candidates pending availability in `r`, and which bit of the bitfield each corresponds to.
-- Start with an empty bitfield. For each bit in the bitfield, if there is a candidate pending availability, query the [Availability Store](../utility/availability-store.md) for whether we have the availability chunk for our validator index.
+- Start with an empty bitfield. For each bit in the bitfield, if there is a candidate pending availability, query the [Availability Store](../utility/availability-store.md) for whether we have the availability chunk for our validator index. The `OccupiedCore` struct contains the candidate hash so the full candidate does not need to be fetched from runtime.
 - For all chunks we have, set the corresponding bit in the bitfield.
 - Sign the bitfield and dispatch a `BitfieldDistribution::DistributeBitfield` message.

polkadot/roadmap/implementers-guide/src/runtime-api/availability-cores.md

@@ -12,8 +12,7 @@ This is all the information that a validator needs about scheduling for the curr
 
 ```rust
 struct OccupiedCore {
-    /// The ID of the para occupying the core.
+    // NOTE: this has no ParaId as it can be deduced from the candidate descriptor.
-    para_id: ParaId,
     /// If this core is freed by availability, this is the assignment that is next up on this
     /// core, if any. None if there is nothing queued for this core.
     next_up_on_available: Option<ScheduledCore>,
@@ -31,6 +30,10 @@ struct OccupiedCore {
     availability: Bitfield,
     /// The group assigned to distribute availability pieces of this candidate.
     group_responsible: GroupIndex,
+    /// The hash of the candidate occupying the core.
+    candidate_hash: CandidateHash,
+    /// The descriptor of the candidate occupying the core.
+    candidate_descriptor: CandidateDescriptor,
 }
 
 struct ScheduledCore {

polkadot/roadmap/implementers-guide/src/runtime/inclusion.md

@@ -14,6 +14,7 @@ struct AvailabilityBitfield {
 
 struct CandidatePendingAvailability {
   core: CoreIndex, // availability core
+  hash: CandidateHash,
   descriptor: CandidateDescriptor,
   availability_votes: Bitfield, // one bit per validator.
   relay_parent_number: BlockNumber, // number of the relay-parent.

polkadot/runtime/kusama/src/lib.rs

@@ -1347,7 +1347,7 @@ sp_api::impl_runtime_apis! {
 			(Vec::new(), GroupRotationInfo { session_start_block: 0, group_rotation_frequency: 0, now: 0 })
 		}
 
-		fn availability_cores() -> Vec<CoreState<BlockNumber>> {
+		fn availability_cores() -> Vec<CoreState<Hash, BlockNumber>> {
 			Vec::new()
 		}
 

polkadot/runtime/parachains/src/inclusion.rs

@@ -25,7 +25,7 @@ use primitives::v1::{
 	ValidatorId, CandidateCommitments, CandidateDescriptor, ValidatorIndex, Id as ParaId,
 	AvailabilityBitfield as AvailabilityBitfield, SignedAvailabilityBitfields, SigningContext,
 	BackedCandidate, CoreIndex, GroupIndex, CommittedCandidateReceipt,
-	CandidateReceipt, HeadData,
+	CandidateReceipt, HeadData, CandidateHash,
 };
 use frame_support::{
 	decl_storage, decl_module, decl_error, decl_event, ensure, debug,
@@ -58,6 +58,8 @@ pub struct AvailabilityBitfieldRecord<N> {
 pub struct CandidatePendingAvailability<H, N> {
 	/// The availability core this is assigned to.
 	core: CoreIndex,
+	/// The candidate hash.
+	hash: CandidateHash,
 	/// The candidate descriptor.
 	descriptor: CandidateDescriptor<H>,
 	/// The received availability votes. One bit per validator.
@@ -85,6 +87,16 @@ impl<H, N> CandidatePendingAvailability<H, N> {
 	pub(crate) fn core_occupied(&self)-> CoreIndex {
 		self.core.clone()
 	}
+
+	/// Get the candidate hash.
+	pub(crate) fn candidate_hash(&self) -> CandidateHash {
+		self.hash
+	}
+
+	/// Get the canddiate descriptor.
