Integrate Approval Voting into Overseer / Service / GRANDPA (#2412)

* integrate approval voting into overseer

* expose public API and make keystore arc

* integrate overseer in service

* guide: `ApprovedAncestor` returns block number

* return block number along with hash from ApprovedAncestor

* introduce a voting rule for reporting on approval checking

* integrate the delay voting rule

* Rococo configuration

* fix compilation and add slack

* fix web-wasm build

* tweak parameterization

* migrate voting rules to asycn

* remove hack comment

polkadot/Cargo.lock

@@ -5851,6 +5851,7 @@ dependencies = [
  "polkadot-collator-protocol",
  "polkadot-network-bridge",
  "polkadot-node-collation-generation",
+ "polkadot-node-core-approval-voting",
  "polkadot-node-core-av-store",
  "polkadot-node-core-backing",
  "polkadot-node-core-bitfield-signing",
@@ -5883,6 +5884,7 @@ dependencies = [
  "sc-executor",
  "sc-finality-grandpa",
  "sc-finality-grandpa-warp-sync",
+ "sc-keystore",
  "sc-network",
  "sc-service",
  "sc-telemetry",

polkadot/node/core/approval-voting/src/lib.rs

@@ -76,11 +76,23 @@ const LOG_TARGET: &str = "approval_voting";
 
 /// The approval voting subsystem.
 pub struct ApprovalVotingSubsystem<T> {
-	keystore: LocalKeystore,
+	keystore: Arc<LocalKeystore>,
 	slot_duration_millis: u64,
 	db: Arc<T>,
 }
 
+impl<T> ApprovalVotingSubsystem<T> {
+	/// Create a new approval voting subsystem with the given keystore, slot duration,
+	/// and underlying DB.
+	pub fn new(keystore: Arc<LocalKeystore>, slot_duration_millis: u64, db: Arc<T>) -> Self {
+		ApprovalVotingSubsystem {
+			keystore,
+			slot_duration_millis,
+			db,
+		}
+	}
+}
+
 impl<T, C> Subsystem<C> for ApprovalVotingSubsystem<T>
 	where T: AuxStore + Send + Sync + 'static, C: SubsystemContext<Message = ApprovalVotingMessage> {
 	fn start(self, ctx: C) -> SpawnedSubsystem {
@@ -229,7 +241,7 @@ use approval_db_v1_reader::ApprovalDBV1Reader;
 
 struct State<T> {
 	session_window: import::RollingSessionWindow,
-	keystore: LocalKeystore,
+	keystore: Arc<LocalKeystore>,
 	slot_duration_millis: u64,
 	db: T,
 	clock: Box<dyn Clock + Send + Sync>,
@@ -529,10 +541,10 @@ async fn handle_approved_ancestor(
 	db: &impl DBReader,
 	target: Hash,
 	lower_bound: BlockNumber,
-) -> SubsystemResult<Option<Hash>> {
+) -> SubsystemResult<Option<(Hash, BlockNumber)>> {
 	let mut all_approved_max = None;
 
-	let block_number = {
+	let target_number = {
 		let (tx, rx) = oneshot::channel();
 
 		ctx.send_message(ChainApiMessage::BlockNumber(target, tx).into()).await;
@@ -544,17 +556,17 @@ async fn handle_approved_ancestor(
 		}
 	};
 
-	if block_number <= lower_bound { return Ok(None) }
+	if target_number <= lower_bound { return Ok(None) }
 
 	// request ancestors up to but not including the lower bound,
 	// as a vote on the lower bound is implied if we cannot find
 	// anything else.
-	let ancestry = if block_number > lower_bound + 1 {
+	let ancestry = if target_number > lower_bound + 1 {
 		let (tx, rx) = oneshot::channel();
 
 		ctx.send_message(ChainApiMessage::Ancestors {
 			hash: target,
-			k: (block_number - (lower_bound + 1)) as usize,
+			k: (target_number - (lower_bound + 1)) as usize,
 			response_channel: tx,
 		}.into()).await;
 
@@ -566,7 +578,7 @@ async fn handle_approved_ancestor(
 		Vec::new()
 	};
 
