PK74905: ALGORITHM FOR DISTRIBUTION OF MESSAGES TO CONSUMERS WITH SELECTORS UNEVENLY DISTRIBUTES MESSAGES

Fixes are available

APAR status

Closed as program error.

Error description

In a system with an MDB application deployed to a cluster of
multiple application servers (in a separate cluster to the
messaging engine) a factor of 10 difference in the number of
messages delivered to the most active consumer and the least
active consumer can be observed.
This only occurs when selectors are used in the activation
specification.

Local fix

A test fix will is supplied to make the algorithm less sensitive
to the number of messages sent by an individual producer. While
this may not make the balance of load identical between the
servers, it should improve evenness.

Problem summary

****************************************************************
* USERS AFFECTED:  Users of the default messaging provider for *
*                  WebSphere Application Server V6.1 and V7.0  *
****************************************************************
* PROBLEM DESCRIPTION: When multiple consumers consume from a  *
*                      single queue point in a bus using       *
*                      selectors, the distribution of          *
*                      messages between those consumers is     *
*                      uneven.                                 *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
When a message is sent to a queue point by a producer,
there may be multiple consumers with a selection criteria
that matches the message, and are ready to accept it.

The algorithm used by the messaging engine to choose between
consumers with selectors, is sensitive to the number of
messages that had been sent by the individual producer that
sent the message.

This resulted in uneven distribution of messages in cases
where producers only sent small numbers of messages before
disconnecting from the bus.

Problem conclusion

This APAR improves evenness of distribution between consumers
on a single queue point when selectors are used, and
each producing application sends a small number of messages
(less than 5) before disconnecting from the bus.

Some variation between the number of messages delivered to
each consumer is expected.

The fix for this APAR is currently targeted for inclusion in
fixpack 6.1.0.23 and 7.0.0.3.
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
PK74905
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
2008-11-03
Closed date
2008-11-27
Last modified date
2009-02-20

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:
29 December 2021

Tips

PK74905: ALGORITHM FOR DISTRIBUTION OF MESSAGES TO CONSUMERS WITH SELECTORS UNEVENLY DISTRIBUTES MESSAGES

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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