PK96150: MESSAGE DELIVERY FOR JMS CONSUMERS USING READAHEAD STOPS INTERMITTENTLY.

Fixes are available

APAR status

Closed as program error.

Error description

A Service Integration Bus (SIB) application with multiple JMS
consumers using readahead using onMessage to receive messages
experiences problems receiving messages.  Message delivery
stops.  This happens intermittently throughout the day, first
with one consumer and then it spreads to others.

Thread dumps gathered from the JVM when these subscribers are
stuck show many threads locked in the deliverMessages method:

at
com/ibm/ws/sib/comms/client/proxyqueue/impl/AsynchConsumerProxyQ
ueueImpl.deliverMessages(AsynchConsumerProxyQueueImpl.java

Local fix

```
Restart client.
```

Problem summary

****************************************************************
* USERS AFFECTED:  Users of the default messaging provider for *
*                  IBM WebSphere Application Server            *
*                  Version 6.1 and Version 7.0                 *
****************************************************************
* PROBLEM DESCRIPTION: Delays consuming messages in one        *
*                      asynchronous consumer with              *
*                      read-ahead enabled, might cause         *
*                      delays delivering messages              *
*                      to other consumers in the same JVM,     *
*                      even when theasynchronous consumer      *
*                      thread pool is sufficiently large       *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
The issue described in this APAR affects JMS applications with
multiple consumers running in a single client JVM consuming
from destinations asynchronously (using a message listener)
with read-ahead enabled.

When one of these consumers is slow to process messages, other
unrelated consumers might see delays before they are delivered
JMS messages by the bus.

The delays are seen even though the asynchronous consumer
thread pool (described in APAR PK50005) has been configured to
a size equal to the number of consumers in the JVM.

A javacore shows a large number of threads within the
asynchronous consumer thread pool blocked inside the service
integration bus code, rather than calling the onMessage method
of application code. The stack of these threads is as follows:
com.ibm.ws.sib.comms.client.proxyqueue.impl.
    AsynchConsumerProxyQueueImpl.deliverMessages(
          AsynchConsumerProxyQueueImpl.java:730(Compiled Code))
com.ibm.ws.sib.comms.client.proxyqueue.asynch.
    AsynchConsumerThreadPool$ScheduleQueue.run
              AsynchConsumerThreadPool.java:197(Compiled Code))
com.ibm.ws.util.ThreadPool$Worker.run(
                           ThreadPool.java:1473(Compiled Code))

The problem is caused by an inefficiency in the algorithm that
dispatches a new message arriving from the bus to a thread
within the asynchronous consumer thread pool.
This inefficiency causes messages for quick consumers to be
randomly queued behind messages for slow consumers, even when
there should be sufficient threads available.

Problem conclusion

The fix for this APAR updates the algorihm that dispatches
messages to threads in the asynchronous consumer thread pool,
preventing the delays in delivery of messages in cases where
the size of the asynchronous consumer thread pool is sufficient.

In addition to applying the fix for this APAR, the asynchronous
consumer thread pool should be configured to contain a greater
number of threads than the maximum number of consumers that
might need to process messages concurrently. See APAR PK50005.

The fix for this APAR is currently targeted for inclusion in
fix pack 6.1.0.29 and 7.0.0.9.  Please refer to the Recommended
Updates page for delivery information:
http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980

Temporary fix

Comments

APAR Information

APAR number
PK96150
Reported component name
PLAT MSG COM
Reported component ID
620600101
Reported release
200
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2009-09-14
Closed date
2009-10-20
Last modified date
2009-10-20

APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name
PLAT MSG COM
Fixed component ID
620600101

Applicable component levels

R200 PSY
UP

[{"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"6.1","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
28 December 2021

Tips

PK96150: MESSAGE DELIVERY FOR JMS CONSUMERS USING READAHEAD STOPS INTERMITTENTLY.

Fixes are available

Subscribe

APAR status

Closed as program error.

Error description

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

APAR Information

APAR number

Reported component name

Reported component ID

Reported release

Status

PE

HIPER

Special Attention

Submitted date

Closed date

Last modified date

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name

Fixed component ID

Applicable component levels

R200 PSY

Document Information

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