-	for block_hash in std::iter::once(target).chain(ancestry) {
+	for (i, block_hash) in std::iter::once(target).chain(ancestry).enumerate() {
 		// Block entries should be present as the assumption is that
 		// nothing here is finalized. If we encounter any missing block
 		// entries we can fail.
@@ -577,7 +589,9 @@ async fn handle_approved_ancestor(
 
 		if entry.is_fully_approved() {
 			if all_approved_max.is_none() {
-				all_approved_max = Some(block_hash);
+				// First iteration of the loop is target, i = 0. After that,
+				// ancestry is moving backwards.
+				all_approved_max = Some((block_hash, target_number - i as BlockNumber));
 			}
 		} else {
 			all_approved_max = None;

polkadot/node/core/approval-voting/src/tests.rs

@@ -184,7 +184,7 @@ impl DBReader for TestStore {
 fn blank_state() -> State<TestStore> {
 	State {
 		session_window: import::RollingSessionWindow::default(),
-		keystore: LocalKeystore::in_memory(),
+		keystore: Arc::new(LocalKeystore::in_memory()),
 		slot_duration_millis: SLOT_DURATION_MILLIS,
 		db: TestStore::default(),
 		clock: Box::new(MockClock::default()),
@@ -1490,7 +1490,7 @@ fn approved_ancestor_all_approved() {
 	let test_fut = Box::pin(async move {
 		assert_eq!(
 			handle_approved_ancestor(&mut ctx, &state.db, block_hash_4, 0).await.unwrap(),
-			Some(block_hash_4),
+			Some((block_hash_4, 4)),
 		)
 	});
 
@@ -1572,7 +1572,7 @@ fn approved_ancestor_missing_approval() {
 	let test_fut = Box::pin(async move {
 		assert_eq!(
 			handle_approved_ancestor(&mut ctx, &state.db, block_hash_4, 0).await.unwrap(),
-			Some(block_hash_2),
+			Some((block_hash_2, 2)),
 		)
 	});
 

polkadot/node/overseer/src/lib.rs

@@ -86,6 +86,7 @@ use polkadot_subsystem::messages::{
 	ProvisionerMessage, PoVDistributionMessage, RuntimeApiMessage,
 	AvailabilityStoreMessage, NetworkBridgeMessage, AllMessages, CollationGenerationMessage,
 	CollatorProtocolMessage, AvailabilityRecoveryMessage, ApprovalDistributionMessage,
+	ApprovalVotingMessage,
 };
 pub use polkadot_subsystem::{
 	Subsystem, SubsystemContext, OverseerSignal, FromOverseer, SubsystemError, SubsystemResult,
@@ -561,6 +562,9 @@ pub struct Overseer<S> {
 	/// An Approval Distribution subsystem.
 	approval_distribution_subsystem: OverseenSubsystem<ApprovalDistributionMessage>,
 
+	/// An Approval Voting subsystem.
+	approval_voting_subsystem: OverseenSubsystem<ApprovalVotingMessage>,
+
 	/// Spawner to spawn tasks to.
 	s: S,
 
@@ -601,7 +605,7 @@ pub struct Overseer<S> {
 /// subsystems are implemented and the rest can be mocked with the [`DummySubsystem`].
 pub struct AllSubsystems<
 	CV = (), CB = (), CS = (), SD = (), AD = (), AR = (), BS = (), BD = (), P = (),
-	PoVD = (), RA = (), AS = (), NB = (), CA = (), CG = (), CP = (), ApD = (),
+	PoVD = (), RA = (), AS = (), NB = (), CA = (), CG = (), CP = (), ApD = (), ApV = (),
 > {
 	/// A candidate validation subsystem.
 	pub candidate_validation: CV,
@@ -637,10 +641,12 @@ pub struct AllSubsystems<
 	pub collator_protocol: CP,
 	/// An Approval Distribution subsystem.
 	pub approval_distribution: ApD,
+	/// An Approval Voting subsystem.
+	pub approval_voting: ApV,
 }
 
-impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
+impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV>
-	AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
+	AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV>
 {
 	/// Create a new instance of [`AllSubsystems`].
 	///
@@ -672,6 +678,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 		DummySubsystem,
 		DummySubsystem,
 		DummySubsystem,
+		DummySubsystem,
 	> {
 		AllSubsystems {
 			candidate_validation: DummySubsystem,
@@ -691,6 +698,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: DummySubsystem,
 			collator_protocol: DummySubsystem,
 			approval_distribution: DummySubsystem,
+			approval_voting: DummySubsystem,
 		}
 	}
 
