When using the message broker, it is important to know who the existing subscribers in an MB cluster are, and from which nodes subscribers are consuming messages from the cluster. This can be done via the Management Console. Queue subscriptions and topic subscriptions can be viewed independently.
Whenever a queue subscription is made on the cluster, the subscription page is updated. Subscription entries will exist as long as subscriber connections are live.
The table below describes the available information:
|Exchange||The exchange to which subscription is made. For queues, this is amq.direct.|
|Queue Name||Name of the queue subscription.|
|Destination||The JMS destination that the queue represents.|
|Durability||Determines whether or not the queue is durable.|
|Active||The state of the subscriber. If a connection to the server exists, it is active.|
|Owned Node||The node from which subscription is made to the cluster. The IP address of the node is displayed.|
In addition, the number of messages tentatively pending for a subscriber are shown. While the subscriber is receiving messages, you can click Refresh to see the message count eventually decrease down to zero.
Topic subscriptions display similar information to queues. Some notable points are:
- Topic subscriptions display a queue name with subscription information. This is the internal queue name where messages belonging to the subscriber are accumulated.
- There are temporary topic subscriptions and durable topic subscriptions. Temporary topic subscriptions vanish as soon as the connection from the subscriber is closed, but durable topic subscribers are not removed from the broker. They will exist inside the broker cluster in the inActive mode.
- The message count is not displayed for temporary topic subscriptions, whereas it is displayed for durable topic subscribers.
- As inactive durable topic subscribers belong to the broker cluster, the Owned Node field is no longer applicable. If you make a subscription to the topic using the same subscription ID, that subscriber will be active once again.
- If you have the necessary permissions, you can unsubscribe the inactive durable topic subscribers. All messages belonging to that subscriber are then removed from the broker cluster. You cannot unsubscribe active durable topic subscriptions using the management console.