Sync status refactoring (#5450)

As I was looking at the coupling between `SyncingEngine`,
`SyncingStrategy` and individual strategies I noticed a few things that
were unused, redundant or awkward.

The awkward change comes from
paritytech/substrate#13700 where
`num_connected_peers` property was added to `SyncStatus` struct just so
it can be rendered in the informer. While convenient, the property
didn't really belong there and was annoyingly set to `0` in some
strategies and to `num_peers` in others. I have replaced that with a
property on `SyncingService` that already stored necessary information
internally.

Also `ExtendedPeerInfo` didn't have a working `Clone` implementation due
to lack of perfect derive in Rust and while I ended up not using it in
the refactoring, I included fixed implementation for it in this PR
anyway.

While these changes are not strictly necessary for
#5333, they do reduce
coupling of syncing engine with syncing strategy, which I thought is a
good thing.

Reviewing individual commits will be the easiest as usual.

---------

Co-authored-by: Dmitry Markin <dmitry@markin.tech>

prdoc/pr_5450.prdoc

@@ -0,0 +1,18 @@
+title: Sync status refactoring
+
+doc:
+  - audience: Node Dev
+    description: |
+      `SyncingService` API in `sc-network-sync` has changed with some of the redundant methods related to sync status
+      removed that were mostly used internally or for testing purposes and is unlikely to impact external code.
+      `ExtendedPeerInfo` now has working `Clone` and `Copy` implementation.
+
+crates:
+  - name: sc-informant
+    bump: major
+  - name: sc-network-sync
+    bump: major
+  - name: sc-network-test
+    bump: major
+  - name: sc-service
+    bump: major

substrate/client/informant/src/display.rs

@@ -65,11 +65,11 @@ impl<B: BlockT> InformantDisplay<B> {
 		info: &ClientInfo<B>,
 		net_status: NetworkStatus,
 		sync_status: SyncStatus<B>,
+		num_connected_peers: usize,
 	) {
 		let best_number = info.chain.best_number;
 		let best_hash = info.chain.best_hash;
 		let finalized_number = info.chain.finalized_number;
-		let num_connected_peers = sync_status.num_connected_peers;
 		let speed = speed::<B>(best_number, self.last_number, self.last_update);
 		let total_bytes_inbound = net_status.total_bytes_inbound;
 		let total_bytes_outbound = net_status.total_bytes_outbound;

substrate/client/informant/src/lib.rs

@@ -24,7 +24,7 @@ use futures_timer::Delay;
 use log::{debug, info, trace};
 use sc_client_api::{BlockchainEvents, UsageProvider};
 use sc_network::NetworkStatusProvider;
-use sc_network_sync::SyncStatusProvider;
+use sc_network_sync::{SyncStatusProvider, SyncingService};
 use sp_blockchain::HeaderMetadata;
 use sp_runtime::traits::{Block as BlockT, Header};
 use std::{collections::VecDeque, fmt::Display, sync::Arc, time::Duration};
@@ -37,10 +37,9 @@ fn interval(duration: Duration) -> impl Stream<Item = ()> + Unpin {
 }
 
 /// Builds the informant and returns a `Future` that drives the informant.
-pub async fn build<B: BlockT, C, N, S>(client: Arc<C>, network: N, syncing: S)
+pub async fn build<B: BlockT, C, N>(client: Arc<C>, network: N, syncing: Arc<SyncingService<B>>)
 where
 	N: NetworkStatusProvider,
-	S: SyncStatusProvider<B>,
 	C: UsageProvider<B> + HeaderMetadata<B> + BlockchainEvents<B>,
 	<C as HeaderMetadata<B>>::Error: Display,
 {
@@ -52,13 +51,14 @@ where
 		.filter_map(|_| async {
 			let net_status = network.status().await;
 			let sync_status = syncing.status().await;
+			let num_connected_peers = syncing.num_connected_peers();
 
