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https://issues.apache.org/jira/browse/YARN-624?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13658637#comment-13658637
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Alejandro Abdelnur commented on YARN-624:
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As pointed out, supporting gang at RM/scheduler level will allow
detection/avoidance of deadlocks. This would not be trivial (nor efficient) to
do if gang is done at AM level.
Examples of gang request capabilities could be:
* express a set of containers in any nodes. I.e.: 10 containers in any node of
the cluster.
* express a set of containers in a specified set of nodes. I.e.: 10 containers
in rack1. 10 containers one in each of n1...n10
* express different sets of possible gangs that would satisfy the request:
I.e.: 10 containers in rack1 or in rack2. 10 containers in n1...n10 or in
n11..n20.
* indicate a timeout/fallback-to-normal of gang requests.
We should decide on what gang capabilities we want/need to address in the short
term.
> Support gang scheduling in the AM RM protocol
> ---------------------------------------------
>
> Key: YARN-624
> URL: https://issues.apache.org/jira/browse/YARN-624
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: api, scheduler
> Affects Versions: 2.0.4-alpha
> Reporter: Sandy Ryza
> Assignee: Sandy Ryza
>
> Per discussion on YARN-392 and elsewhere, gang scheduling, in which a
> scheduler runs a set of tasks when they can all be run at the same time,
> would be a useful feature for YARN schedulers to support.
> Currently, AMs can approximate this by holding on to containers until they
> get all the ones they need. However, this lends itself to deadlocks when
> different AMs are waiting on the same containers.
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