Improve shutdown responsiveness of SubProtocolWSH

Proactively notify all active WebSocket sessions when a shutdown is
progress. Sessions then can ignore further attempts to send messages
and also stop stop trying to flush messages right away.

spring-websocket/src/main/java/org/springframework/web/socket/handler/ConcurrentWebSocketSessionDecorator.java

@@ -18,7 +18,6 @@ package org.springframework.web.socket.handler;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.springframework.util.Assert;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.WebSocketMessage;
 import org.springframework.web.socket.WebSocketSession;
@@ -62,6 +61,8 @@ public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorat
 
 	private volatile boolean limitExceeded;
 
+	private volatile boolean shutDownInProgress;
+
 
 	private final Lock flushLock = new ReentrantLock();
 
@@ -87,7 +88,7 @@ public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorat
 
 	public void sendMessage(WebSocketMessage<?> message) throws IOException {
 
-		if (this.limitExceeded) {
+		if (isDisabled()) {
 			return;
 		}
 
@@ -105,15 +106,19 @@ public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorat
 				break;
 			}
 		}
-		while (!this.buffer.isEmpty());
+		while (!this.buffer.isEmpty() && !isDisabled());
+	}
+
+	private boolean isDisabled() {
+		return (this.limitExceeded || this.shutDownInProgress);
 	}
 
 	private boolean tryFlushMessageBuffer() throws IOException {
-		if (this.flushLock.tryLock() && !this.limitExceeded) {
+		if (this.flushLock.tryLock()) {
 			try {
 				while (true) {
 					WebSocketMessage<?> messageToSend = this.buffer.poll();
-					if (messageToSend == null) {
+					if (messageToSend == null || isDisabled()) {
 						break;
 					}
 					this.bufferSize.addAndGet(messageToSend.getPayloadLength() * -1);
@@ -132,7 +137,7 @@ public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorat
 	}
 
 	private void checkSessionLimits() throws IOException {
-		if (this.closeLock.tryLock() && !this.limitExceeded) {
+		if (!isDisabled() && this.closeLock.tryLock()) {
 			try {
 				if (getTimeSinceSendStarted() > this.sendTimeLimit) {
 
@@ -161,4 +166,9 @@ public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorat
 		throw new SessionLimitExceededException(reason, status);
 	}
 
+	@Override
+	public void close(CloseStatus status) throws IOException {
+		this.shutDownInProgress = true;
+		super.close(status);
+	}
 }

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SubProtocolWebSocketHandler.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.socket.messaging;
 
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashSet;
@@ -221,8 +222,19 @@ public class SubProtocolWebSocketHandler implements WebSocketHandler,
 	@Override
 	public final void stop() {
 		synchronized (this.lifecycleMonitor) {
+
 			this.running = false;
 			this.clientOutboundChannel.unsubscribe(this);
+
+			// Notify sessions to stop flushing messages
+			for (WebSocketSession session : this.sessions.values()) {
+				try {
+					session.close(CloseStatus.GOING_AWAY);
+				}
+				catch (Throwable t) {
+					logger.error("Failed to close session id '" + session.getId() + "': " + t.getMessage());
+				}
+			}
 		}
 	}
 
@@ -298,7 +310,7 @@ public class SubProtocolWebSocketHandler implements WebSocketHandler,
 
 		WebSocketSession session = this.sessions.get(sessionId);
 		if (session == null) {
-			logger.error("Session not found for session with id " + sessionId);
+			logger.error("Session not found for session with id '" + sessionId + "', ignoring message " + message);
 			return;
 		}