Resequencer should not be storing released messages. It should only remember the sequence number of the highest rated Message [INT-2135]

[spring-operator]

Oleg Zhurakousky opened INT-2135 and commented

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Affects: 2.1 M1

This issue is a sub-task of #6135

[spring-operator]

Mark Fisher commented

Even for Resequencer, only the LAST released Message needs to be remembered.

[spring-operator]

Oleg Zhurakousky commented

Right, but probably not even the message, just the sequence number. After all this is a resequencer (a very specialized use case), so storing a Message exposes us to potentially making some decisions based on the Message where we only have to make decision based on the sequence number

[spring-operator]

Gary Russell commented

I think the message retention should be delegated to the release strategy - the release strategy knows what it needs to keep around for the "next" release. Maybe some release strategy might not need all the messages, but it might need more than the last one.

Something like...

List<Message<?>> canPurge(List<Message<?> released);

OTOH, I like the idea of just keeping metadata around rather than complete messages that have already been released.

[spring-operator]

Oleg Zhurakousky commented

Part of the problem is that MARKED is a @ManagedAttribute as of now, but thinking about it even for management purposes you really interested in the counter at best, not the whole message list. If you were you could have add a wiretap with claim-check downstream and store all the released messages.

[spring-operator]

Oleg Zhurakousky commented

Also, it seems like allowing custom ReleaseStrategy on the Resequencer is wrong since internally after ReleaseStrategy had returned 'true' the there will be a call to ResequencingMessageGroupProcessor to complete the group and produce messages that needs to be released. That logic is relying on presence of the 'sequenceNumber', so if one not present (e.g., you were trying to rely on the payload values for the release - 1, 2, 3) two things will happen.

1. Messages that are currently accumulated in the UNMARKED will be released
2. They wil be released in the order in which they came in (arbitrary)

IMHO Resequencer is a very specialized use case and therefore should not be as configurable as aggregator. In other words there should not be exposing 'release-strategy*' attributes

[spring-operator]

Oleg Zhurakousky commented

Currently with modifications made, the resequencer will only store the sequence number of the last released Message. There is a new method on the MessageGroupStore.setLastReleasedSequenceNumberForGroup() and corresponding method on MessageGroup.getLastReleasedMessageSequence(). The MARKED messages is optional since it is only used for monitoring (still in question though since we may only need to store the counter of the released messages) and is controlled now by 'keep-released-messages' attribute of the Aggregator/Resequencer