apply event sourcing to message subscriptions #6920
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This commit also contains some automatic reformatting applied
- also remove sentTime information from subescription state - reduce and rename signatures of new interface
replace sentTime field in subscription state with correlating flag
- reduce visibility of methods - improve thread safety
This is a reluctant change. Initially I was hoping to find a way to update the sent time when the command is actually being sent, instead of using the time when the persistent update is made. However, updating the command sent time at the point when the command is sent is a bigger undertaking. Commands can be sent by different classes, none of which have the transient state immediately available.
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Description
This applies event sourcing to message subscriptions.
This implementation largely reflects option 2 described in the ticket.
It does so by defining an interface for the transient state. With this interface in place the following dependencies are introduced:
Pending...SubscriptionCheckernow depends on the transient state interface (and no longer on mutable persistent state interfaceThe implementation of the transient state is based on a simple sorted set.
Furthermore
sentTimefields are removed from persistent state altogether.Major Flaws
The transient state does not participate in transaction rollback. As such the transient state can get out of sync with persistent state. In such a scenario, a command could be resent ad infinitum, because it will never be removed from transient state.
Other Shortcomings
commandSentTimeis not always updated exactly when the command is sent, it is sometimes updated when the persistent state is changed (which is a good proxy, but not precise)Related issues
closes #6364
Definition of Done
Code changes:
backport stable/0.25) to the PR, in case that fails you need to create backports manually.Testing:
Documentation: