Network Deployment (Distributed operating systems), v8.0 > Administer applications and their environment > Administer Messaging resources > Manage messaging with the default messaging provider > Configure resources for the default messaging provider > Protect an MDB application from system resource problems
Example 1: Handling a planned outage of an MDB application external resource
We can configure the system so that, if there is a problem with a dependent external system resource, the enterprise application can continue. During the time that the system resource is unavailable, there must be no exceptions in the enterprise application, or messages on the exception destination that must be resolved later. Add a maintenance level to an external system resource used by the deployed message-driven bean (MDB) of one of the enterprise applications. The act of applying the maintenance level requires the system resource (for example, a database) to be unavailable for about five minutes.
Procedure
- Navigate to the deployed enterprise application that contains the MDB.
- From the MDB, navigate to its JMS activation specification. Click Resources -> JMS -> Activation specifications -> activation_specification_name and click Pause on the administrative panel for the MDB.
- When you receive a JMX notification and a log entry indicating that the MDB is paused, stop the database and apply the maintenance level. While the MDB is paused, no messages are sent to the exception destination and no error messages appear in the console related to the stopped database.
- Restart the database and test that it is working as expected.
- Log on to the admin console again, navigate to the same enterprise application and click Resume on the administrative panel for the MDB. We can also resume the MDB by using scripting and the JCA MBean. The initial JMX notification and log entry indicate which MBean to use to resume the MDB.
Consider registering a message listener on the JCA MBean to receive the JMX notifications. The MDB begins to be driven with the messages that are on the destination.
Results
You have paused and resumed an application while an external resource that it uses is not available for a short time.