Wangda Tan commented on YARN-1197:

Thanks for interesting in this ticket, some comments:
bq. For JVM based containers (e.g., container running HBase), it is not 
possible right now to change the heap size of JVM without restarting the Java 
process. Even if we can implement a wrapper in the container to relaunch a Java 
process when resource is changed for a container, we still need to implement an 
interface between node manager and container to trigger the relaunch action.
Good point, this is one thing we noted as well. I don't think there's any easy 
solution to shrink JVM. Relaunch the container could be one method, but it will 
be hard to make a generic "container wrapper" since kill and relaunch will make 
data in memory lost.

But since the shrink memory is a proactive action, when a process wants to 
shrink its resource, it can use its own "container wrapper" to relaunch the 
process if it has some data recovery mechanism.

> Support changing 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
>         Attachments: mapreduce-project.patch.ver.1, 
> tools-project.patch.ver.1, yarn-1197-scheduler-v1.pdf, yarn-1197-v2.pdf, 
> yarn-1197-v3.pdf, yarn-1197-v4.pdf, yarn-1197-v5.pdf, yarn-1197.pdf, 
> yarn-api-protocol.patch.ver.1, yarn-pb-impl.patch.ver.1, 
> yarn-server-common.patch.ver.1, yarn-server-nodemanager.patch.ver.1, 
> yarn-server-resourcemanager.patch.ver.1
> The current YARN resource management logic assumes resource allocated to a 
> container is fixed during the lifetime of it. When users want to change a 
> resource 
> of an allocated container the only way is releasing it and allocating a new 
> container with expected size.
> Allowing run-time changing resources of an allocated container will give us 
> better control of resource usage in application side

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