https://issues.apache.org/bugzilla/show_bug.cgi?id=46193
Summary: Potential Thread problem with SessionManager
Product: Tomcat 6
Version: 6.0.16
Platform: PC
OS/Version: Windows XP
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
AssignedTo: dev@tomcat.apache.org
ReportedBy: [EMAIL PROTECTED]
Hi to all,
Under heavly load (about 500k/requests by day), I see this error about
30 times last week on a Tomcat 6.0.16 (with libtcnative 1.1.14 on a
Suse SLES 10 and IBM JDK 1.6-jvmxi3260-20080415_18762).
We have many HTTP sessions on our application and so frequent session cleanup
done by Tomcat.
We see theses errors :
WARNING: Exception processing manager
[EMAIL PROTECTED] background
process
Throwable occurred: java.lang.ArrayIndexOutOfBoundsException
at java.util.AbstractCollection.toArray(Unknown Source)
at
org.apache.catalina.session.ManagerBase.findSessions(ManagerBase.java:873)
at
org.apache.catalina.session.ManagerBase.processExpires(ManagerBase.java:676)
at
org.apache.catalina.session.ManagerBase.backgroundProcess(ManagerBase.java:667)
at
org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1316)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
at java.lang.Thread.run(Thread.java:735)
7 nov. 2008 16:18:21 org.apache.catalina.core.ContainerBase backgroundProcess
---
WARNING: Exception processing manager
[EMAIL PROTECTED] background
process
Throwable occurred: java.lang.IllegalMonitorStateException
at
java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:140)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1188)
at
java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:444)
at
java.util.concurrent.ConcurrentHashMap$Segment.remove(ConcurrentHashMap.java:555)
at
java.util.concurrent.ConcurrentHashMap.remove(ConcurrentHashMap.java:936)
at org.apache.catalina.session.ManagerBase.remove(ManagerBase.java:885)
at
org.apache.catalina.session.StandardSession.expire(StandardSession.java:743)
at
org.apache.catalina.session.StandardSession.isValid(StandardSession.java:592)
at
org.apache.catalina.session.ManagerBase.processExpires(ManagerBase.java:682)
at
org.apache.catalina.session.ManagerBase.backgroundProcess(ManagerBase.java:667)
at
org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1316)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
at java.lang.Thread.run(Thread.java:735)
We take a look at ManagerBase and the sessions is using ConcurrentHashMap.
We wonder if they couldn't be some Concurrency problems when some threads are
updating the sessions Map while ManagerBase try to dump the sessions into
sessions array in findSessions.
>From ConcurrentHashMap comments :
* Enumerations return elements reflecting the state of the hash table
* at some point at or since the creation of the iterator/enumeration.
* They do <em>not</em> throw
* [EMAIL PROTECTED] ConcurrentModificationException}. However, iterators are
* designed to be used by only one thread at a time.
Regards
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