@@ -698,7 +706,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_candidate_validation<NEW>(
 		self,
 		candidate_validation: NEW,
-	) -> AllSubsystems<NEW, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<NEW, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -717,6 +725,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -724,7 +733,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_candidate_backing<NEW>(
 		self,
 		candidate_backing: NEW,
-	) -> AllSubsystems<CV, NEW, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, NEW, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing,
@@ -743,6 +752,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -750,7 +760,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_candidate_selection<NEW>(
 		self,
 		candidate_selection: NEW,
-	) -> AllSubsystems<CV, CB, NEW, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, NEW, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -769,6 +779,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -776,7 +787,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_statement_distribution<NEW>(
 		self,
 		statement_distribution: NEW,
-	) -> AllSubsystems<CV, CB, CS, NEW, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, NEW, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -795,6 +806,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -802,7 +814,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_availability_distribution<NEW>(
 		self,
 		availability_distribution: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, NEW, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, NEW, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -821,6 +833,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -828,7 +841,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_availability_recovery<NEW>(
 		self,
 		availability_recovery: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, NEW, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, NEW, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -847,6 +860,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -854,7 +868,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_bitfield_signing<NEW>(
 		self,
 		bitfield_signing: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, NEW, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, NEW, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -873,6 +887,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -880,7 +895,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_bitfield_distribution<NEW>(
 		self,
 		bitfield_distribution: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, NEW, P, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, NEW, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -899,6 +914,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -906,7 +922,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_provisioner<NEW>(
 		self,
 		provisioner: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, NEW, PoVD, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, NEW, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -925,6 +941,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -932,7 +949,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_pov_distribution<NEW>(
 		self,
 		pov_distribution: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, NEW, RA, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, NEW, RA, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -951,6 +968,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -958,7 +976,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_runtime_api<NEW>(
 		self,
 		runtime_api: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, NEW, AS, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, NEW, AS, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -977,6 +995,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -984,7 +1003,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_availability_store<NEW>(
 		self,
 		availability_store: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, NEW, NB, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, NEW, NB, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -1003,6 +1022,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -1010,7 +1030,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_network_bridge<NEW>(
 		self,
 		network_bridge: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NEW, CA, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NEW, CA, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -1029,6 +1049,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -1036,7 +1057,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_chain_api<NEW>(
 		self,
 		chain_api: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, NEW, CG, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, NEW, CG, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -1055,6 +1076,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -1062,7 +1084,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_collation_generation<NEW>(
 		self,
 		collation_generation: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, NEW, CP, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, NEW, CP, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -1081,6 +1103,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -1088,7 +1111,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_collator_protocol<NEW>(
 		self,
 		collator_protocol: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, NEW, ApD> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, NEW, ApD, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -1107,6 +1130,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol,
 			approval_distribution: self.approval_distribution,
+			approval_voting: self.approval_voting,
 		}
 	}
 
@@ -1114,7 +1138,7 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 	pub fn replace_approval_distribution<NEW>(
 		self,
 		approval_distribution: NEW,
-	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, NEW> {
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, NEW, ApV> {
 		AllSubsystems {
 			candidate_validation: self.candidate_validation,
 			candidate_backing: self.candidate_backing,
@@ -1133,6 +1157,34 @@ impl<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>
 			collation_generation: self.collation_generation,
 			collator_protocol: self.collator_protocol,
 			approval_distribution,
+			approval_voting: self.approval_voting,
+		}
+	}
+
+	/// Replace the `approval_voting` instance in `self`.
+	pub fn replace_approval_voting<NEW>(
+		self,
+		approval_voting: NEW,
+	) -> AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, NEW> {
+		AllSubsystems {
+			candidate_validation: self.candidate_validation,
+			candidate_backing: self.candidate_backing,
+			candidate_selection: self.candidate_selection,
+			statement_distribution: self.statement_distribution,
+			availability_distribution: self.availability_distribution,
+			availability_recovery: self.availability_recovery,
+			bitfield_signing: self.bitfield_signing,
+			bitfield_distribution: self.bitfield_distribution,
+			provisioner: self.provisioner,
+			pov_distribution: self.pov_distribution,
+			runtime_api: self.runtime_api,
+			availability_store: self.availability_store,
+			network_bridge: self.network_bridge,
+			chain_api: self.chain_api,
+			collation_generation: self.collation_generation,
+			collator_protocol: self.collator_protocol,
+			approval_distribution: self.approval_distribution,
+			approval_voting
 		}
 	}
 }
@@ -1343,9 +1395,9 @@ where
 	/// #
 	/// # }); }
 	/// ```
-	pub fn new<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>(
+	pub fn new<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV>(
 		leaves: impl IntoIterator<Item = BlockInfo>,
-		all_subsystems: AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD>,
+		all_subsystems: AllSubsystems<CV, CB, CS, SD, AD, AR, BS, BD, P, PoVD, RA, AS, NB, CA, CG, CP, ApD, ApV>,
 		prometheus_registry: Option<&prometheus::Registry>,
 		mut s: S,
 	) -> SubsystemResult<(Self, OverseerHandler)>
@@ -1367,6 +1419,7 @@ where
 		CG: Subsystem<OverseerSubsystemContext<CollationGenerationMessage>> + Send,
 		CP: Subsystem<OverseerSubsystemContext<CollatorProtocolMessage>> + Send,
 		ApD: Subsystem<OverseerSubsystemContext<ApprovalDistributionMessage>> + Send,
+		ApV: Subsystem<OverseerSubsystemContext<ApprovalVotingMessage>> + Send,
 	{
 		let (events_tx, events_rx) = metered::channel(CHANNEL_CAPACITY, "overseer_events");
 
