This is a first-hand experience report for an undocumented bug found in bea Weblogic 6.1 SP3, along with a workaround for the bug
Lets clear up some vocabulary.
There are two ways the word "server" can be interpreted here. It can be taken to mean "The squarish box that is plugged into the wall and hums and clicks from time to
time" or it can mean "an instance of Weblogic". One physical "server" (the metal kind) can run
any number of weblogic server (the software kind) instances, since Weblogic is just a piece of
So to avoid this confusion I will use the word "host" when referring to a humming metal box, and the
word "instance" when referring to Weblogic.
Additionally, there may be some confusion relating to names. Each host has a name (probably charmingly
named after reindeer, or dwarves or something of the like). As well, each instance of
Weblogic has it's own name. For my purposes, I will be referring to instance names
only. Host names have no bearing on this bug.
You may now continue.
This bug manifests itself in two ways.
Manifestation #1: Connection problems.
Two instances of Weblogic (instance A, instance B) are running. They can
run either on separate hosts, or on the same host. Instance A has a JMS topic that is properly created,
and bound to the JNDI tree. Instance B has a Message Driven Beans which attempts to connect to the
JMS topic on instance A in order to receive it's messages. The MDB is correctly written, compiled and
has well-formed and proper deployment descriptors.
When deploying the MDB, instance B throws ConnectionException and\or JMSException errors. The
error messages state that the MDB was unable to connect to the remote host, and\or that the JMS topic
could not be found.
This will probably inspire you to many hours of in-depth digging around in JNDI space, instance logs
and so forth, verifying that the instance can in fact be reached, and the JMS topic is in fact
Manifestation #2: No Messages.
Three instances of Weblogic (instance A, instance B, instance C) are running. They can run either
on separate hosts, or on the same host. Instance A has a JMS topic that is properly created, and bound to
the JNDI tree. Instances B and C both have an MDB that is designed to connect to instance A's JMS topic
in order to receive it's messages. The MDBs are correctly written, compiled and have well-formed and proper
The MDB's on instances B and C are able to connect to the topic on instance A. However, only one
of the two is able to receive the messages from the topic. The other mysteriously receives no messages.
This problem is likely due to the naming of the Weblogic instances. Each Weblogic instance runs in a
domain, and has a name. For the sake of simplifying configuration management, it is common to have
multiple instances running with the same name.
Manifestation #1 occurs when instance A and instance B have the same name. If you change the name of
either instance, it should work fine.
Manifestation #2 occurs when instances B and C share a name. If you change the name of either
instance, you should begin seeing the messages arriving in both locations.
This workaround makes things rather difficult. Since it requires a unique name for each Weblogic
instance, it also requires a separate config.xml file for each instance. This makes it impossible to have
guaranteed identical configurations across instances through the use of the same config file.
Imagine a situation where an organization has three tiers of
applications (development, test, production) with two hosts in each tier and five
instances on each host. Not an unheard-of level of complexity for an enterprise. In fact, not even a
very high level of complexity for an enterprise, but this requires the management of 30
config files, when only three are actually needed (one configuration per tier). I won't even go into the
frustration of ensuring each config file for each tier is identical in every way, except for the references
to it's instance name (which are numerous).
The real cause (probably):
I'm no super-hacker, but you don't have to be a wizard of reverse engineering to see that Weblogic seems to identify incoming t3
connections by the name of the connecting instance. This may sound safe, but think about it. Would it
really have been that much more difficult to use the port number in addition to the instance name? Since
every instance requires its own port, that would uniquely identify each incoming connection.
Unless Weblogic 7 addresses this issue, or there's a forthcoming service pack 4, looks like we're just
hopelessly stuck neck-deep in config.xml files.
Hope this helps someone. Or at least entertained someone with