Handle telemetry socket errors (#3321)

* Handle telemetry socket errors

* Line width

substrate/core/telemetry/src/worker/node.rs

@@ -87,7 +87,11 @@ impl<TTrans: Transport> Node<TTrans> {
 
 impl<TTrans: Transport, TSinkErr> Node<TTrans>
 where TTrans: Clone + Unpin, TTrans::Dial: Unpin,
-	TTrans::Output: Sink<BytesMut, Error = TSinkErr> + Stream + Unpin, TSinkErr: fmt::Debug {
+	TTrans::Output: Sink<BytesMut, Error = TSinkErr>
+		+ Stream<Item=Result<BytesMut, TSinkErr>>
+		+ Unpin,
+	TSinkErr: fmt::Debug
+{
 	/// Sends a WebSocket frame to the node. Returns an error if we are not connected to the node.
 	///
 	/// After calling this method, you should call `poll` in order for it to be properly processed.
@@ -175,7 +179,10 @@ fn gen_rand_reconnect_delay() -> Delay {
 }
 
 impl<TTrans: Transport, TSinkErr> NodeSocketConnected<TTrans>
-where TTrans::Output: Sink<BytesMut, Error = TSinkErr> + Stream + Unpin {
+where TTrans::Output: Sink<BytesMut, Error = TSinkErr>
+	+ Stream<Item=Result<BytesMut, TSinkErr>>
+	+ Unpin
+{
 	/// Processes the queue of messages for the connected socket.
 	///
 	/// The address is passed for logging purposes only.
@@ -208,13 +215,18 @@ where TTrans::Output: Sink<BytesMut, Error = TSinkErr> + Stream + Unpin {
 					Poll::Ready(Ok(())) => self.need_flush = false,
 				}
 
-			} else if let Poll::Ready(_) = Stream::poll_next(Pin::new(&mut self.sink), cx) {
-				// We poll the telemetry `Stream` because the underlying implementation relies on
-				// this in order to answer PINGs.
-				// We don't do anything with incoming messages, however.
-
 			} else {
-				break
+				match Stream::poll_next(Pin::new(&mut self.sink), cx) {
+					Poll::Ready(Some(Ok(_))) => {
+						// We poll the telemetry `Stream` because the underlying implementation relies on
+						// this in order to answer PINGs.
+						// We don't do anything with incoming messages, however.
+					},
+					Poll::Ready(Some(Err(err))) => {
+						return Poll::Ready(Err(err))
+					},
+					Poll::Pending | Poll::Ready(None) => break,
+				}
 			}
 		}