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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