I’m running tomcat 7 with apache 2.2 & mod_jk 1.2.26 on a debian-lenny x64 server with 2GB of RAM.
I’ve a strange problem with my server: every several hour & sometimes (under load) every several minutes, my tomcat ajp-connector pauses with a memory leak error, but seems this error also effects some other parts of system (e.g some other running applications also stop working) & I have to reboot the server to solve the problem for a while.
I’ve checked catalina.out for several days, but it seem’s there is not a unique error pattern just before pausing ajp with this message:
INFO: Pausing ProtocolHandler ["ajp-bio-8009"]
Sometimes there is this message before pausing:
Exception in thread "ajp-bio-8009-Acceptor-0" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Thread.java:597)...
& sometimes this one:
INFO: Reloading Context with name [] has started
Exception in thread "ContainerBackgroundProcessor[StandardEngine[Catalina]]" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Thread.java:597)
at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:5482)
at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:230)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3847)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:424)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1214)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1400)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1410)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1410)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1389)
at java.lang.Thread.run(Thread.java:619)
java.sql.SQLException: null, message from server: "Can't create a new thread (errno 11); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug"...
& some other times the output messages related to some other parts of program.
I’ve checked my application source code & I don’t guess it causes the problem, I’ve also checked memory usage using jConsole. The wanderfull point is that when server fails, is shows a lot of free memory on both heap & non-heap jvm memory space. As I told before, after crashing server, many other applications also fail & when I want to restart them it gives a resource temporary unavailable message (I’ve also checked my limits.conf file).
So I really really confused with this serious problem many days & i have really no more idea about it. So, can anybody please give me any kind of suggestion to solve this complicated & unknown problem ???
What could be the most possible reason for this error ?
I finally found the problem: it was not actually a memory leak, but the limitation in number of allowed threads for the VPS was caused the problem. My server was a Xen vps with default limitation of 256 threads, so when it reached the maximum allowed threads, the supervisor was killed some of running threads (that was cause of stopping some of my running processes). By increasing number of allowed threads to 512, the problem totally solved (of course if I increase maxThreads in tomcat settings, its obvious that the problem will rise again).