Details
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Improvement
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Status: Closed
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Major
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Resolution: Fixed
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7.2.0
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None
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Tomcat 7.0.59, java8
Description
Recently I ran into a strange error in our Wicket application that uses Wicket's native WebSockets:
java.lang.IllegalStateException: The remote endpoint was in state [TEXT_FULL_WRITING] which is an invalid state for called method
at org.apache.tomcat.websocket.WsRemoteEndpointImplBase$StateMachine.checkState(WsRemoteEndpointImplBase.java:1175)
at org.apache.tomcat.websocket.WsRemoteEndpointImplBase$StateMachine.textStart(WsRemoteEndpointImplBase.java:1138)
at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendString(WsRemoteEndpointImplBase.java:192)
at org.apache.tomcat.websocket.WsRemoteEndpointBasic.sendText(WsRemoteEndpointBasic.java:37)
at org.apache.wicket.protocol.ws.javax.JavaxWebSocketConnection.sendMessage(JavaxWebSocketConnection.java:81)
at org.apache.wicket.protocol.ws.api.WebSocketResponse.close(WebSocketResponse.java:92)
at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor.broadcastMessage(AbstractWebSocketProcessor.java:252)
at org.apache.wicket.protocol.ws.api.AbstractWebSocketConnection.sendMessage(AbstractWebSocketConnection.java:43)
...
As far as I understand the problem, we are trying to send more messages through one connection at the same time. Since we push messages on connections from background services/threads, this is very likely.
Looking at the JSR 356 API I was found that
If the websocket connection underlying this RemoteEndpoint is busy sending a message when a call is made to send another one, for example if two threads attempt to call a send method concurrently, or if a developer attempts to send a new message while in the middle of sending an existing one, the send method called while the connection is already busy may throw an IllegalStateException.
I think that using synchronized versions of JavaxWebSocketConnection.sendMessage.. methods would be great idea.