PM03894: ADD AN OPTION TO DISABLE THE HOSTNAME NORMALIZER CACHING.

Fixes are available

APAR status

Closed as new function.

Error description

The WebSphere JNDI / CosNaming implementation normalizes
hostnames so that various forms of a hostname are all
converted into a single normalized form.  This normalization
ensures that the same JNDI cache is used regardless of how the
bootstrap host is specified in the provider URL.  For
performance reasons, normalization results are cached by using
the default hostname normalizer. This caching interferes with
DNS implementations which return different results from one
call to the next.

Local fix

WebSphere JNDI / CosNaming exposes hostname normalization in
the form of a public interface which customers can implement.
The implementation of choice is specified through a published
property setting
(com.ibm.websphere.naming.hostname.normalizer). The default
setting is WebSphere's hostname normalizer implementation. The
customer could implement their own hostname normalizer that
does not cache the normalization results and set the property
to use their normalizer.

Problem summary

****************************************************************
* USERS AFFECTED:  All users of IBM WebSphere Application      *
*                  Server V7.0                                 *
****************************************************************
* PROBLEM DESCRIPTION: Stale address from the JNDI cache is    *
*                      used as the bootstrap host in the       *
*                      provider URL when the DNS lookup        *
*                      results changes dynamically.            *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
The WebSphere JNDI / CosNaming implementation of
DefaultHostnameNormalizer normalizes hostnames so that various
forms of a hostname are all converted into a single normalized
form.  This normalization ensures that the same JNDI cache is
used regardless of how the bootstrap host is specified in the
provider URL.  For performance reasons, normalization results
are cached by using the default hostname normalizer. This
caching interferes with DNS implementations which return
different results from one call to the next. An example of
such DNS implementations is the DNS round-robin for workload
distribution across a set of machines.

Problem conclusion

To disable the hostname normalization and hence its caching,
specify a new property value for the hostname normalizer
property as the following:

Import java.util.Hashtable;
import com.ibm.websphere.naming.PROPS;
[...]
Hashtable env = new Hashtable();
env.put(PROPS.HOSTNAME_NORMALIZER,
PROPS.HOSTNAME_NORMALIZER_NONE);
Context ic = new InitialContext(env);
[...]

Alternatively, the hostname normalizer property can be set as
a system property or in a jndi.properties file as
"com.ibm.websphere.naming.hostname.normalizer=...none..." to
disable the hostname normalization.

The fix for this APAR is currently targeted for inclusion in
fix pack 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

WebSphere JNDI / CosNaming exposes hostname normalization in
the form of a public interface which customers can implement.
The implementation of choice is specified through a published
property setting,
"com.ibm.websphere.naming.hostname.normalizer". A non-caching
hostname normalizer implementation can be used to workaround
this issue.

Comments

APAR Information

APAR number
PM03894
Reported component name
WEBS APP SERV N
Reported component ID
5724H8800
Reported release
700
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2009-12-17
Closed date
2010-01-06
Last modified date
2010-01-06

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
WEBS APP SERV N
Fixed component ID
5724H8800

Applicable component levels

R700 PSY
UP

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"7.0","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
24 October 2021

Tips

PM03894: ADD AN OPTION TO DISABLE THE HOSTNAME NORMALIZER CACHING.

Fixes are available

Subscribe

APAR status

Closed as new function.

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

R700 PSY

Document Information

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