@@ -1551,6 +1604,15 @@ where
 			&mut seed,
 		)?;
 
+		let approval_voting_subsystem = spawn(
+			&mut s,
+			&mut running_subsystems,
+			metered::UnboundedMeteredSender::<_>::clone(&to_overseer_tx),
+			all_subsystems.approval_voting,
+			&metrics,
+			&mut seed,
+		)?;
+
 		let leaves = leaves
 			.into_iter()
 			.map(|BlockInfo { hash, parent_hash: _, number }| (hash, number))
@@ -1577,6 +1639,7 @@ where
 			collation_generation_subsystem,
 			collator_protocol_subsystem,
 			approval_distribution_subsystem,
+			approval_voting_subsystem,
 			s,
 			running_subsystems,
 			to_overseer_rx: to_overseer_rx.fuse(),
@@ -1610,6 +1673,7 @@ where
 		let _ = self.collator_protocol_subsystem.send_signal(OverseerSignal::Conclude).await;
 		let _ = self.collation_generation_subsystem.send_signal(OverseerSignal::Conclude).await;
 		let _ = self.approval_distribution_subsystem.send_signal(OverseerSignal::Conclude).await;
+		let _ = self.approval_voting_subsystem.send_signal(OverseerSignal::Conclude).await;
 
 		let mut stop_delay = Delay::new(Duration::from_secs(STOP_DELAY)).fuse();
 
@@ -1778,7 +1842,8 @@ where
 		self.chain_api_subsystem.send_signal(signal.clone()).await?;
 		self.collator_protocol_subsystem.send_signal(signal.clone()).await?;
 		self.collation_generation_subsystem.send_signal(signal.clone()).await?;
-		self.approval_distribution_subsystem.send_signal(signal).await?;
+		self.approval_distribution_subsystem.send_signal(signal.clone()).await?;
+		self.approval_voting_subsystem.send_signal(signal).await?;
 
 		Ok(())
 	}
@@ -1804,7 +1869,7 @@ where
 				self.availability_distribution_subsystem.send_message(msg).await?;
 			},
 			AllMessages::AvailabilityRecovery(msg) => {
-				let _ = self.availability_recovery_subsystem.send_message(msg).await;
+				self.availability_recovery_subsystem.send_message(msg).await?;
 			},
 			AllMessages::BitfieldDistribution(msg) => {
 				self.bitfield_distribution_subsystem.send_message(msg).await?;
@@ -1837,10 +1902,10 @@ where
 				self.collator_protocol_subsystem.send_message(msg).await?;
 			},
 			AllMessages::ApprovalDistribution(msg) => {
-				let _ = self.approval_distribution_subsystem.send_message(msg).await;
+				self.approval_distribution_subsystem.send_message(msg).await?;
 			},
-			AllMessages::ApprovalVoting(_msg) => {
+			AllMessages::ApprovalVoting(msg) => {
-				// FIXME: https://github.com/paritytech/polkadot/issues/2321
+				self.approval_voting_subsystem.send_message(msg).await?;
 			},
 		}
 
@@ -2696,6 +2761,11 @@ mod tests {
 		ApprovalDistributionMessage::NewBlocks(Default::default())
 	}
 
+	fn test_approval_voting_msg() -> ApprovalVotingMessage {
+		let (sender, _) = oneshot::channel();
+		ApprovalVotingMessage::ApprovedAncestor(Default::default(), 0, sender)
+	}
+
 	// Checks that `stop`, `broadcast_signal` and `broadcast_message` are implemented correctly.
 	#[test]
 	fn overseer_all_subsystems_receive_signals_and_messages() {
@@ -2730,6 +2800,7 @@ mod tests {
 				network_bridge: subsystem.clone(),
 				chain_api: subsystem.clone(),
 				approval_distribution: subsystem.clone(),
+				approval_voting: subsystem.clone(),
 			};
 			let (overseer, mut handler) = Overseer::new(
 				vec![],
@@ -2767,13 +2838,14 @@ mod tests {
 			handler.send_msg(AllMessages::NetworkBridge(test_network_bridge_msg())).await;
 			handler.send_msg(AllMessages::ChainApi(test_chain_api_msg())).await;
 			handler.send_msg(AllMessages::ApprovalDistribution(test_approval_distribution_msg())).await;
+			handler.send_msg(AllMessages::ApprovalVoting(test_approval_voting_msg())).await;
 
