Persist block announcements (#3826)

* Persist block announcements

* Renamed sync requests to fork targets

* Fixed pruning detection condition

substrate/core/network/src/protocol/sync.rs

@@ -69,9 +69,6 @@ const MAJOR_SYNC_BLOCKS: u8 = 5;
 /// Number of recently announced blocks to track for each peer.
 const ANNOUNCE_HISTORY_SIZE: usize = 64;
 
-/// Max number of blocks to download for unknown forks.
-const MAX_UNKNOWN_FORK_DOWNLOAD_LEN: u32 = 32;
-
 /// Reputation change when a peer sent us a status message that led to a
 /// database read error.
 const BLOCKCHAIN_STATUS_READ_ERROR_REPUTATION_CHANGE: i32 = -(1 << 16);
@@ -125,8 +122,8 @@ pub struct ChainSync<B: BlockT> {
 	best_importing_number: NumberFor<B>,
 	/// Finality proof handler.
 	request_builder: Option<BoxFinalityProofRequestBuilder<B>>,
-	/// Explicit sync requests.
-	sync_requests: HashMap<B::Hash, SyncRequest<B>>,
+	/// Fork sync targets.
+	fork_targets: HashMap<B::Hash, ForkTarget<B>>,
 	/// A flag that caches idle state with no pending requests.
 	is_idle: bool,
 	/// A type to check incoming block announcements.
@@ -160,8 +157,9 @@ pub struct PeerInfo<B: BlockT> {
 	pub best_number: NumberFor<B>
 }
 
-struct SyncRequest<B: BlockT> {
+struct ForkTarget<B: BlockT> {
 	number: NumberFor<B>,
+	parent_hash: Option<B::Hash>,
 	peers: HashSet<PeerId>,
 }
 
@@ -242,13 +240,11 @@ pub enum OnBlockData<B: BlockT> {
 
 /// Result of [`ChainSync::on_block_announce`].
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub enum OnBlockAnnounce<B: BlockT> {
+pub enum OnBlockAnnounce {
 	/// The announcement does not require further handling.
 	Nothing,
 	/// The announcement header should be imported.
 	ImportHeader,
-	/// Another block request to the given peer is necessary.
-	Request(PeerId, BlockRequest<B>)
 }
 
 /// Result of [`ChainSync::on_block_justification`].
@@ -307,7 +303,7 @@ impl<B: BlockT> ChainSync<B> {
 			queue_blocks: Default::default(),
 			best_importing_number: Zero::zero(),
 			request_builder,
-			sync_requests: Default::default(),
+			fork_targets: Default::default(),
 			is_idle: false,
 			block_announce_validator,
 		}
@@ -462,7 +458,7 @@ impl<B: BlockT> ChainSync<B> {
 	// The implementation is similar to on_block_announce with unknown parent hash.
 	pub fn set_sync_fork_request(&mut self, peers: Vec<PeerId>, hash: &B::Hash, number: NumberFor<B>) {
 		if peers.is_empty() {
-			if let Some(_) = self.sync_requests.remove(hash) {
+			if let Some(_) = self.fork_targets.remove(hash) {
 				debug!(target: "sync", "Cleared sync request for block {:?} with {:?}", hash, peers);
 			}
 			return;
@@ -494,11 +490,12 @@ impl<B: BlockT> ChainSync<B> {
 			}
 		}
 
