Hi, > -----Original Message----- > From: Mark Thomas [mailto:ma...@apache.org] > Sent: Thursday, August 27, 2015 12:30 AM > To: Tomcat Users List <users@tomcat.apache.org> > Subject: Re: AW: WebSocket asynchronous reads > > On 26/08/2015 12:50, Steffen Heil (Mailinglisten) wrote: > > Hi > > > > > >>> Is there a way to tell tomcat to stop receiving data for a certain > >>> websocket? > >>> (Not to close it, but not to read from inputstream for some time.) > > > > > >> Sorry, no. > >> The best you can do is a no-op branch in the message handler. > > > > > > Which means I have to either buffer all incoming messages until I am ready > to process them (might occupy lots of memory) or I have to drop them. > > Both is not really ideal. > > > > I don’t know, if the websocket specification already defines something, but > are there any plans to implement such a feature? > > Nothing comes to mind. Sounds like what you really want is reactive streams. > > > From my POV it would be rather easy not to unregister a certain connection > in the read selector and reregister it later on. > > However such an API would need to exposed somehow. > > Yes, but such low level access doesn't seem right to me.
I've also thought about that limitation in the Java Websocket API in the past. I could imagine to use some form of sleep/wait (e.g. Semaphore.aquire()) in the onMessage method to block the thread until it should continue reading. However that would of course contradict the aim of asynchronous/non-blocking I/O to not block threads while waiting for data. This is where I like the .Net WebSocket API [1] that is a bit lower-level: It provides ReceiveAsync() and SendAsync() methods that allow you to specify when you actually want to read from the websocket connection without blocking a thread (the ASP.Net API also allows the code in the HTTP pipeline to decide if and when a WebSocket/Upgrade request is accepted). (This could also be useful for forwarding Websocket connections from IIS to Tomcat which currently isn't supported by the ISAPI Redirector and the AJP protocol - I had been working on a C# SPDY redirector module for IIS but haven't yet found time to update it to use HTTP/2 and base it on the new modular ASP.Net 5 runtime [2] which will also be officially supported by MS for Linux and OS X). I don't have knowledge about NIO in Java, but for extending the current API I could imagine some startReceive() method (as a counterpart to RemoteEndpoint.Async#sendText()) using a sort of callback or just raising the onMessage event of the Endpoint as before when data has received (but I suppose there are better approaches). Regards, Konstantin Preißer [1] https://msdn.microsoft.com/de-de/library/system.net.websockets.websocket(v=vs.110).aspx [2] https://github.com/aspnet/home --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
