Example 1: Handling a planned outage of an MDB or SCA application external resource
We can configure the system so that, if there is a problem with a dependent external system resource, the enterprise or business-level application can continue.
During the time that the system resource is unavailable, there must be no exceptions in the enterprise or business-level 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 or business-level applications. The act of applying the maintenance level requires the system resource (for example, a database) to be unavailable for about five minutes.
The JCA MBean emits JMX notifications to indicate that the MDB or SCA composite is paused, and that the MDB or SCA composite has resumed. Consider registering a message listener on the JCA MBean to receive the JMX notifications.
- Navigate to the deployed enterprise application containing the MDB, or the business-level application containing the SCA composite.
- From the MDB or SCA composite, navigate to its JMS activation specification. Click Resources -> JMS -> Activation specifications -> activation_specification_name and click Pause on the administrative panel for the MDB or SCA composite.
- When you receive a JMX notification and a log entry indicating that the MDB or SCA composite is paused, stop the database and apply the maintenance level. While the MDB or SCA composite 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 console again, navigate to the same enterprise or business-level application and click Resume on the administrative panel for the MDB or SCA composite. We can also resume the MDB or SCA composite by and the JCA MBean. The initial JMX notification and log entry indicate which MBean to use to resume the MDB or SCA composite. The MDB or SCA composite 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.