 			// send a stop signal to each subsystems
 			handler.stop().await;
 
 			select! {
 				res = overseer_fut => {
-					const NUM_SUBSYSTEMS: usize = 17;
+					const NUM_SUBSYSTEMS: usize = 18;
 
 					assert_eq!(stop_signals_received.load(atomic::Ordering::SeqCst), NUM_SUBSYSTEMS);
 					// x2 because of broadcast_signal on startup

polkadot/node/service/Cargo.toml

@@ -19,6 +19,7 @@ sc-executor = { git = "https://github.com/paritytech/substrate", branch = "maste
 sc-finality-grandpa-warp-sync = { git = "https://github.com/paritytech/substrate", branch = "master", optional = true }
 sc-network = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-transaction-pool = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sc-keystore = { git = "https://github.com/paritytech/substrate", branch = "master" }
 service = { package = "sc-service", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 telemetry = { package = "sc-telemetry", git = "https://github.com/paritytech/substrate", branch = "master" }
 
@@ -95,6 +96,7 @@ polkadot-node-core-runtime-api = { path = "../core/runtime-api", optional = true
 polkadot-pov-distribution = { path = "../network/pov-distribution", optional = true }
 polkadot-statement-distribution = { path = "../network/statement-distribution", optional = true }
 polkadot-approval-distribution = { path = "../network/approval-distribution", optional = true }
+polkadot-node-core-approval-voting = { path = "../core/approval-voting", optional = true }
 
 [dev-dependencies]
 polkadot-test-client = { path = "../test/client" }
@@ -132,4 +134,5 @@ real-overseer = [
 	"polkadot-pov-distribution",
 	"polkadot-statement-distribution",
 	"polkadot-approval-distribution",
+	"polkadot-node-core-approval-voting",
 ]

polkadot/node/service/src/chain_spec.rs

@@ -870,7 +870,6 @@ fn rococo_staging_testnet_config_genesis(wasm_binary: &[u8]) -> rococo_runtime::
 				group_rotation_frequency: 20,
 				chain_availability_period: 4,
 				thread_availability_period: 4,
-				no_show_slots: 10,
 				max_upward_queue_count: 8,
 				max_upward_queue_size: 8 * 1024,
 				max_downward_message_size: 1024,
@@ -893,6 +892,11 @@ fn rococo_staging_testnet_config_genesis(wasm_binary: &[u8]) -> rococo_runtime::
 				hrmp_max_parachain_outbound_channels: 4,
 				hrmp_max_parathread_outbound_channels: 4,
 				hrmp_max_message_num_per_candidate: 5,
+				no_show_slots: 2,
+				n_delay_tranches: 25,
+				needed_approvals: 2,
+				relay_vrf_modulo_samples: 10,
+				zeroth_delay_tranche_width: 0,
 				..Default::default()
 			},
 		}),
@@ -1376,7 +1380,6 @@ pub fn rococo_testnet_genesis(
 				group_rotation_frequency: 20,
 				chain_availability_period: 4,
 				thread_availability_period: 4,
-				no_show_slots: 10,
 				max_upward_queue_count: 8,
 				max_upward_queue_size: 8 * 1024,
 				max_downward_message_size: 1024,
@@ -1399,6 +1402,11 @@ pub fn rococo_testnet_genesis(
 				hrmp_max_parachain_outbound_channels: 4,
 				hrmp_max_parathread_outbound_channels: 4,
 				hrmp_max_message_num_per_candidate: 5,
+				no_show_slots: 2,
+				n_delay_tranches: 25,
+				needed_approvals: 2,
+				relay_vrf_modulo_samples: 10,
+				zeroth_delay_tranche_width: 0,
 				..Default::default()
 			},
 		}),

polkadot/node/service/src/grandpa_support.rs

@@ -18,9 +18,138 @@
 
 use std::sync::Arc;
 
