[jira] [Created] (FLINK-33092) Improve the resource-stabilization-timeout mechanism when rescale a job for Adaptive Scheduler

["Rui Fan (Jira)" <ji...@apache.org>]

Rui Fan created FLINK-33092:
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             Summary: Improve the resource-stabilization-timeout mechanism when rescale a job for Adaptive Scheduler
                 Key: FLINK-33092
                 URL: https://issues.apache.org/jira/browse/FLINK-33092
             Project: Flink
          Issue Type: Improvement
          Components: Runtime / Coordination
            Reporter: Rui Fan
            Assignee: Rui Fan
         Attachments: image-2023-09-15-14-43-35-104.png

!image-2023-09-15-14-43-35-104.png|width=776,height=548!
h1. 1. Propose

The above is the state transition graph when rescale a job in Adaptive Scheduler.

In brief, when we trigger a rescale, the job will wait _*resource-stabilization-timeout*_ in WaitingForResources State when it has sufficient resources and it doesn't have the desired resource.

If the _*resource-stabilization-timeout mechanism*_ is moved into the Executing State, the rescale downtime will be significantly reduced.
h1. 2. Why the downtime is long?can be significantly reduced

Currently, when rescale a job:
 * The Executing will transition to Restarting
 * The Restarting will cancel this job first.
 * The Restarting will transition to WaitingForResources after the whole job is terminal.
 * When this job has sufficient resources and it doesn't have the desired resource, the WaitingForResources needs to wait  _*resource-stabilization-timeout*_ .
 * WaitingForResources will transition to CreatingExecutionGraph after  resource-stabilization-timeout.

The problem is the job isn't running during the resource-stabilization-timeout phase.
h1. 3. How to reduce the downtime?

We can move the _*resource-stabilization-timeout mechanism*_ into the Executing State when trigger a rescale. It means:
 * When this job has desired resources, the Executing can rescale directly.
 * When this job has sufficient resources and it doesn't have the desired resource, we can rescale after _*resource-stabilization-timeout.*_
 * The WaitingForResources will ignore the resource-stabilization-timeout after this improvement.

The resource-stabilization-timeout works before cancel job, so the rescale downtime will be significantly reduced.

 

Note: the resource-stabilization-timeout still works in WaitingForResources when start a job. It's just changed when rescale a job.



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