On 30/12/2012 22:20, Mark Thomas wrote: > On 24/12/2012 11:17, ma...@apache.org wrote: >> Author: markt >> Date: Mon Dec 24 11:17:51 2012 >> New Revision: 1425633 >> >> URL: http://svn.apache.org/viewvc?rev=1425633&view=rev >> Log: >> Allow multiple threads to process an upgraded connection at the same time. >> This is required to support blocking reads/writes. The >> Servlet[Input|Output]Streams do not expose an API for a blocking >> [read|write]. Therefore to block a thread has to wait until >> [onDataAvailable()|onWritePossible()] is called. The problem is that the >> waiting thread holds a lock on the socket and there is no way through the >> Servlet 3.1 API to release that lock. Until the lock is released the thread >> that will eventually call [onDataAvailable()|onWritePossible()] is blocked. >> So a form of deadlock occurs. To overcome this without requiring libraries >> such as WebSocket implementations to access container specific APIs, Tomcat >> has to allow multiple threads to process a upgraded connection at the same >> time. > > While this worked on Windows XP, it doesn't work on Linux which - from > memory of running the Autobahn tests on the Tomcat 7.0.x web socket > implementation - has a much better (i.e. faster) network implementation. > > The issue is that the Servlet 3.1 non-blocking proposal requires > multiple container managed threads to be using the socket at the same > time. I think this is limited to two threads (one reading, one writing) > but the specification does not explicitly state that so there may be a > requirement for more. I will be starting a discussion in the EG on this > point. Regardless, prior to this commit Tomcat enforced a one socket - > one thread limit and that limit will need to be removed in Tomcat 8. > > Some form of re-factoring will be required but before I embark any > further down that road I want to take some time to review and fully > understand the existing code. There are various parts that would benefit > from some additional commentary and I suspect that a little clean-up > will be possible as well.
During the refactoring, I found a handful of threading issues. Fixing those appears to have fixed the Autobahn testsuite for Linux. I still intend to continue with investigating the refactoring as I am still not really happy with the above commit. Mark --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For additional commands, e-mail: dev-h...@tomcat.apache.org