-			match (net_status.ok(), sync_status.ok()) {
-				(Some(net), Some(sync)) => Some((net, sync)),
+			match (net_status, sync_status) {
+				(Ok(net), Ok(sync)) => Some((net, sync, num_connected_peers)),
 				_ => None,
 			}
 		})
-		.for_each(move |(net_status, sync_status)| {
+		.for_each(move |(net_status, sync_status, num_connected_peers)| {
 			let info = client_1.usage_info();
 			if let Some(ref usage) = info.usage {
 				trace!(target: "usage", "Usage statistics: {}", usage);
@@ -68,7 +68,7 @@ where
 					"Usage statistics not displayed as backend does not provide it",
 				)
 			}
-			display.display(&info, net_status, sync_status);
+			display.display(&info, net_status, sync_status, num_connected_peers);
 			future::ready(())
 		});
 

substrate/client/network/sync/src/engine.rs

@@ -615,7 +615,6 @@ where
 			}
 
 			// Update atomic variables
-			self.num_connected.store(self.peers.len(), Ordering::Relaxed);
 			self.is_major_syncing.store(self.strategy.is_major_syncing(), Ordering::Relaxed);
 
 			// Process actions requested by a syncing strategy.
@@ -761,37 +760,20 @@ where
 				);
 			},
 			ToServiceCommand::Status(tx) => {
-				let mut status = self.strategy.status();
-				status.num_connected_peers = self.peers.len() as u32;
-				let _ = tx.send(status);
+				let _ = tx.send(self.strategy.status());
 			},
 			ToServiceCommand::NumActivePeers(tx) => {
 				let _ = tx.send(self.num_active_peers());
 			},
-			ToServiceCommand::SyncState(tx) => {
-				let _ = tx.send(self.strategy.status());
-			},
-			ToServiceCommand::BestSeenBlock(tx) => {
-				let _ = tx.send(self.strategy.status().best_seen_block);
-			},
-			ToServiceCommand::NumSyncPeers(tx) => {
-				let _ = tx.send(self.strategy.status().num_peers);
-			},
-			ToServiceCommand::NumQueuedBlocks(tx) => {
-				let _ = tx.send(self.strategy.status().queued_blocks);
-			},
 			ToServiceCommand::NumDownloadedBlocks(tx) => {
 				let _ = tx.send(self.strategy.num_downloaded_blocks());
 			},
 			ToServiceCommand::NumSyncRequests(tx) => {
 				let _ = tx.send(self.strategy.num_sync_requests());
 			},
 			ToServiceCommand::PeersInfo(tx) => {
-				let peers_info = self
-					.peers
-					.iter()
-					.map(|(peer_id, peer)| (*peer_id, peer.info.clone()))
-					.collect();
+				let peers_info =
+					self.peers.iter().map(|(peer_id, peer)| (*peer_id, peer.info)).collect();
 				let _ = tx.send(peers_info);
 			},
 			ToServiceCommand::OnBlockFinalized(hash, header) =>
@@ -867,6 +849,7 @@ where
 		if let Some(metrics) = &self.metrics {
 			metrics.peers.dec();
 		}
+		self.num_connected.fetch_sub(1, Ordering::AcqRel);
 
 		if self.important_peers.contains(&peer_id) {
 			log::warn!(target: LOG_TARGET, "Reserved peer {peer_id} disconnected");
@@ -1046,6 +1029,7 @@ where
 			if let Some(metrics) = &self.metrics {
 				metrics.peers.inc();
 			}
+			self.num_connected.fetch_add(1, Ordering::AcqRel);
 		}
 		self.peer_store_handle.set_peer_role(&peer_id, status.roles.into());
 

substrate/client/network/sync/src/service/syncing_service.rs

@@ -50,10 +50,6 @@ pub enum ToServiceCommand<B: BlockT> {
 	EventStream(TracingUnboundedSender<SyncEvent>),
 	Status(oneshot::Sender<SyncStatus<B>>),
 	NumActivePeers(oneshot::Sender<usize>),
-	SyncState(oneshot::Sender<SyncStatus<B>>),
-	BestSeenBlock(oneshot::Sender<Option<NumberFor<B>>>),
-	NumSyncPeers(oneshot::Sender<u32>),
-	NumQueuedBlocks(oneshot::Sender<u32>),
 	NumDownloadedBlocks(oneshot::Sender<usize>),
 	NumSyncRequests(oneshot::Sender<usize>),
 	PeersInfo(oneshot::Sender<Vec<(PeerId, ExtendedPeerInfo<B>)>>),
@@ -83,6 +79,11 @@ impl<B: BlockT> SyncingService<B> {
 		Self { tx, num_connected, is_major_syncing }
 	}
 
