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From "Junping Du (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-914) Support graceful decommission of nodemanager
Date Tue, 10 Feb 2015 18:52:16 GMT

    [ https://issues.apache.org/jira/browse/YARN-914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14314653#comment-14314653

Junping Du commented on YARN-914:

Thanks [~vinodkv] for comments!
bq. IAC, I think we should also have a CLI command to decommission the node which optionally
waits till the decommission succeeds.
That sounds pretty good. This new CLI can simply "gracefully" decommission related nodes and
wait to timeout to forcefully decommission nodes haven't finished. Comparing with approach
of external script proposed by Ming above, this has less dependency on effort that outside
of hadoop.  

bq. Regarding storage of the decommission state, YARN-2567 also plans to make sure that the
state of all nodes is maintained up to date on the state-store. That helps with many other
cases too. We should combine these efforts.
That make sense. However, YARN-2567 is about threshold thing, may be a wrong JIRA number?

bq. Regarding long running services, I think it makes sense to let the admin initiating the
decommission know - not in terms of policy but as a diagnostic. Other than waiting for a timeout,
the admin may not have noticed that a service is running on this node before the decommission
is triggered.

bq. This is the umbrella concern I have. There are two ways to do this: Let YARN manage the
decommission process or manage it on top of YARN. If the later is the approach, I don't see
a lot to be done here besides YARN-291. No?
Agree that there is less effort for 2nd approach. If so, we still need RM can aware containers/apps
get finished then trigger shutdown to NM to make decommission comes earlier (and randomly)
which I guess is important to upgrade of large cluster. Isn't it? For YARN-291, my understanding
is now we don't rely on any open issues left there because we only need to set NM's resource
to 0 at runtime which we already provide there. BTW, I think the approach you just proposed
above is "2nd approach + a new CLI". Isn't it? I prefer to go with this way but would like
to hear other guys' ideas here also.

> Support graceful decommission of nodemanager
> --------------------------------------------
>                 Key: YARN-914
>                 URL: https://issues.apache.org/jira/browse/YARN-914
>             Project: Hadoop YARN
>          Issue Type: Improvement
>    Affects Versions: 2.0.4-alpha
>            Reporter: Luke Lu
>            Assignee: Junping Du
>         Attachments: Gracefully Decommission of NodeManager (v1).pdf
> When NMs are decommissioned for non-fault reasons (capacity change etc.), it's desirable
to minimize the impact to running applications.
> Currently if a NM is decommissioned, all running containers on the NM need to be rescheduled
on other NMs. Further more, for finished map tasks, if their map output are not fetched by
the reducers of the job, these map tasks will need to be rerun as well.
> We propose to introduce a mechanism to optionally gracefully decommission a node manager.

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