Refactor Sync status updates into a stream of updates (#1858)

* refactor sync provider

* relative use of interval

* typo

* set propagate timeout to 2500ms

* address comments

* fix instant calc

* update intervals

substrate/core/rpc/src/system/mod.rs

@@ -109,10 +109,9 @@ impl<B: traits::Block> SystemApi<B::Hash, <B::Header as HeaderT>::Number> for Sy
 	}
 
 	fn system_health(&self) -> Result<Health> {
-		let status = self.sync.status();
 		Ok(Health {
-			peers: status.num_peers,
-			is_syncing: status.sync.is_major_syncing(),
+			peers: self.sync.peers().len(),
+			is_syncing: self.sync.is_major_syncing(),
 			should_have_peers: self.should_have_peers,
 		})
 	}

substrate/core/rpc/src/system/tests.rs

@@ -16,10 +16,11 @@
 
 use super::*;
 
-use network::{self, SyncState, SyncStatus, ProtocolStatus, NodeIndex, PeerId, PeerInfo as NetworkPeerInfo};
+use network::{self, ProtocolStatus, NodeIndex, PeerId, PeerInfo as NetworkPeerInfo};
 use network::config::Roles;
 use test_client::runtime::Block;
 use assert_matches::assert_matches;
+use futures::sync::mpsc;
 
 struct Status {
 	pub peers: usize,
@@ -40,16 +41,9 @@ impl Default for Status {
 }
 
 impl network::SyncProvider<Block> for Status {
-	fn status(&self) -> ProtocolStatus<Block> {
-		ProtocolStatus {
-			sync: SyncStatus {
-				state: if self.is_syncing { SyncState::Downloading } else { SyncState::Idle },
-				best_seen_block: None,
-				num_peers: self.peers as u32,
-			},
-			num_peers: self.peers,
-			num_active_peers: 0,
-		}
+	fn status(&self) -> mpsc::UnboundedReceiver<ProtocolStatus<Block>> {
+		let (_sink, stream) = mpsc::unbounded();
+		stream
 	}
 
 	fn network_state(&self) -> network::NetworkState {
@@ -67,13 +61,23 @@ impl network::SyncProvider<Block> for Status {
 	}
 
 	fn peers(&self) -> Vec<(NodeIndex, NetworkPeerInfo<Block>)> {
-		vec![(1, NetworkPeerInfo {
-			peer_id: self.peer_id.clone(),
-			roles: Roles::FULL,
-			protocol_version: 1,
-			best_hash: Default::default(),
-			best_number: 1
-		})]
+		let mut peers = vec![];
+		for _peer in 0..self.peers {
+			peers.push(
+				(1, NetworkPeerInfo {
+					peer_id: self.peer_id.clone(),
+					roles: Roles::FULL,
+					protocol_version: 1,
+					best_hash: Default::default(),
+					best_number: 1
+				})
+			);
+		}
+		peers
+	}
+
+	fn is_major_syncing(&self) -> bool {
+		self.is_syncing
 	}
 }