Hi all, System: Tomcat 4.1.30 on Debian sarge java version "1.5.0_11" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_11-b03) Java HotSpot(TM) Client VM (build 1.5.0_11-b03, mixed mode, sharing)
in situations with high load, tomcat sometimes stops responding and is not able to recover from that status. In the catalina.out file, i get the following line: SEVERE: All threads (75) are currently busy, waiting. Increase maxThreads (75) or check the servlet status i searched some time in various forums and mailing list archives and found the following links: http://mail-archives.apache.org/mod_mbox/tomcat-users/200408.mbox/[EMAIL PROTECTED] http://marc.info/?l=tomcat-user&m=113297294417902&w=2 http://www.tek-tips.com/viewthread.cfm?qid=862552&page=3 http://www.mail-archive.com/[EMAIL PROTECTED]/msg127833.html Basically there seem to be 2 possible reasons for this behaviour 1. A bug (?) in Tomcat or the combination of JDK, glibc, whatever, which causes that tomcat does not recover from situations with too much requests. I could not find any information in the release notes of the Tomcat 4.1.x versions. 2. Some kind of deadlock or resource (database connections) availability problem which keeps the request handling threads from returning from the doPost/Get method. So i made a Threaddump using jstack (attached file). Most of the threads are in - java.lang.Object.wait(long) @bci=0 (Interpreted frame) - java.lang.Object.wait() @bci=2, line=474 (Interpreted frame) - org.apache.catalina.core.StandardWrapper.allocate() @bci=223, line=704 (Interpreted frame) but 19 threads are blocked in the bci 0 of the same static synchronized method called removeActiveRoles which is called from the doPost() method. - at.sonorys.dmc.utilities.ActiveRoleRemoval.removeActiveRoles(at.sonorys.dmc.utilities.DatabaseAccess, java.lang.String, java.lang.String, boolean) @bci=0 (Interpreted frame) - at.sonorys.dmc.CommDicora.CommHandleMessageSession.quitSession() @bci=23 (Interpreted frame) - at.sonorys.dmc.CommDicora.CommHandleMessageSession.doHandleSessionMsg() @bci=131 (Interpreted frame) - at.sonorys.dmc.CommDicora.CommHandleMessageSession.evalMessage() @bci=1 (Interpreted frame) - at.sonorys.dmc.CommDicora.CommDicoraServlet.doHandleMsg(javax.servlet.http.HttpServletResponse, javax.servlet.http.HttpServletRequest) @bci=103 (Interpreted frame) - at.sonorys.dmc.CommDicora.CommDicoraServlet.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) @bci=142 (Interpreted frame) The servlet implements the SingleThreadModel (not my decision). As you can see from the threaddump, all 19 threads are waiting to get into the same static synchronized method. I dont understand this because there must be one thread IN the method which holds the lock of the method? Is it possible for a thread to leave a synchronized method without returning the lock? br, Peter
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