-		self.sync_requests
+		self.fork_targets
 			.entry(hash.clone())
-			.or_insert_with(|| SyncRequest {
+			.or_insert_with(|| ForkTarget {
 				number,
 				peers: Default::default(),
+				parent_hash: None,
 			})
 			.peers.extend(peers);
 	}
@@ -562,17 +559,30 @@ impl<B: BlockT> ChainSync<B> {
 		}
 		let blocks = &mut self.blocks;
 		let attrs = &self.required_block_attributes;
-		let sync_requests = &self.sync_requests;
+		let fork_targets = &self.fork_targets;
 		let mut have_requests = false;
 		let last_finalized = self.client.info().chain.finalized_number;
 		let best_queued = self.best_queued_number;
+		let client = &self.client;
+		let queue = &self.queue_blocks;
 		let iter = self.peers.iter_mut().filter_map(move |(id, peer)| {
 			if !peer.state.is_available() {
 				trace!(target: "sync", "Peer {} is busy", id);
 				return None
 			}
-			if let Some((hash, req)) = explicit_sync_request(id, sync_requests, best_queued, last_finalized, attrs) {
-				trace!(target: "sync", "Downloading explicitly requested block {:?} from {}", hash, id);
+			if let Some((hash, req)) = fork_sync_request(
+				id,
+				fork_targets,
+				best_queued,
+				last_finalized,
+				attrs,
+				|hash| if queue.contains(hash) {
+					BlockStatus::Queued
+				} else {
+					client.block_status(&BlockId::Hash(*hash)).unwrap_or(BlockStatus::Unknown)
+				},
+			) {
+				trace!(target: "sync", "Downloading fork {:?} from {}", hash, id);
 				peer.state = PeerSyncState::DownloadingStale(hash);
 				have_requests = true;
 				Some((id.clone(), req))
@@ -665,6 +675,26 @@ impl<B: BlockT> ChainSync<B> {
 							peer.state = PeerSyncState::AncestorSearch(next_num, next_state);
 							return Ok(OnBlockData::Request(who, ancestry_request::<B>(next_num)))
 						} else {
+							// Ancestry search is complete. Check if peer is on a stale fork unknown to us and
+							// add it to sync targets if necessary.
+							trace!(target: "sync", "Ancestry search complete. Ours={} ({}), Theirs={} ({}), Common={}",
+								self.best_queued_hash,
+								self.best_queued_number,
+								peer.best_hash,
+								peer.best_number,
+								peer.common_number
+							);
+							if peer.common_number < peer.best_number && peer.best_number < self.best_queued_number {
+								trace!(target: "sync", "Added fork target {} for {}" , peer.best_hash, who);
+								self.fork_targets
+									.entry(peer.best_hash.clone())
+									.or_insert_with(|| ForkTarget {
+										number: peer.best_number,
+										parent_hash: None,
+										peers: Default::default(),
+									})
+								.peers.insert(who);
+							}
 							peer.state = PeerSyncState::Available;
 							Vec::new()
 						}
@@ -922,14 +952,14 @@ impl<B: BlockT> ChainSync<B> {
 			self.best_queued_number = number;
 			self.best_queued_hash = *hash;
 		}
-		if let Some(_) = self.sync_requests.remove(&hash) {
-			trace!(target: "sync", "Completed explicit sync request {:?}", hash);
+		if let Some(_) = self.fork_targets.remove(&hash) {
+			trace!(target: "sync", "Completed fork sync {:?}", hash);
 		}
 		// Update common blocks
 		for (n, peer) in self.peers.iter_mut() {
 			if let PeerSyncState::AncestorSearch(_, _) = peer.state {
-				// Abort search.
-				peer.state = PeerSyncState::Available;
+				// Wait for ancestry search to complete first.
+				continue;
 			}
 			let new_common_number = if peer.best_number >= number {
 				number
@@ -952,12 +982,12 @@ impl<B: BlockT> ChainSync<B> {
 
