[wsrp-interop] Java dynamic domain name workaround

[David Ward <david.ward@oracle.com>]

Title:

I just wanted to make sure I hadn't left this as a "loose end". Apologies
if you have already gathered together this information...

Richard Jacob wrote:
> Btw. could you report today about that problem and your circumvention, so
> we can pass it to the primer editor's?
The problem was that our Java mid tier, which is in our 'DMZ' (Demilitarized
Zone?) and doesn't use a proxy, was simply unable to contact the IBM service,
even though our test environment which ran through a proxy worked fine.

This turned out to be due to the way Java caches IP addresses. The java.net.InetAddress class by default caches IP addresses forever once it has resolved them once. However, the IBM domain name wsrp.dyndns.org actually gets associated with a new IP address every 24 hours, so this was bound to cause problems for our servlet container JVM that stays up forever.

If we were running on JDK 1.4, it appears we would be able to control the "time to live" for cached IP addresses through a security policy. However, it seems that the 'private' sun.net.inetaddr.ttl System property mentioned in the JDK 1.4 docs also has the same effect on JDK 1.3.

My solution was to edit the config file containing the startup options for the servlet container JVM (in Oracle 9iAS this is in opmn/conf/opmn.xml) so that the sun.net.inetaddr.ttl property is set with a small timeout (I used 120 seconds).

E.g.

java -Dsun.net.inetaddr.ttl=120 <normal JVM startup options>

Regards

David

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David Ward
Principal Software Engineer
Oracle Portal

Oracle European Development Centre
520 Oracle Parkway
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UK

Email:	david.ward@oracle.com
Tel:	+44 118 924 5079
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