MQSeries.net :: View topic

mpuetz · Posted: Sat Mar 16, 2002 2:22 pm Post subject:

Hi,

after some interesting deployment nightmares (brokers
crashing randomly leaving execution groups in an inconsistent
state, even after restarting the broker) with my
custom plugin nodes I eventually found out, that the
context and all attributes must be freed manually in the
deleteNodeContext() function. I found this out only after
analyzing some of the sources of other plugins which do
this explicitly. What was totally confusing to me was
the following fact: The programming guide states you should
use the deleteContextNode() function to free plugin resources
created in the createNodeContext() function, hence I assumed
I should free the context myself. However looking at the
samples provided with MQSI (BipSampPluginNode.c) the default
context (which is provided by the plugin node wizard) is *not*
freed nor any mamory for the node attributes.
Also the wizard generated template doesn't free the context.
Therefore I was completely mislead into the assumption that freeing
the context and its attributes was taken
care of in the framework and only freeing additional resources
allocated in createNodeContext() was my responsibilty.

Apparently, the developer creating the BisSampPluginNode fell into
the same pit as I did, trusting the wizard to generate well formed
code which does nothing, but works *reliably*.
Thus, any MQSI developer monitoring this: Please, get the examples
and the wizard templates fixed ! Examples with mistakes like this
are not helpful, but are very confusing and cost a lot of time
(and money) to find out ! Especially since these mistakes don't show
up in the way that one anticipates.
Mow, after this little rant, I actually have a real question about the
plugin interface.

I can use detachElement() to remove a subtree from a message, but
there is actually no deleteElement() call in the interface. So, what
happens if I don't attach the element again at some other place ?
When will the memory of detached elements be freed (will it be freed
at all) ?

_________________
Mathias Puetz

IBM/Central WebSphere Services
WebSphere Business Integration Specialist