 	/// Call when a node announces a new block.
 	///
-	/// If true is returned, then the caller MUST try to import passed
+	/// If `OnBlockAnnounce::ImportHeader` is returned, then the caller MUST try to import passed
 	/// header (call `on_block_data`). The network request isn't sent
 	/// in this case. Both hash and header is passed as an optimization
 	/// to avoid rehashing the header.
 	pub fn on_block_announce(&mut self, who: PeerId, hash: B::Hash, announce: &BlockAnnounce<B::Header>, is_best: bool)
-		-> OnBlockAnnounce<B>
+		-> OnBlockAnnounce
 	{
 		let header = &announce.header;
 		let number = *header.number();
@@ -1001,6 +1031,9 @@ impl<B: BlockT> ChainSync<B> {
 		// known block case
 		if known || self.is_already_downloading(&hash) {
 			trace!(target: "sync", "Known block announce from {}: {}", who, hash);
+			if let Some(target) = self.fork_targets.get_mut(&hash) {
+				target.peers.insert(who);
+			}
 			return OnBlockAnnounce::Nothing
 		}
 
@@ -1009,79 +1042,42 @@ impl<B: BlockT> ChainSync<B> {
 		match self.block_announce_validator.validate(&header, assoc_data) {
 			Ok(Validation::Success) => (),
 			Ok(Validation::Failure) => {
-				debug!(target: "sync", "block announcement validation of block {} from {} failed", hash, who);
+				debug!(target: "sync", "Block announcement validation of block {} from {} failed", hash, who);
 				return OnBlockAnnounce::Nothing
 			}
 			Err(e) => {
-				error!(target: "sync", "block announcement validation errored: {}", e);
+				error!(target: "sync", "Block announcement validation errored: {}", e);
 				return OnBlockAnnounce::Nothing
 			}
 		}
 
-		// stale block case
-		let requires_additional_data = !self.role.is_light();
-		if number <= self.best_queued_number {
-			if !(known_parent || self.is_already_downloading(header.parent_hash())) {
-				let block_status = self.client.block_status(&BlockId::Number(*header.number()))
-					.unwrap_or(BlockStatus::Unknown);
-				if block_status == BlockStatus::InChainPruned {
-					trace!(
-						target: "sync",
-						"Ignored unknown ancient block announced from {}: {} {:?}", who, hash, header
-					);
-					return OnBlockAnnounce::Nothing
-				}
-				trace!(
-					target: "sync",
-					"Considering new unknown stale block announced from {}: {} {:?}", who, hash, header
-				);
-				if let Some(request) = self.download_unknown_stale(&who, &hash) {
-					if requires_additional_data {
-						return OnBlockAnnounce::Request(who, request)
-					} else {
-						return OnBlockAnnounce::ImportHeader
-					}
-				} else {
-					return OnBlockAnnounce::Nothing
-				}
-			} else {
-				if ancient_parent {
-					trace!(target: "sync", "Ignored ancient stale block announced from {}: {} {:?}", who, hash, header);
-					return OnBlockAnnounce::Nothing
-				}
-				if let Some(request) = self.download_stale(&who, &hash) {
-					if requires_additional_data {
-						return OnBlockAnnounce::Request(who, request)
-					} else {
-						return OnBlockAnnounce::ImportHeader
-					}
-				} else {
-					return OnBlockAnnounce::Nothing
-				}
-			}
-		}
-
 		if ancient_parent {
 			trace!(target: "sync", "Ignored ancient block announced from {}: {} {:?}", who, hash, header);
 			return OnBlockAnnounce::Nothing
 		}
 
-		trace!(target: "sync", "Considering new block announced from {}: {} {:?}", who, hash, header);
-
-		let (range, request) = match self.select_new_blocks(who.clone()) {
-			Some((range, request)) => (range, request),
-			None => return OnBlockAnnounce::Nothing
-		};
-
-		let is_required_data_available = !requires_additional_data
-			&& range.end - range.start == One::one()
-			&& range.start == *header.number();
-
-		if !is_required_data_available {
-			return OnBlockAnnounce::Request(who, request)
+		let requires_additional_data = !self.role.is_light() || !known_parent;
+		if !requires_additional_data {
+			trace!(target: "sync", "Importing new header announced from {}: {} {:?}", who, hash, header);
+			return OnBlockAnnounce::ImportHeader
 		}
 
