Fix unstable peers and slowness in sync (#9967)

* Don't sync all peers after each response

* Update formating

* Fix tests: add `continue_sync` to `Sync_step`

* Update ethcore/sync/src/chain/mod.rs

Co-Authored-By: ngotchac <ngotchac@gmail.com>

ethcore/sync/src/api.rs

@@ -420,9 +420,10 @@ impl SyncProvider for EthSync {
 }
 
 const PEERS_TIMER: TimerToken = 0;
-const SYNC_TIMER: TimerToken = 1;
+const MAINTAIN_SYNC_TIMER: TimerToken = 1;
-const TX_TIMER: TimerToken = 2;
+const CONTINUE_SYNC_TIMER: TimerToken = 2;
-const PRIORITY_TIMER: TimerToken = 3;
+const TX_TIMER: TimerToken = 3;
+const PRIORITY_TIMER: TimerToken = 4;
 
 pub(crate) const PRIORITY_TIMER_INTERVAL: Duration = Duration::from_millis(250);
 
@@ -441,7 +442,8 @@ impl NetworkProtocolHandler for SyncProtocolHandler {
 	fn initialize(&self, io: &NetworkContext) {
 		if io.subprotocol_name() != WARP_SYNC_PROTOCOL_ID {
 			io.register_timer(PEERS_TIMER, Duration::from_millis(700)).expect("Error registering peers timer");
-			io.register_timer(SYNC_TIMER, Duration::from_millis(1100)).expect("Error registering sync timer");
+			io.register_timer(MAINTAIN_SYNC_TIMER, Duration::from_millis(1100)).expect("Error registering sync timer");
+			io.register_timer(CONTINUE_SYNC_TIMER, Duration::from_millis(2500)).expect("Error registering sync timer");
 			io.register_timer(TX_TIMER, Duration::from_millis(1300)).expect("Error registering transactions timer");
 
 			io.register_timer(PRIORITY_TIMER, PRIORITY_TIMER_INTERVAL).expect("Error registering peers timer");
@@ -474,7 +476,8 @@ impl NetworkProtocolHandler for SyncProtocolHandler {
 		let mut io = NetSyncIo::new(io, &*self.chain, &*self.snapshot_service, &self.overlay);
 		match timer {
 			PEERS_TIMER => self.sync.write().maintain_peers(&mut io),
-			SYNC_TIMER => self.sync.write().maintain_sync(&mut io),
+			MAINTAIN_SYNC_TIMER => self.sync.write().maintain_sync(&mut io),
+			CONTINUE_SYNC_TIMER => self.sync.write().continue_sync(&mut io),
 			TX_TIMER => self.sync.write().propagate_new_transactions(&mut io),
 			PRIORITY_TIMER => self.sync.process_priority_queue(&mut io),
 			_ => warn!("Unknown timer {} triggered.", timer),

ethcore/sync/src/chain/handler.rs

@@ -97,8 +97,6 @@ impl SyncHandler {
 				sync.sync_peer(io, peer, false);
 			},
 		}
-		// give tasks to other peers
-		sync.continue_sync(io);
 	}
 
 	/// Called when peer sends us new consensus packet

ethcore/sync/src/chain/mod.rs

@@ -866,32 +866,29 @@ impl ChainSync {
 	}
 
 	/// Resume downloading
-	fn continue_sync(&mut self, io: &mut SyncIo) {
+	pub fn continue_sync(&mut self, io: &mut SyncIo) {
+		if self.state == SyncState::Waiting {
+			trace!(target: "sync", "Waiting for the block queue");
+		} else if self.state == SyncState::SnapshotWaiting {
+			trace!(target: "sync", "Waiting for the snapshot restoration");
+		} else {
 			// Collect active peers that can sync
-		let confirmed_peers: Vec<(PeerId, u8)> = self.peers.iter().filter_map(|(peer_id, peer)|
+			let mut peers: Vec<(PeerId, u8)> = self.peers.iter().filter_map(|(peer_id, peer)|
-			if peer.can_sync() {
+				if peer.can_sync() && peer.asking == PeerAsking::Nothing && self.active_peers.contains(&peer_id) {
 					Some((*peer_id, peer.protocol_version))
 				} else {
 					None
 				}
 			).collect();
 
+			if peers.len() > 0 {
 				trace!(
 					target: "sync",
-			"Syncing with peers: {} active, {} confirmed, {} total",
+					"Syncing with peers: {} active, {} available, {} total",
-			self.active_peers.len(), confirmed_peers.len(), self.peers.len()
+					self.active_peers.len(), peers.len(), self.peers.len()
 				);
 
-		if self.state == SyncState::Waiting {
+				random::new().shuffle(&mut peers); // TODO (#646): sort by rating
-			trace!(target: "sync", "Waiting for the block queue");
-		} else if self.state == SyncState::SnapshotWaiting {
-			trace!(target: "sync", "Waiting for the snapshot restoration");
-		} else {
-			let mut peers: Vec<(PeerId, u8)> = confirmed_peers.iter().filter(|&&(peer_id, _)|
-				self.active_peers.contains(&peer_id)
-			).map(|v| *v).collect();
-
-			random::new().shuffle(&mut peers); //TODO: sort by rating
 				// prefer peers with higher protocol version
 				peers.sort_by(|&(_, ref v1), &(_, ref v2)| v1.cmp(v2));
 
@@ -899,6 +896,7 @@ impl ChainSync {
 					self.sync_peer(io, peer_id, false);
 				}
 			}
+		}
 
 		if
 			(self.state == SyncState::Blocks || self.state == SyncState::NewBlocks) &&

ethcore/sync/src/tests/helpers.rs

@@ -286,10 +286,12 @@ impl<C: FlushingBlockChainClient> Peer for EthPeer<C> {
 	}
 
 	fn sync_step(&self) {
+		let mut io = TestIo::new(&*self.chain, &self.snapshot_service, &self.queue, None);
 		self.chain.flush();
-		self.sync.write().maintain_peers(&mut TestIo::new(&*self.chain, &self.snapshot_service, &self.queue, None));
+		self.sync.write().maintain_peers(&mut io);
-		self.sync.write().maintain_sync(&mut TestIo::new(&*self.chain, &self.snapshot_service, &self.queue, None));
+		self.sync.write().maintain_sync(&mut io);
-		self.sync.write().propagate_new_transactions(&mut TestIo::new(&*self.chain, &self.snapshot_service, &self.queue, None));
+		self.sync.write().continue_sync(&mut io);
+		self.sync.write().propagate_new_transactions(&mut io);
 	}
 
 	fn restart_sync(&self) {