On 20.05.2009 00:53, Pantvaidya, Vishwajit wrote: >> -----Original Message----- >> From: Rainer Jung [mailto:rainer.j...@kippdata.de] >> Sent: Monday, May 18, 2009 11:10 PM >> To: Tomcat Users List >> Subject: Re: Running out of tomcat threads - why many threads in >> RUNNABLEstage even with no activity >> >> On 19.05.2009 02:54, Caldarale, Charles R wrote: >>>> From: Pantvaidya, Vishwajit [mailto:vpant...@selectica.com] >>>> Subject: RE: Running out of tomcat threads - why many threads in >>>> RUNNABLEstage even with no activity >>>> >>>> Ok - so then the question is when does tomcat transition the thread >>>> from Running to Waiting? Does that happen after AJP drops that >>>> connection? >> RUNNABLE and WAITING are thread states in the JVM. They don't relate in >> general to states inside Tomcat. In this special situation they do. >> >> The states you observe are both completely normal in themselves. One >> (the stack you abbreviate with RUNNABLE) is handling a persistant >> connection between web server and Tomcat which could send more requests, >> but at the moment no request is being processed, the other (you >> abbreviate with WAITING) is available to be associated with a new >> connection that might come in some time in the future. >> > > [Pantvaidya, Vishwajit] Thanks Rainer. The RUNNABLE thread - is it a > connection between Tomcat and webserver, or between Tomcat and AJP? Is it > still RUNNABLE and not WAITING because the servlet has not explicitly closed > the connection yet (something like HttpServletResponse.getOutputStresm.close)
The thread handles a connection betwen the web server and Tomcat. AJP is the protocol used on that connection. It is runnable, because a socket read from inside the JVM puts a thread into runnable state. The socket read is used to read the next request and will block until data arrives over the established connection. >>>> So could the problem be occurring here because AJP is holding on to >>>> connections? >>> Sorry, I haven't been following the thread that closely. Not sure >>> what the problem you're referring to actually is, but having a Tomcat >>> thread reading input from the AJP connector is pretty normal. >> The same to me. What's the problem? AJP is designed to reuse connections >> (use persistent connections). If you do not want them to be used for a >> very long time or like those connections to be closed when being idle, >> you have to configure the appropriate timeouts. Look at the timeouts >> documentation page of mod_jk. >> >> In general your max thread numbers in the web server layer and in the >> Tomcat AJP pool need to be set consistently. >> > > [Pantvaidya, Vishwajit] My problem is that tomcat is running out of threads > (maxthreadcount=200). My analysis of the issue is: > - threads count is exceeded because of a slow buildup of RUNNABLE threads > (and not because number of simultaneous http requests at some point exceeded > max thread count) I don't belibve this reason. I would say thread count is exceeded, because you allow a much higher concurrency on the web server layer. > - most/all newly created TP-Processor threads are in RUNNABLE state and > remain RUNNABLE - never go back to WAITING state (waiting for thread pool) So you are using persistent connections. There's no *problem* with that per se. If you ae uncomfortable with it configure the timeouts in the Tomcat connector *and* mod_jk. > - in such case, I find that tomcat spawns new threads when a new request > comes in "request" -> "connection" > - this continues and finally tomcat runs out of threads That's to simple, usually the "new requests" should be handled by existing Apache processes that already have a connection to Tomcat and will not create a new one. > - Setting connectionTimeout in server.xml seems to have resolved the issue - > but I am wondering if that was just a workaround i.e. whether so many threads > remaining RUNNABLE indicate a flaw in our webapp i.e. it not doing whatever's > necessary to close them and return them to WAITING state. No it is a misconifguration of your web server, mod_jk and Tomcat. The use of persistent AJP connections is opaque to the web application. Regards, Rainer --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
