Network Deployment (Distributed operating systems), v8.0 > Applications > Service integration > Bus destinations > Publish/subscribe messaging and topic spaces
The consequences of changing durable subscriptions
When an application connects to an existing durable subscription, but specifies parameters that differ from those that were used to create the existing subscription, the subscription is deleted then recreated with the new parameters. A durable subscription can be changed in this way only when it has no active consumers.
In the basic case, there is only one active consumer at any time, so the application can change the durable subscription without affecting other subscribers. However, the situation is more complicated for cloned subscriptions.
A cloned durable subscription has multiple active subscribers, which are usually clones of a particular application.
- For cloned message-driven bean (MDB) applications, the subscribers are always active on the subscription, and so the administrator must stop all instances of the MDB application before the subscription can be altered. (If the MDB application instances are recycled one at a time then each individual instance is thrown out when it tries to connect using the changed properties, because there are existing consumers.)
- For cloned EJB applications, administrators should ensure that all instances of the EJB application are stopped before the subscription can be changed, to avoid the following problem. Enterprise beans have active subscribers for a durable subscription for relatively short spaces of time. If the EJB application instances are recycled individually then there is a period in which different instances of the application have different views of the subscription configuration. This causes the subscription to be deleted and recreated which can lead to the loss of messages. Subscriptions can be deleted and recreated multiple times until the new definition is constant across all instances.
The server_name
durableSubscriptions.ser file in the WAS_HOME/temp directory is used by the messaging service to keep track of durable subscriptions for message-driven beans. If you uninstall an application that contains a message-driven bean, this file is used to unsubscribe the durable subscription. If we have to delete the WAS_HOME/temp directory or other files in it, ensure that you preserve this file.
Administer durable subscriptions
List subscriptions
Stop active subscribers for durable subscriptions
Delete durable subscriptions
List subscriptions
Stop active subscribers for durable subscriptions
Delete durable subscriptions