Details
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Improvement
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Status: Open
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Major
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Resolution: Unresolved
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Description
I've mostly worked on flink 1.9-1.12, but I believe this is still an issue today.
I've worked on a few flink applications now that have struggled to reliably activate new versions of a currently running job. Sometimes, users make changes to a job graph that make it so state cannot be restored. Sometimes users make changes to a job graph that make it unable to be scheduled on a given cluster (increased parallelism with insufficient task slots on the cluster). These validations are performed here
It's not flink's problem that these issues arise, but these issues are only detected when the JM tries to run the given jobgraph. For exactly once applications (and other applications where running two job graphs for the same application is undesirable) there is unneeded downtime when users submit jobgraphs with breaking changes because users must cancel the old job, submit the new job to see if it is valid and will activate, and then resubmit the old job when activation fails. As a user with low-latency requirements, this change management solution is unfortunate, and there doesn't seem to be anything technical preventing these validations from happening earlier.
Suggestion: provide a mechanism for users to (1) create and (2) validate the new job graph+checkpoint without running it so that they do not need to cancel a currently running version of the job until they're more sure it will activate