-		OnBlockAnnounce::ImportHeader
+		if number <= self.best_queued_number {
+			trace!(
+				target: "sync",
+				"Added sync target for block announced from {}: {} {:?}", who, hash, header
+			);
+			self.fork_targets
+				.entry(hash.clone())
+				.or_insert_with(|| ForkTarget {
+					number,
+					parent_hash: Some(header.parent_hash().clone()),
+					peers: Default::default(),
+				})
+			.peers.insert(who);
+		}
+
+		OnBlockAnnounce::Nothing
 	}
 
 	/// Call when a peer has disconnected.
@@ -1117,40 +1113,6 @@ impl<B: BlockT> ChainSync<B> {
 		})
 	}
 
-	/// Download old block with known parent.
-	fn download_stale(&mut self, who: &PeerId, hash: &B::Hash) -> Option<BlockRequest<B>> {
-		let peer = self.peers.get_mut(who)?;
-		if !peer.state.is_available() {
-			return None
-		}
-		peer.state = PeerSyncState::DownloadingStale(*hash);
-		Some(message::generic::BlockRequest {
-			id: 0,
-			fields: self.required_block_attributes.clone(),
-			from: message::FromBlock::Hash(*hash),
-			to: None,
-			direction: message::Direction::Ascending,
-			max: Some(1),
-		})
-	}
-
-	/// Download old block with unknown parent.
-	fn download_unknown_stale(&mut self, who: &PeerId, hash: &B::Hash) -> Option<BlockRequest<B>> {
-		let peer = self.peers.get_mut(who)?;
-		if !peer.state.is_available() {
-			return None
-		}
-		peer.state = PeerSyncState::DownloadingStale(*hash);
-		Some(message::generic::BlockRequest {
-			id: 0,
-			fields: self.required_block_attributes.clone(),
-			from: message::FromBlock::Hash(*hash),
-			to: None,
-			direction: message::Direction::Descending,
-			max: Some(MAX_UNKNOWN_FORK_DOWNLOAD_LEN),
-		})
-	}
-
 	/// Select a range of new blocks to download from the given peer.
 	fn select_new_blocks(&mut self, who: PeerId) -> Option<(Range<NumberFor<B>>, BlockRequest<B>)> {
 		// when there are too many blocks in the queue => do not try to download new blocks
@@ -1298,28 +1260,35 @@ fn peer_block_request<B: BlockT>(
 	}
 }
 
-/// Get pending explicit sync request for a peer.
-fn explicit_sync_request<B: BlockT>(
+/// Get pending fork sync targets for a peer.
+fn fork_sync_request<B: BlockT>(
 	id: &PeerId,
-	requests: &HashMap<B::Hash, SyncRequest<B>>,
+	targets: &HashMap<B::Hash, ForkTarget<B>>,
 	best_num: NumberFor<B>,
 	finalized: NumberFor<B>,
 	attributes: &message::BlockAttributes,
+	check_block: impl Fn(&B::Hash) -> BlockStatus,
 ) -> Option<(B::Hash, BlockRequest<B>)>
 {
-	for (hash, r) in requests {
+	for (hash, r) in targets {
 		if !r.peers.contains(id) {
 			continue
 		}
 		if r.number <= best_num {
 			trace!(target: "sync", "Downloading requested fork {:?} from {}", hash, id);
+			let parent_status = r.parent_hash.as_ref().map_or(BlockStatus::Unknown, check_block);
+			let mut count = (r.number - finalized).saturated_into::<u32>(); // up to the last finalized block
+			if parent_status != BlockStatus::Unknown {
+				// request only single block
+				count = 1;
+			}
 			return Some((hash.clone(), message::generic::BlockRequest {
 				id: 0,
 				fields: attributes.clone(),
 				from: message::FromBlock::Hash(hash.clone()),
 				to: None,
 				direction: message::Direction::Descending,
-				max: Some((r.number - finalized).saturated_into::<u32>()), // up to the last finalized block
+				max: Some(count),
 			}))
 		}
 	}