PQ51255: SESSION AFFINITY MADE MORE ROBUST WHEN CLONES UNAVAILABLE


APAR

APAR status
Closed as program error.

Error description
Basically, a JVM crash or system  failure  will make the
requests in certain cases to be routed to another JVM.
The plugin was already handling these failures by
attempting to reroute these requests to other clones
based on a hashing algorithm which would result in
the same clone for different requests. However, if these
retry attempts(3 of them) failed to find a clone which could
serve the request , the WLM algorithm kicked in which would
randomly select a clone.
This could lead to request being
served by multiple jvms concurrently.
Local fix
Problem summary
****************************************************************
* USERS AFFECTED: All WebSphere Application Server users       *
*                 of Session Affinity.                         *
****************************************************************
* PROBLEM DESCRIPTION: In failover situations selection of     *
*                      clones when using session affinity      *
*                      is sometimes performed via the round-   *
*                      robin.  This causes problems because    *
*                      the same clone is not guaranteed to     *
*                      be selected for subsequent requests     *
*                      with the same session id.  This only    *
*                      occurs in failover situations (when     *
*                      the clone that the session has          *
*                      affinity to is unavailable).            *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
In failover situations selection of clones when using session
affinity is sometimes performed via the round-robin.  This
causes problems because the same clone is not guaranteed to be
selected for subsequent requests with the same session id.
This only occurs in failover situations (when the clone that
the session has affinity to is unavailable).
Problem conclusion
Modified the clones selection algorithm so that in failover
situations clones will chosen in a predefined order.
Temporary fix
session.zip
Comments
APAR information
APAR numberPQ51255
Reported component nameWAS ADVANCED AI
Reported component ID5648C8400
Reported release350
StatusCLOSED PER
PENoPE
HIPERNoHIPER
Submitted date2001-08-07
Closed date2001-10-30
Last modified date2001-10-30

APAR is sysrouted FROM one or more of the following:

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


Modules/Macros
PLUGIN
APAR is sysrouted TO one or more of the following:Modules/Macros

Fix information
Fixed component nameWAS ADVANCED AI
Fixed component ID5648C8400

Applicable component levels
R350 PSYUP











Document Information

Product categories: Software, Application Servers, Distributed Application & Web Servers, WebSphere Application Server, General
Software version: 350
Reference #: PQ51255
IBM Group: Software Group
Modified date: 2001-10-30