-#[cfg(feature = "full-node")]
+use polkadot_primitives::v1::{Block as PolkadotBlock, Header as PolkadotHeader, BlockNumber, Hash};
-use polkadot_primitives::v1::Hash;
+use polkadot_subsystem::messages::ApprovalVotingMessage;
+
 use sp_runtime::traits::{Block as BlockT, NumberFor};
+use sp_runtime::generic::BlockId;
+use sp_runtime::traits::Header as _;
+
+use prometheus_endpoint::{self, Registry};
+use polkadot_overseer::OverseerHandler;
+
+use futures::channel::oneshot;
+
+/// A custom GRANDPA voting rule that acts as a diagnostic for the approval
+/// voting subsystem's desired votes.
+///
+/// The practical effect of this voting rule is to implement a fixed delay of
+/// blocks and to issue a prometheus metric on the lag behind the head that
+/// approval checking would indicate.
+#[cfg(feature = "full-node")]
+#[derive(Clone)]
+pub(crate) struct ApprovalCheckingDiagnostic {
+	checking_lag: Option<prometheus_endpoint::Histogram>,
+	overseer: OverseerHandler,
+}
+
+#[cfg(feature = "full-node")]
+impl ApprovalCheckingDiagnostic {
+	/// Create a new approval checking diagnostic voting rule.
+	pub fn new(overseer: OverseerHandler, registry: Option<&Registry>)
+		-> Result<Self, prometheus_endpoint::PrometheusError>
+	{
+		Ok(ApprovalCheckingDiagnostic {
+			checking_lag: if let Some(registry) = registry {
+				Some(prometheus_endpoint::register(
+					prometheus_endpoint::Histogram::with_opts(
+						prometheus_endpoint::HistogramOpts::new(
+							"approval_checking_finality_lag",
+							"How far behind the head of the chain the Approval Checking protocol wants to vote",
+						).buckets(vec![1.0, 2.0, 3.0, 4.0, 5.0, 10.0, 20.0, 30.0, 40.0, 50.0])
+					)?,
+					registry,
+				)?)
+			} else {
+				None
+			},
+			overseer,
+		})
+	}
+}
+
+#[cfg(feature = "full-node")]
+impl<B> grandpa::VotingRule<PolkadotBlock, B> for ApprovalCheckingDiagnostic
+	where B: sp_blockchain::HeaderBackend<PolkadotBlock>
+{
+	fn restrict_vote(
+		&self,
+		backend: Arc<B>,
+		base: &PolkadotHeader,
+		_best_target: &PolkadotHeader,
+		current_target: &PolkadotHeader,
+	) -> grandpa::VotingRuleResult<PolkadotBlock> {
+		// always wait 50 blocks behind the head to finalize.
+		const DIAGNOSTIC_GRANDPA_DELAY: BlockNumber = 50;
+
+		let aux = || {
+			let find_target = |target_number: BlockNumber, current_header: &PolkadotHeader| {
+				let mut target_hash = current_header.hash();
+				let mut target_header = current_header.clone();
+
+				loop {
+					if *target_header.number() < target_number {
+						unreachable!(
+							"we are traversing backwards from a known block; \
+							blocks are stored contiguously; \
+							qed"
+						);
+					}
+
+					if *target_header.number() == target_number {
+						return Some((target_hash, target_number));
+					}
+
+					target_hash = *target_header.parent_hash();
+					target_header = backend.header(BlockId::Hash(target_hash)).ok()?
+						.expect("Header known to exist due to the existence of one of its descendents; qed");
+				}
+			};
+
+			let target_number = std::cmp::max(
+				current_target.number().saturating_sub(DIAGNOSTIC_GRANDPA_DELAY),
+				base.number().clone(),
+			);
+
+			find_target(target_number, current_target)
+		};
+
+		let actual_vote_target = aux();
+
+		// Query approval checking and issue metrics.
+		let mut overseer = self.overseer.clone();
+		let checking_lag = self.checking_lag.clone();
+
+		let current_hash = current_target.hash();
+		let current_number = current_target.number.clone();
+
+		let base_number = base.number;
+
+		Box::pin(async move {
+			let (tx, rx) = oneshot::channel();
+			let approval_checking_subsystem_vote = {
+				overseer.send_msg(ApprovalVotingMessage::ApprovedAncestor(
+					current_hash,
+					base_number,
+					tx,
+				)).await;
+
+				rx.await.ok().and_then(|v| v)
+			};
+
+			let approval_checking_subsystem_lag = approval_checking_subsystem_vote.map_or(
+				current_number - base_number,
+				|(_h, n)| current_number - n,
+			);
+
+			if let Some(ref checking_lag) = checking_lag {
+				checking_lag.observe(approval_checking_subsystem_lag as _);
+			}
+
+			actual_vote_target
+		})
+	}
+}
 
 /// A custom GRANDPA voting rule that "pauses" voting (i.e. keeps voting for the
 /// same last finalized block) after a given block at height `N` has been
@@ -42,9 +171,6 @@ where
 		current_target: &Block::Header,
 	) -> grandpa::VotingRuleResult<Block> {
 		let aux = || {
-			use sp_runtime::generic::BlockId;
-			use sp_runtime::traits::Header as _;
-
 			// walk backwards until we find the target block
 			let find_target = |target_number: NumberFor<Block>, current_header: &Block::Header| {
 				let mut target_hash = current_header.hash();

polkadot/node/service/src/lib.rs

@@ -22,7 +22,6 @@ pub mod chain_spec;
 mod grandpa_support;
 mod client;
 
