> -----Original Message----- > From: Mark Thomas [mailto:ma...@apache.org] > Sent: Tuesday, October 22, 2013 3:32 AM > To: Tomcat Users List > Subject: Re: is the Tomcat-7 WsRemoteEndpointImplBase send methods > threadsafe, or should we be synchronizing until the Future<>.get() returns? > > On 22/10/2013 00:28, Bob DeRemer wrote: > > I'm trying to understand how Tomcat's outbound message processing > > works with respect to making multiple (concurrent) calls against a > > single RemoteEndpoint.Async using sendText/sendObject. Based on the > > ExecutionExceptions we got (see below), it seems that we should > > probably synchronize sends until the Future<>.get() returns, but I > > want to check with the community to be sure. I tried searching the > > javadocs of RemoteEndpoint.Async and associated interfaces, but could > > not find anything describing the threadsafe nature (existing or not). > > It appears that the spec lets the implementation determine how to > > handle stuff under the covers. This is fine, but we just need to > > understand what that means to multi-threaded code that wants to send > > messages. > > There was some discussion [1] in the EG on this point and the conclusion was > that the previous message had to complete before the next message was sent. > If you batching is used (which Tomcat supports) the semantics for complete > change but the previous message still has to complete before the next is sent. > > I've looked through the specification and I don't see this made clear > anywhere. > My experience of the J2EE EG's is that in cases like these following the > intention of the EG based on the mailing list archive is the way to go. > > > Looking at the Tomcat code, it looks like WsRemoteEndpointImplBase > > uses a static SendHandler (i.e. TextMessageSendHandler). > > That is a static definition of a class, not a static instance. A new instance > is > created for each message. > > > I noticed a > > little further down in the stack the logic does synchronize around a > > messagePartQueue, but this seems to be for handling parts of a single > > message. > > Correct. That is to ensure correct state management when different threads > are sending different parts of the message. > > > Otherwise, it looks like it doesn't expect another message to be sent > > until it's finished writing out. > > Correct. It should throw an exception if you try. > > > ExecutionException: In some recent testing of our client/server > > Endpoint(s) (using a locally built instance of Tomcat 7.0.48), we got > > ExecutionExceptions when sending messages concurrently without any > > delay. The errors started with a few Null Ptr(s), then were all > > wsRemoteEndpoint.inProgress (Message will not be sent because the > > WebSocket session is currently sending another message) > > > > Is my understanding correct, or am I missing something? Thanks in > > advance for any clarification. > > HTH, > > Mark
Great - thanks for the plumbing explanation! bob > > [1] > https://java.net/projects/websocket-spec/lists/jsr356-experts/archive/2013- > 02/message/1 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
