[AMQ-9593] Add option to clean scheduled messages on startup

[kenliao94]

Working in progress: add an option to delete all scheduled message on startup.

[kenliao94]

Hey @mattrpav and @jbonofre I am curious on what you think about the approach here and want to clarify a few things:

1. I was debating between adding this logic to the job scheduler or the persistence layer (following the approach of deleteAllMessages). However, I noticed that SchedulerBroker doesn't expose their internal scheduler, and it has public methods that deal directly with Message (initially I thought SchedulerBroker is not "message aware" but only "job aware". So I decided to add the logic in SB. What do you think?

2. I wasn't able to find any other non-message jobs (even job in ByteSequence type is assumed to be unmarshal into Message) scheduled on "JMS" scheduler so I assume that remove all jobs are safe. However, do you know any pitfull for simply remove all jobs?

[kenliao94]

The PR is now ready for review.

[cshannon]

It might be be better to move the cleanup to the persistence layer just because that's how KahaDB handles clearing messages (as was pointed out). But I don't really care too much either way because the flag on the BrokerService is consistent with the other flag so for users it's still a consistent way to configure it. I'll let @mattrpav and @jbonofre comment to see if they have an opinion.

[kenliao94]

@cshannon yeah I was doing that as my first approach. But then I realize I need to somehow expose (by changing the visibility of the field) the name of the scheduler ("JMS") used by SchedulerBroker. I didn't like that approach because it creates some sort of coupling. So I decided to handle it where no visibility needed to change.

[cshannon]

Yeah that's fine, the most important thing is it's consistent for the config (which it is)

[cshannon]

I took a quick look and it generally seems ok but it would be good to have a unit test to verify it works. Something where scheduled messages are added, restart, and verify they are removed etc

[kenliao94]

Thanks for the feedback. I will add a unit test.

[mattrpav]

Scheduled message support is part of the JMS 3.1/2.0 spec. I'm not loving the separate config flag. We don't have a 'deleteAllDurableTopicMessagesOnStartup' flag. It is 'all' messages on startup.

I'm thinking it would be better to have a flag to have the scheduler ignore the deleteAllMessagesOnStartup.

Possible path forward:
v6.x - Scheduler ignores deleteAllMessagesOnStartup by default (to maintain existing behavior)
v7.x - Scheduler honors deleteAllMessagesOnStartup by default

Thoughts?

[kenliao94]

I see where you are coming from. Initially I would expect deleteAllMessagesOnStartup will include scheduled messages. I even opened a Jira ticket on it. https://issues.apache.org/jira/projects/AMQ/issues/AMQ-9572?filter=allissues from @jbonofre feedback we should have a separated flag for scheduled messages.

Regarding the proposal in v7.x I think if we have the consensus that deleteAllMessagesOnStartup should include scheduled messages then it makes sense to me.