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https://issues.apache.org/jira/browse/YARN-1197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13769701#comment-13769701
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Bikas Saha commented on YARN-1197:
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I am not quite sure what Exception you mention above. Reservation is the
mechanism used by the scheduler to accumulate resources on a machine till a
container request can be satisfied. If a different machine becomes free in the
meanwhile then the container should be allocated to that machine and the
reservation removed from the current machine.
Hence, if we try to allocate more resources to an acquired container, then it
will essentially go through the above cycle again. Thus we should have simply
requested the larger container in the first place.
In your use case, if you know you want a container of size X then you should
ask for X. If you dont know exactly what size you want then you can ask for a
larger container than needed. Later, while running the container if you realize
that the container can be smaller than you can reduce the size of the
container. If you realize that the container needs to be even larger then you
can increase the size of the container. It will be much easier to reduce the
size of a running container than increase the size since we are giving up
resources to the RM and that is a straightforward operation. Increasing
resource is harder because we have to wait for resources to free up. In both
cases, we will need to improve RM-AM-NM communication to inform all parties
that the container resources have changed.
I am changing the title of this jira to dynamically change the resources of an
allocated container since the same changes are needed to decrease and increase.
Decrease is simpler than increase.
> Support increasing resources of an allocated container
> ------------------------------------------------------
>
> Key: YARN-1197
> URL: https://issues.apache.org/jira/browse/YARN-1197
> Project: Hadoop YARN
> Issue Type: Task
> Components: api, nodemanager, resourcemanager
> Affects Versions: 2.1.0-beta
> Reporter: Wangda Tan
>
> Currently, YARN cannot support merge several containers in one node to a big
> container, which can make us incrementally ask resources, merge them to a
> bigger one, and launch our processes. The user scenario is described in the
> comments.
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