-use grandpa::{self, FinalityProofProvider as GrandpaFinalityProofProvider};
 #[cfg(feature = "full-node")]
 use {
 	std::convert::TryInto,
@@ -35,10 +34,11 @@ use {
 	polkadot_primitives::v1::ParachainHost,
 	sc_authority_discovery::Service as AuthorityDiscoveryService,
 	sp_blockchain::HeaderBackend,
-	sp_keystore::SyncCryptoStorePtr,
 	sp_trie::PrefixedMemoryDB,
-	sc_client_api::ExecutorProvider,
+	sc_client_api::{AuxStore, ExecutorProvider},
+	sc_keystore::LocalKeystore,
 	babe_primitives::BabeApi,
+	grandpa::{self, FinalityProofProvider as GrandpaFinalityProofProvider},
 };
 #[cfg(feature = "real-overseer")]
 use polkadot_network_bridge::RequestMultiplexer;
@@ -348,7 +348,7 @@ fn new_partial<RuntimeApi, Executor>(config: &mut Configuration, jaeger_agent: O
 #[cfg(all(feature="full-node", not(feature = "real-overseer")))]
 fn real_overseer<Spawner, RuntimeClient>(
 	leaves: impl IntoIterator<Item = BlockInfo>,
-	_: SyncCryptoStorePtr,
+	_: Arc<LocalKeystore>,
 	_: Arc<RuntimeClient>,
 	_: AvailabilityConfig,
 	_: Arc<sc_network::NetworkService<Block, Hash>>,
@@ -361,8 +361,8 @@ fn real_overseer<Spawner, RuntimeClient>(
 	_: u64,
 ) -> Result<(Overseer<Spawner>, OverseerHandler), Error>
 where
-	RuntimeClient: 'static + ProvideRuntimeApi<Block> + HeaderBackend<Block>,
+	RuntimeClient: 'static + ProvideRuntimeApi<Block> + HeaderBackend<Block> + AuxStore,
-	RuntimeClient::Api: ParachainHost<Block>,
+	RuntimeClient::Api: ParachainHost<Block> + BabeApi<Block>,
 	Spawner: 'static + SpawnNamed + Clone + Unpin,
 {
 	Overseer::new(
@@ -376,7 +376,7 @@ where
 #[cfg(all(feature = "full-node", feature = "real-overseer"))]
 fn real_overseer<Spawner, RuntimeClient>(
 	leaves: impl IntoIterator<Item = BlockInfo>,
-	keystore: SyncCryptoStorePtr,
+	keystore: Arc<LocalKeystore>,
 	runtime_client: Arc<RuntimeClient>,
 	availability_config: AvailabilityConfig,
 	network_service: Arc<sc_network::NetworkService<Block, Hash>>,
@@ -386,10 +386,10 @@ fn real_overseer<Spawner, RuntimeClient>(
 	spawner: Spawner,
 	is_collator: IsCollator,
 	isolation_strategy: IsolationStrategy,
-	_slot_duration: u64, // TODO [now]: instantiate approval voting.
+	slot_duration: u64,
 ) -> Result<(Overseer<Spawner>, OverseerHandler), Error>
 where
-	RuntimeClient: 'static + ProvideRuntimeApi<Block> + HeaderBackend<Block>,
+	RuntimeClient: 'static + ProvideRuntimeApi<Block> + HeaderBackend<Block> + AuxStore,
 	RuntimeClient::Api: ParachainHost<Block> + BabeApi<Block>,
 	Spawner: 'static + SpawnNamed + Clone + Unpin,
 {
@@ -412,6 +412,7 @@ where
 	use polkadot_statement_distribution::StatementDistribution as StatementDistributionSubsystem;
 	use polkadot_availability_recovery::AvailabilityRecoverySubsystem;
 	use polkadot_approval_distribution::ApprovalDistribution as ApprovalDistributionSubsystem;
+	use polkadot_node_core_approval_voting::ApprovalVotingSubsystem;
 
 	let all_subsystems = AllSubsystems {
 		availability_distribution: AvailabilityDistributionSubsystem::new(
@@ -477,7 +478,7 @@ where
 			Metrics::register(registry)?,
 		),
 		runtime_api: RuntimeApiSubsystem::new(
-			runtime_client,
+			runtime_client.clone(),
 			Metrics::register(registry)?,
 			spawner.clone(),
 		),
@@ -487,6 +488,11 @@ where
 		approval_distribution: ApprovalDistributionSubsystem::new(
 			Metrics::register(registry)?,
 		),
+		approval_voting: ApprovalVotingSubsystem::new(
+			keystore.clone(),
+			slot_duration,
+			runtime_client.clone(),
+		),
 	};
 
