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It is important to note here that the messages are not dispatched to subscriber clients from the MB according to the rate at which the messages are consumed by the subscriber. For example, consider that MB dispatches 1000 messages per second to each subscriber: Subscriber A may be consuming messages at the rate of 500 messages per second, whereas subscriber B will consume all 1000 messages per second. In this scenario, 500 messages that are not acknowledged by subscriber A will always be accumulating in MB memory. If the number of unacknowledged messages increases beyond a certain point, the MB server could run out of memory. Therefore, when you work with topics, you can change the message delivery strategy according to address this issuethe requirement.
Changing the default message delivery strategy
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