+	pub(crate) fn candidate_descriptor(&self) -> &CandidateDescriptor<H> {
+		&self.descriptor
+	}
 }
 
 /// A hook for applying validator rewards
@@ -568,6 +580,8 @@ impl<T: Config> Module<T> {
 				candidate.candidate.commitments.head_data.clone(),
 			));
 
+			let candidate_hash = candidate.candidate.hash();
+
 			let (descriptor, commitments) = (
 				candidate.candidate.descriptor,
 				candidate.candidate.commitments,
@@ -575,6 +589,7 @@ impl<T: Config> Module<T> {
 
 			<PendingAvailability<T>>::insert(&para_id, CandidatePendingAvailability {
 				core,
+				hash: candidate_hash,
 				descriptor,
 				availability_votes,
 				relay_parent_number: check_cx.relay_parent_number,
@@ -1112,6 +1127,7 @@ mod tests {
 			let default_candidate = TestCandidateBuilder::default().build();
 			<PendingAvailability<Test>>::insert(chain_a, CandidatePendingAvailability {
 				core: CoreIndex::from(0),
+				hash: default_candidate.hash(),
 				descriptor: default_candidate.descriptor.clone(),
 				availability_votes: default_availability_votes(),
 				relay_parent_number: 0,
@@ -1122,6 +1138,7 @@ mod tests {
 
 			<PendingAvailability<Test>>::insert(&chain_b, CandidatePendingAvailability {
 				core: CoreIndex::from(1),
+				hash: default_candidate.hash(),
 				descriptor: default_candidate.descriptor,
 				availability_votes: default_availability_votes(),
 				relay_parent_number: 0,
@@ -1286,6 +1303,7 @@ mod tests {
 				let default_candidate = TestCandidateBuilder::default().build();
 				<PendingAvailability<Test>>::insert(chain_a, CandidatePendingAvailability {
 					core: CoreIndex::from(0),
+					hash: default_candidate.hash(),
 					descriptor: default_candidate.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: 0,
@@ -1321,6 +1339,7 @@ mod tests {
 				let default_candidate = TestCandidateBuilder::default().build();
 				<PendingAvailability<Test>>::insert(chain_a, CandidatePendingAvailability {
 					core: CoreIndex::from(0),
+					hash: default_candidate.hash(),
 					descriptor: default_candidate.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: 0,
@@ -1393,6 +1412,7 @@ mod tests {
 
 			<PendingAvailability<Test>>::insert(chain_a, CandidatePendingAvailability {
 				core: CoreIndex::from(0),
+				hash: candidate_a.hash(),
 				descriptor: candidate_a.descriptor,
 				availability_votes: default_availability_votes(),
 				relay_parent_number: 0,
@@ -1409,6 +1429,7 @@ mod tests {
 
 			<PendingAvailability<Test>>::insert(chain_b, CandidatePendingAvailability {
 				core: CoreIndex::from(1),
+				hash: candidate_b.hash(),
 				descriptor: candidate_b.descriptor,
 				availability_votes: default_availability_votes(),
 				relay_parent_number: 0,
@@ -1839,6 +1860,7 @@ mod tests {
 				let candidate = TestCandidateBuilder::default().build();
 				<PendingAvailability<Test>>::insert(&chain_a, CandidatePendingAvailability {
 					core: CoreIndex::from(0),
+					hash: candidate.hash(),
 					descriptor: candidate.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: 3,
@@ -2127,6 +2149,7 @@ mod tests {
 				<PendingAvailability<Test>>::get(&chain_a),
 				Some(CandidatePendingAvailability {
 					core: CoreIndex::from(0),
+					hash: candidate_a.hash(),
 					descriptor: candidate_a.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: System::block_number() - 1,
@@ -2143,6 +2166,7 @@ mod tests {
 				<PendingAvailability<Test>>::get(&chain_b),
 				Some(CandidatePendingAvailability {
 					core: CoreIndex::from(1),
+					hash: candidate_b.hash(),
 					descriptor: candidate_b.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: System::block_number() - 1,
@@ -2159,6 +2183,7 @@ mod tests {
 				<PendingAvailability<Test>>::get(&thread_a),
 				Some(CandidatePendingAvailability {
 					core: CoreIndex::from(2),
+					hash: candidate_c.hash(),
 					descriptor: candidate_c.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: System::block_number() - 1,
@@ -2254,6 +2279,7 @@ mod tests {
 				<PendingAvailability<Test>>::get(&chain_a),
 				Some(CandidatePendingAvailability {
 					core: CoreIndex::from(0),
+					hash: candidate_a.hash(),
 					descriptor: candidate_a.descriptor,
 					availability_votes: default_availability_votes(),
 					relay_parent_number: System::block_number() - 1,
@@ -2329,6 +2355,7 @@ mod tests {
 			let candidate = TestCandidateBuilder::default().build();
 			<PendingAvailability<Test>>::insert(&chain_a, CandidatePendingAvailability {
 				core: CoreIndex::from(0),
+				hash: candidate.hash(),
 				descriptor: candidate.descriptor.clone(),
 				availability_votes: default_availability_votes(),
 				relay_parent_number: 5,
@@ -2339,6 +2366,7 @@ mod tests {
 
 			<PendingAvailability<Test>>::insert(&chain_b, CandidatePendingAvailability {
 				core: CoreIndex::from(1),
+				hash: candidate.hash(),
 				descriptor: candidate.descriptor,
 				availability_votes: default_availability_votes(),
 				relay_parent_number: 6,

polkadot/runtime/parachains/src/runtime_api_impl/v1.rs

@@ -46,7 +46,7 @@ pub fn validator_groups<T: initializer::Config>() -> (
 }
 
 /// Implementation for the `availability_cores` function of the runtime API.
-pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::BlockNumber>> {
+pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::Hash, T::BlockNumber>> {
 	let cores = <scheduler::Module<T>>::availability_cores();
 	let parachains = <paras::Module<T>>::parachains();
 	let config = <configuration::Module<T>>::config();
@@ -96,7 +96,6 @@ pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::BlockNum
 
 					let backed_in_number = pending_availability.backed_in_number().clone();
 					OccupiedCore {
-						para_id,
 						next_up_on_available: <scheduler::Module<T>>::next_up_on_available(
 							CoreIndex(i as u32)
 						),
@@ -113,6 +112,8 @@ pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::BlockNum
 							backed_in_number,
 							pending_availability.core_occupied(),
 						),
+						candidate_hash: pending_availability.candidate_hash(),
+						candidate_descriptor: pending_availability.candidate_descriptor().clone(),
 					}
 				}
 				CoreOccupied::Parathread(p) => {
@@ -123,7 +124,6 @@ pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::BlockNum
 
 					let backed_in_number = pending_availability.backed_in_number().clone();
 					OccupiedCore {
-						para_id,
 						next_up_on_available: <scheduler::Module<T>>::next_up_on_available(
 							CoreIndex(i as u32)
 						),
@@ -140,6 +140,8 @@ pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::BlockNum
 							backed_in_number,
 							pending_availability.core_occupied(),
 						),
+						candidate_hash: pending_availability.candidate_hash(),
+						candidate_descriptor: pending_availability.candidate_descriptor().clone(),
 					}
 				}
 			})

polkadot/runtime/polkadot/src/lib.rs

@@ -1122,7 +1122,7 @@ sp_api::impl_runtime_apis! {
 			(Vec::new(), GroupRotationInfo { session_start_block: 0, group_rotation_frequency: 0, now: 0 })
 		}
 
-		fn availability_cores() -> Vec<CoreState<BlockNumber>> {
+		fn availability_cores() -> Vec<CoreState<Hash, BlockNumber>> {
 			Vec::new()
 		}
 

polkadot/runtime/rococo/src/lib.rs

@@ -691,7 +691,7 @@ sp_api::impl_runtime_apis! {
 			runtime_api_impl::validator_groups::<Runtime>()
 		}
 
-		fn availability_cores() -> Vec<CoreState<BlockNumber>> {
+		fn availability_cores() -> Vec<CoreState<Hash, BlockNumber>> {
 			runtime_api_impl::availability_cores::<Runtime>()
 		}
 

polkadot/runtime/test-runtime/src/lib.rs

@@ -631,7 +631,7 @@ sp_api::impl_runtime_apis! {
 			runtime_impl::validator_groups::<Runtime>()
 		}
 
-		fn availability_cores() -> Vec<CoreState<BlockNumber>> {
+		fn availability_cores() -> Vec<CoreState<Hash, BlockNumber>> {
 			runtime_impl::availability_cores::<Runtime>()
 		}
 

polkadot/runtime/westend/src/lib.rs

@@ -844,7 +844,7 @@ sp_api::impl_runtime_apis! {
 			(Vec::new(), GroupRotationInfo { session_start_block: 0, group_rotation_frequency: 0, now: 0 })
 		}
 
-		fn availability_cores() -> Vec<CoreState<BlockNumber>> {
+		fn availability_cores() -> Vec<CoreState<Hash, BlockNumber>> {
 			Vec::new()
 		}