 	Overseer::new(
@@ -563,7 +569,12 @@ pub fn new_full<RuntimeApi, Executor>(
 	let role = config.role.clone();
 	let force_authoring = config.force_authoring;
 	let backoff_authoring_blocks =
-		Some(sc_consensus_slots::BackoffAuthoringOnFinalizedHeadLagging::default());
+		Some(sc_consensus_slots::BackoffAuthoringOnFinalizedHeadLagging {
+			#[cfg(feature = "real-overseer")]
+			unfinalized_slack: 100,
+			..Default::default()
+		});
+
 	let disable_grandpa = config.disable_grandpa;
 	let name = config.network.node_name.clone();
 
@@ -705,10 +716,18 @@ pub fn new_full<RuntimeApi, Executor>(
 
 	// we'd say let overseer_handler = authority_discovery_service.map(|authority_discovery_service|, ...),
 	// but in that case we couldn't use ? to propagate errors
-	let overseer_handler = if let Some(authority_discovery_service) = authority_discovery_service {
+	let local_keystore = keystore_container.local_keystore();
+	if local_keystore.is_none() {
+		tracing::info!("Cannot run as validator without local keystore.");
+	}
+
+	let maybe_params = local_keystore
+		.and_then(move |k| authority_discovery_service.map(|a| (a, k)));
+
+	let overseer_handler = if let Some((authority_discovery_service, keystore)) = maybe_params {
 		let (overseer, overseer_handler) = real_overseer(
 			leaves,
-			keystore_container.sync_keystore(),
+			keystore,
 			overseer_client.clone(),
 			availability_config,
 			network.clone(),
@@ -803,6 +822,17 @@ pub fn new_full<RuntimeApi, Executor>(
 		// add a custom voting rule to temporarily stop voting for new blocks
 		// after the given pause block is finalized and restarting after the
 		// given delay.
+		let builder = grandpa::VotingRulesBuilder::default();
+
+		let builder = if let Some(ref overseer) = overseer_handler {
+			builder.add(grandpa_support::ApprovalCheckingDiagnostic::new(
+				overseer.clone(),
+				prometheus_registry.as_ref(),
+			)?)
+		} else {
+			builder
+		};
+
 		let voting_rule = match grandpa_pause {
 			Some((block, delay)) => {
 				info!(
@@ -813,11 +843,11 @@ pub fn new_full<RuntimeApi, Executor>(
 					delay,
 				);
 
-				grandpa::VotingRulesBuilder::default()
+				builder
 					.add(grandpa_support::PauseAfterBlockFor(block, delay))
 					.build()
 			}
-			None => grandpa::VotingRulesBuilder::default().build(),
+			None => builder.build(),
 		};
 
 		let grandpa_config = grandpa::GrandpaParams {

polkadot/node/subsystem/src/messages.rs

@@ -661,7 +661,7 @@ pub enum ApprovalVotingMessage {
 	///
 	/// It can also return the same block hash, if that is acceptable to vote upon.
 	/// Return `None` if the input hash is unrecognized.
-	ApprovedAncestor(Hash, BlockNumber, oneshot::Sender<Option<Hash>>),
+	ApprovedAncestor(Hash, BlockNumber, oneshot::Sender<Option<(Hash, BlockNumber)>>),
 }
 
 /// Message to the Approval Distribution subsystem.

polkadot/roadmap/implementers-guide/src/node/approval/approval-voting.md

@@ -218,9 +218,9 @@ On receiving a `CheckAndImportApproval(indirect_approval_vote, response_channel)
 
 On receiving an `ApprovedAncestor(Hash, BlockNumber, response_channel)`:
   * Iterate over the ancestry of the hash all the way back to block number given, starting from the provided block hash.
-  * Keep track of an `all_approved_max: Option<Hash>`.
+  * Keep track of an `all_approved_max: Option<(Hash, BlockNumber)>`.
   * For each block hash encountered, load the `BlockEntry` associated. If any are not found, return `None` on the response channel and conclude.
-  * If the block entry's `approval_bitfield` has all bits set to 1 and `all_approved_max == None`, set `all_approved_max = Some(current_hash)`.
+  * If the block entry's `approval_bitfield` has all bits set to 1 and `all_approved_max == None`, set `all_approved_max = Some((current_hash, current_number))`.
   * If the block entry's `approval_bitfield` has any 0 bits, set `all_approved_max = None`.
   * After iterating all ancestry, return `all_approved_max`.
 

polkadot/roadmap/implementers-guide/src/types/overseer-protocol.md

@@ -81,7 +81,7 @@ enum ApprovalVotingMessage {
     ///
     /// It can also return the same block hash, if that is acceptable to vote upon.
     /// Return `None` if the input hash is unrecognized.
-    ApprovedAncestor(Hash, BlockNumber, ResponseChannel<Option<Hash>>),
+    ApprovedAncestor(Hash, BlockNumber, ResponseChannel<Option<(Hash, BlockNumber)>>),
 }
 ```