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/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)),
 		)
 	});