+	/// Get the number of peers known to `SyncingEngine` (both full and light).
+	pub fn num_connected_peers(&self) -> usize {
+		self.num_connected.load(Ordering::Relaxed)
+	}
+
 	/// Get the number of active peers.
 	pub async fn num_active_peers(&self) -> Result<usize, oneshot::Canceled> {
 		let (tx, rx) = oneshot::channel();
@@ -91,30 +92,6 @@ impl<B: BlockT> SyncingService<B> {
 		rx.await
 	}
 
-	/// Get best seen block.
-	pub async fn best_seen_block(&self) -> Result<Option<NumberFor<B>>, oneshot::Canceled> {
-		let (tx, rx) = oneshot::channel();
-		let _ = self.tx.unbounded_send(ToServiceCommand::BestSeenBlock(tx));
-
-		rx.await
-	}
-
-	/// Get the number of sync peers.
-	pub async fn num_sync_peers(&self) -> Result<u32, oneshot::Canceled> {
-		let (tx, rx) = oneshot::channel();
-		let _ = self.tx.unbounded_send(ToServiceCommand::NumSyncPeers(tx));
-
-		rx.await
-	}
-
-	/// Get the number of queued blocks.
-	pub async fn num_queued_blocks(&self) -> Result<u32, oneshot::Canceled> {
-		let (tx, rx) = oneshot::channel();
-		let _ = self.tx.unbounded_send(ToServiceCommand::NumQueuedBlocks(tx));
-
-		rx.await
-	}
-
 	/// Get the number of downloaded blocks.
 	pub async fn num_downloaded_blocks(&self) -> Result<usize, oneshot::Canceled> {
 		let (tx, rx) = oneshot::channel();
@@ -149,11 +126,11 @@ impl<B: BlockT> SyncingService<B> {
 	/// Get sync status
 	///
 	/// Returns an error if `SyncingEngine` has terminated.
-	pub async fn status(&self) -> Result<SyncStatus<B>, ()> {
+	pub async fn status(&self) -> Result<SyncStatus<B>, oneshot::Canceled> {
 		let (tx, rx) = oneshot::channel();
 		let _ = self.tx.unbounded_send(ToServiceCommand::Status(tx));
 
-		rx.await.map_err(|_| ())
+		rx.await
 	}
 }
 

substrate/client/network/sync/src/strategy/chain_sync.rs

@@ -438,7 +438,6 @@ where
 			state: sync_state,
 			best_seen_block,
 			num_peers: self.peers.len() as u32,
-			num_connected_peers: 0u32,
 			queued_blocks: self.queue_blocks.len() as u32,
 			state_sync: self.state_sync.as_ref().map(|s| s.progress()),
 			warp_sync: warp_sync_progress,

substrate/client/network/sync/src/strategy/state.rs

@@ -340,7 +340,6 @@ impl<B: BlockT> StateStrategy<B> {
 			},
 			best_seen_block: Some(self.state_sync.target_number()),
 			num_peers: self.peers.len().saturated_into(),
-			num_connected_peers: self.peers.len().saturated_into(),
 			queued_blocks: 0,
 			state_sync: Some(self.state_sync.progress()),
 			warp_sync: None,

substrate/client/network/sync/src/strategy/warp.rs

@@ -576,7 +576,6 @@ where
 				Phase::Complete => None,
 			},
 			num_peers: self.peers.len().saturated_into(),
-			num_connected_peers: self.peers.len().saturated_into(),
 			queued_blocks: 0,
 			state_sync: None,
 			warp_sync: Some(self.progress()),

substrate/client/network/sync/src/types.rs

@@ -39,7 +39,7 @@ pub struct PeerInfo<Block: BlockT> {
 }
 
 /// Info about a peer's known state (both full and light).
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct ExtendedPeerInfo<B: BlockT> {
 	/// Roles
 	pub roles: Roles,
@@ -49,6 +49,17 @@ pub struct ExtendedPeerInfo<B: BlockT> {
 	pub best_number: NumberFor<B>,
 }
 
