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https://issues.apache.org/jira/browse/FLINK-18625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17160862#comment-17160862
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Xintong Song commented on FLINK-18625:
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Thanks for the clarification, [~Jiangang].
Configuring absolute number of task managers makes sense to me.
Would you like to prepare a PR for this ticket?
> Maintain redundant taskmanagers to speed up failover
> ----------------------------------------------------
>
> Key: FLINK-18625
> URL: https://issues.apache.org/jira/browse/FLINK-18625
> Project: Flink
> Issue Type: New Feature
> Components: Runtime / Coordination
> Reporter: Liu
> Priority: Major
>
> When flink job fails because of killed taskmanagers, it will request new
> containers when restarting. Requesting new containers can be very slow,
> sometimes it takes dozens of seconds even more. The reasons can be different,
> for example, yarn and hdfs are slow, machine performance is poor. In some
> product scenario, SLA is high and failover should be in seconds.
>
> To speed up the recovery process, we can maintain redundant taskmanagers in
> advance. When job restarts, it can use the redundant taskmanagers at once
> instead of requesting new taskmanagers.
>
> The implemention can be done in SlotManagerImpl. Below is a brief description:
> # In construct method, init redundantTaskmanagerNum from config.
> # In method start(), allocate redundant taskmanagers.
> # In method start(), Change taskManagerTimeoutCheck() to
> redundantTaskmanagerCheck().
> # In method redundantTaskmanagerCheck(), manage redundant taskmanagers and
> timeout taskmanagers. The idle taskmanager number must be not less than
> redundantTaskmanagerNum.
> * If less, allocate from resourceManager until equal.
> * If more, release timeout taskmanagers but keep at least
> redundantTaskmanagerNum idle taskmanagers.
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