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https://issues.apache.org/jira/browse/MAPREDUCE-4495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13478253#comment-13478253
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Robert Joseph Evans commented on MAPREDUCE-4495:
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Alejandro,
I think there is a bit of a disconnect about the version of the design
associated with some of my questions. Sorry about that I did not specify it on
all of my questions. Most of my questions are about what will happen in the
V2/V3 time frame when child AMs will be running as separate processes in
containers that are launched directly by the WF AM not as containers that are
launched and monitored by the RM. I get that in V1 the WF AM will simply
launch other applications and interact with them through the client API. But
for V2 and V3 when an AM is launched by the WF AM and not directly by the RM
the WF AM must take over some responsibilities of the RM. I am curious how
many of those responsibilities it will take over. I am also curious about what
modifications will be required to other AMs so that they can interact with both
the WF AM and also the RM directly. AM I wrong about this? Is the design
different from how I understood it and the WF AM will not launch other AMs as
separate processes running in different containers?
> Workflow Application Master in YARN
> -----------------------------------
>
> Key: MAPREDUCE-4495
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4495
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Affects Versions: 2.0.0-alpha
> Reporter: Bo Wang
> Assignee: Bo Wang
> Attachments: MAPREDUCE-4495-v1.1.patch, MAPREDUCE-4495-v1.patch,
> MapReduceWorkflowAM.pdf, yapp_proposal.txt
>
>
> It is useful to have a workflow application master, which will be capable of
> running a DAG of jobs. The workflow client submits a DAG request to the AM
> and then the AM will manage the life cycle of this application in terms of
> requesting the needed resources from the RM, and starting, monitoring and
> retrying the application's individual tasks.
> Compared to running Oozie with the current MapReduce Application Master,
> these are some of the advantages:
> - Less number of consumed resources, since only one application master will
> be spawned for the whole workflow.
> - Reuse of resources, since the same resources can be used by multiple
> consecutive jobs in the workflow (no need to request/wait for resources for
> every individual job from the central RM).
> - More optimization opportunities in terms of collective resource requests.
> - Optimization opportunities in terms of rewriting and composing jobs in the
> workflow (e.g. pushing down Mappers).
> - This Application Master can be reused/extended by higher systems like Pig
> and hive to provide an optimized way of running their workflows.
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