There are a set of checks that you can carry out to investigate
why messages are not being consumed at a destination on a service
integration bus, when the messages are being routed through a remote
message point and the consuming application is stopped.
About this task
Complete this task as part of either
Investigating why point-to-point messages are not being consumed or
Investigating why publish/subscribe messages are not arriving at a subscription. This task
explains how to investigate the flow of messages in a scenario where
the messages are being routed through a remote message point and the
consuming application is stopped.
The following diagrams
illustrate two possible scenarios. In Figure 1, a bus contains three
messaging engines, ME1, ME2 and ME3. The producing application is
connected to ME1 and the consuming application is connected to ME3.
The messages are routed from ME1 to ME3 through ME2, and are consumed
from ME3. This scenario is only concerned with ME2 and ME3. ME3 hosts
a remote message point that represents the message point hosted by
ME2. In Figure 2, ME2 and ME3 host publication points that are represented
by remote publication points on ME1, where the producing application
is attached. Subscribing application B is connected to ME3 and receives
messages indirectly from ME1, through a subscription on ME2. a remote
subscription point on ME 3. These messaging engines are referred to
in the following steps.Figure 1. Point-to-point
message consumption by using a remote message point
Figure 2. Publish/subscribe messaging by using a remote message point 
Procedure
- If you have followed the steps in Investigating why point-to-point messages are not being consumed or Investigating why publish/subscribe messages are not arriving at a subscription before starting
this task, you should have displayed a list of message requests. On
the previous panel (runtime properties for the message point), check
that the Message requests issued (point-to-point
only) or Message requests received (publish/subscribe
only) value is greater than zero. If the value is not greater than
zero, no requests have been made. Check the consuming application
for errors:
- Check that the application is connected to ME2.
- Check that the application did not produce any errors that might
explain why messages are not being consumed.
- Check that the consumer was started.
- Check that the application did attempt to consume a message:
- If the application uses an asynchronous consumer, check that the
asynchronous consumer was registered.
- If the application is synchronous, check that the consumer performed
a "receive" or a "receive with wait" function (this might
require a modification to the application to extend the time that
the application waits for a message).
- If the number of issued message requests is greater than
zero, requests from ME3 to ME2 for messages on the message point have
been made. Check that the Completed message requests value
is greater than zero. If not, check that the two messaging engines
can communicate with each other, see Service integration troubleshooting: Checking the communication between two messaging engines in a bus.
- If the number of completed message requests is greater
than zero, requests are being issued by ME3, processed by ME2 and
completed back to ME3. To ensure that those requests were made by
the application being investigated, record the current values of Completed
message requests and either Message requests
issued or Message requests received.
Rerun the consuming application and check that both values have increased.
If the values do not increase, the application did not make a request
from ME3 to ME2 for this message point (the existing numbers relate
to a previous application that was consuming messages). Check the
consuming application for errors:
- Check that the application was started.
- Check that the name of the destination being consumed from is
correct.
- If the values do increase, the message request was issued
and completed, but no message was returned or processed by the consuming
application.
- Check that the application selection criteria match the available
message or messages on the message point.
- Check that the application is correctly receiving the message,
by checking for application or runtime errors.
What to do next
If you are still having problems, contact your IBM customer
service representative.