[jira] [Created] (AMQ-5361) Allow for multiple slow consumer strategies to be used together

["Tim Bain (JIRA)" <ji...@apache.org>]

Tim Bain created AMQ-5361:
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             Summary: Allow for multiple slow consumer strategies to be used together
                 Key: AMQ-5361
                 URL: https://issues.apache.org/jira/browse/AMQ-5361
             Project: ActiveMQ
          Issue Type: Improvement
          Components: Broker
    Affects Versions: 5.9.0
            Reporter: Tim Bain


AMQ-378 allowed a pluggable policy for aborting consumers that were slow, where a consumer was slow if the broker was holding a number of messages for it equal to the consumer's prefetch buffer size, in addition to the same number of messages already in the consumer's prefetch buffer.  AMQ-4621 added the ability to use a different slow consumer strategy and provided one other strategy, to consider a consumer slow if it hasn't acked a message in a certain amount of time.

These strategies each has certain things it protects well against while not protecting against others, but I want the ability to be protected from all of them, by being able to select multiple SlowConsumerStrategy implementations for my needs.  This would also allow us to use future SlowConsumerStrategy implementations alongside the two that exist today.

In the short term, this might be as simple as turning PolicyEntry.slowConsumerStrategy into a Set<SlowConsumerStrategy> and performing all actions on each entry in the set.

In the longer term, we should think about whether it would be better to break the SlowConsumerStrategy interface apart to pull out a SlowConsumerIdentificationStrategy interface that would let us pass a consumer to a method and have it tell us whether it considers the consumer to be slow (calling each of those in turn, since that's really what we'd want to have a multiplicity > 1), and a separate SlowConsumerHandlerStrategy interface that would let us choose what action to take in response when we figure out that a consumer is slow (which could probably have a multiplicity of 1).  If the implementer chooses not to do this longer-term refactoring as part of resolving this issue, then please split it out into a separate JIRA to capture it for the future.



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