+impl<B> Clone for ExtendedPeerInfo<B>
+where
+	B: BlockT,
+{
+	fn clone(&self) -> Self {
+		Self { roles: self.roles, best_hash: self.best_hash, best_number: self.best_number }
+	}
+}
+
+impl<B> Copy for ExtendedPeerInfo<B> where B: BlockT {}
+
 /// Reported sync state.
 #[derive(Clone, Eq, PartialEq, Debug)]
 pub enum SyncState<BlockNumber> {
@@ -76,8 +87,6 @@ pub struct SyncStatus<Block: BlockT> {
 	pub best_seen_block: Option<NumberFor<Block>>,
 	/// Number of peers participating in syncing.
 	pub num_peers: u32,
-	/// Number of peers known to `SyncingEngine` (both full and light).
-	pub num_connected_peers: u32,
 	/// Number of blocks queued for import
 	pub queued_blocks: u32,
 	/// State sync status in progress, if any.

substrate/client/network/test/src/lib.rs

@@ -266,7 +266,7 @@ where
 
 	/// Returns the number of peers we're connected to.
 	pub async fn num_peers(&self) -> usize {
-		self.sync_service.status().await.unwrap().num_connected_peers as usize
+		self.sync_service.num_connected_peers()
 	}
 
 	/// Returns the number of downloaded blocks.
@@ -1016,7 +1016,7 @@ pub trait TestNetFactory: Default + Sized + Send {
 
 		for peer in peers {
 			if peer.sync_service.is_major_syncing() ||
-				peer.sync_service.num_queued_blocks().await.unwrap() != 0
+				peer.sync_service.status().await.unwrap().queued_blocks != 0
 			{
 				return false
 			}
@@ -1036,7 +1036,7 @@ pub trait TestNetFactory: Default + Sized + Send {
 	async fn is_idle(&mut self) -> bool {
 		let peers = self.peers_mut();
 		for peer in peers {
-			if peer.sync_service.num_queued_blocks().await.unwrap() != 0 {
+			if peer.sync_service.status().await.unwrap().queued_blocks != 0 {
 				return false
 			}
 			if peer.sync_service.num_sync_requests().await.unwrap() != 0 {
@@ -1094,9 +1094,7 @@ pub trait TestNetFactory: Default + Sized + Send {
 
 		'outer: loop {
 			for sync_service in &sync_services {
-				if sync_service.status().await.unwrap().num_connected_peers as usize !=
-					num_peers - 1
-				{
+				if sync_service.num_connected_peers() != num_peers - 1 {
 					futures::future::poll_fn::<(), _>(|cx| {
 						self.poll(cx);
 						Poll::Ready(())

substrate/client/network/test/src/sync.rs

@@ -1049,7 +1049,7 @@ async fn syncs_all_forks_from_single_peer() {
 		})
 		.await;
 
-		if net.peer(1).sync_service().best_seen_block().await.unwrap() == Some(12) {
+		if net.peer(1).sync_service().status().await.unwrap().best_seen_block == Some(12) {
 			break
 		}
 	}

substrate/client/service/src/lib.rs

@@ -341,7 +341,7 @@ pub async fn build_system_rpc_future<
 			sc_rpc::system::Request::SyncState(sender) => {
 				use sc_rpc::system::SyncState;
 
-				match sync_service.best_seen_block().await {
+				match sync_service.status().await.map(|status| status.best_seen_block) {
 					Ok(best_seen_block) => {
 						let best_number = client.info().best_number;
 						let _ = sender.send(SyncState {