PQ84327: A NULLPOINTEREXCEPTION FROM THE SELECTIONMANAGER.POPSERVERFORINVOCATION METHOD IS THROWN UNDER HEAVY WORKLOADS

APAR status
Closed as program error.

Error description
WebSphere 5.0.1.
Under heavy workloads, a NullPointerException or
ConcurrentModificationException is thrown from a
WeakHashmap object in the Workload Management code.
The exception may look something like this:
Root exception is java.util.ConcurrentModificationException:
concurrent access to HashMap attempted by Thread Thread-7,5,
at java.util.HashMap.onExit(HashMap.java:175)
at java.util.HashMap.rehash(HashMap.java:347)
at java.util.HashMap.put(HashMap.java:418)
at java.util.WeakHashMap.put(WeakHashMap.java:298)
at com.ibm.ws.wlm.client.selection.SelectionManager.
pushServerForInvocat
at com.ibm.ws.wlm.client.selection.SelectionManager.
getTarget(SelectionM
.
This problem may also be seen with a threaddump.  You will see m
any threads in the following code:
.
"Thread-18628" daemon prio=5 tid=0x14a6528 nid=0x4bf5
runnable [0x193fe000..0x193ffc68]
at java.util.HashMap.get(HashMap.java:263)
at java.util.WeakHashMap.get(WeakHashMap.java:260)
at com.ibm.ws.wlm.client.selection.SelectionManager.getTarget
(SelectionManager.java:139)
at com.ibm.ws.wlm.client.WLMClient.getNextTarget(WLMClient.java:
Local fix Problem summary
****************************************************************
* USERS AFFECTED: WebSphere Application Server users of WLM,   *
*                 or Workload Management.                      *
****************************************************************
* PROBLEM DESCRIPTION: Under heavy workloads, a                *
*                      NullPointerException or                 *
*                      ConcurrentModificationException is      *
*                      thrown from a WeakHashmap object in     *
*                      the Workload Managment code.            *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
Under heavy workloads, a NullPointerException or
ConcurrentModificationException is thrown from a WeakHashmap
object in the Workload Management code.  The exception may look
something like this:

Root exception is java.util.ConcurrentModificationException:
concurrent access to HashMap attempted by Thread Thread-7,5,
at java.util.HashMap.onExit(HashMap.java:175)
at java.util.HashMap.rehash(HashMap.java:347)
at java.util.HashMap.put(HashMap.java:418)
at java.util.WeakHashMap.put(WeakHashMap.java:298)
at com.ibm.ws.wlm.client.selection.SelectionManager.
pushServerForInvocat
at com.ibm.ws.wlm.client.selection.SelectionManager.
getTarget(SelectionM
...
...
Problem conclusion
A synchronization block was needed to be placed around the
WeakHashmap in question.
Temporary fix
There is no temporary fix for this problem.
Comments
APAR information
APAR number PQ84327
Reported component name WAS NETWRK DEPL
Reported component ID 5630A3601
Reported release 00S
Status CLOSED PER
PE NoPE
HIPER NoHIPER
Special Attention NoSpecatt
Submitted date 2004-02-06
Closed date 2004-04-27
Last modified date 2004-04-27

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Modules/Macros
WLM          

Publications Referenced

Fix information

Applicable component levels
R003 PSY    UP
R00A PSY    UP
R00H PSY    UP
R00I PSY    UP
R00P PSY    UP
R00S PSY    UP
R00W PSY    UP
R103 PSY    UP
R10A PSY    UP
R10H PSY    UP
R10I PSY    UP
R10P PSY    UP
R10S PSY    UP
R10W PSY    UP


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > General
Operating system(s):
Software version: 00S
Software edition:
Reference #: PQ84327
IBM Group: Software Group
Modified date: Apr 27, 2004