On 04/05/2011 15:20, Rainer Jung wrote: > I hope the following is not too long and confusing ...
Not at all. > On 03.05.2011 22:02, Mark Thomas wrote: >> Solution A >> ---------- >> NIO is designed to handle this using a poller. That isn't available to >> BIO so I attempted to simulate it. That generated excessive CPU load so >> I do not think simulated polling is the tight solution. > > I expect generating the SocketTimeoutException is expensive, because the > JVM has to generate the stack information. The rate of the Exception > when handling mostly keep-alive (extreme case) is your "poll" timeout > times the number of threads, e.g. 100ms timeout times 200 threads is > 2000 exceptions per second. Even if there is another reason for the high > CPU load, I expect it to be roughly proportional to the poll rate. <snip/> > Do we see a cpu time and thread blocking time efficient way of handling > many keep-alive connections? I don't see any API, that would help here. > Of course one could try to build a hyprid "blocking for normal > processing but non-blocking for keep-alive" thing, but since we already > have NIO I would also support recommending NIO for keep-alive. The only API I see is NIO and that is what the NIO connector is for. I don't see an efficient way to do this with the BIO API. > Switching the default from BIO to NIO is a big change, but only after we > switch will we find the last buglets and problems arising under rare > conditions. So if we want to switch, we should do it very soon. Doing it > late in the TC 7 cycle would be bad. I think we are beyond the point where we can change the default HTTP connector to NIO for Tomcat 7 (as much as part of me really, really wants to). > Lastly: APR uses server to server connections, as does HTTP when using a > reverse proxy in front of Tomcat. In those cases we have much fewer > connections with a higher rate of requests per connection. There > maxThreads == maxConnections is fine (and even the 75% rule could be > switched off). It is. The 75% limit only applies to the HTTP BIO connector. > So for this scenario it would be nice to not drop BIO, at > least until the major TC version after the default switched to NIO. We need a AJP-NIO connector first ;). Maybe an exercise for the upcoming Apache Retreat? The one huge advantage of AJP-NIO would be no need for aligning thread counts on httpd and Tomcat or messing about with timeouts etc to ensure connections <= maxThreads. As long as the *active* connections from httpd <= maxThreads, all would be fine. >> Solution B >> ---------- >> Return to the Tomcat 6 implementation where maxConnections == maxThreads. >> >> Additional clean-up >> ------------------- >> maxConnections is unnecessary in APR since pollerSize performs the same >> function. >> >> Summary >> ------- >> The proposed changes are: >> a) restore disabling keep-alive when threads used>= 75% of maxThreads >> b) remove maxConnections and associated code from the APR connector >> c) remove the configuration options for maxConnections from the BIO >> connector >> d) use maxThreads instead of maxConnections for the BIO connector >> e) update the docs > > I agree (especially after your additional clarifications in reply to > Konstantin). Great. I think we are heading towards a consensus. Mark --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For additional commands, e-mail: dev-h...@tomcat.apache.org
