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https://issues.apache.org/jira/browse/BEAM-8539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16965022#comment-16965022
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Luke Cwik commented on BEAM-8539:
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Another thing is whether all state transitions are required, for example if one
is in STOPPED and goes to RUNNING do they need to emit the intermediate state
STARTING.
What happens when someone wants to add a job state. For example, imagine update
was a new concept and wanted to add a new state called UPDATING which would go
from RUNNING -> UPDATING -> RUNNING, would this be a backwards incompatible
change since we are adding a job state that never existed?
> Clearly define the valid job state transitions
> ----------------------------------------------
>
> Key: BEAM-8539
> URL: https://issues.apache.org/jira/browse/BEAM-8539
> Project: Beam
> Issue Type: Improvement
> Components: beam-model, runner-core, sdk-java-core, sdk-py-core
> Reporter: Chad Dombrova
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> The Beam job state transitions are ill-defined, which is big problem for
> anything that relies on the values coming from JobAPI.GetStateStream.
> I was hoping to find something like a state transition diagram in the docs so
> that I could determine the start state, the terminal states, and the valid
> transitions, but I could not find this. The code reveals that the SDKs differ
> on the fundamentals:
> Java InMemoryJobService:
> * start state: *STOPPED*
> * run - about to submit to executor: STARTING
> * run - actually running on executor: RUNNING
> * terminal states: DONE, FAILED, CANCELLED, DRAINED
> Python AbstractJobServiceServicer / LocalJobServicer:
> * start state: STARTING
> * terminal states: DONE, FAILED, CANCELLED, *STOPPED*
> I think it would be good to make python work like Java, so that there is a
> difference in state between a job that has been prepared and one that has
> additionally been run.
> It's hard to tell how far this problem has spread within the various runners.
> I think a simple thing that can be done to help standardize behavior is to
> implement the terminal states as an enum in the beam_job_api.proto, or create
> a utility function in each language for checking if a state is terminal, so
> that it's not left up to each runner to reimplement this logic.
>
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