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https://issues.apache.org/jira/browse/MAPREDUCE-3251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13152473#comment-13152473
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Anupam Seth commented on MAPREDUCE-3251:
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bq. Unless I'm missing something here, a client not only talk with MR side,
often it does HDFS operations; and for this it needs network access to all
cluster nodes. Unless you force them to use something like Hoop. Also, in MR2
land, where are splits being calculated?, this requires HDFS access.
I probably do not just have any depth of understanding here, but will access to
HDFS not be an issue for the client in the kind of scenario this is attempting
to address since what is blocking is the port ACL not being opened up?
> Network ACLs can prevent some clients to talk to MR ApplicationMaster
> ---------------------------------------------------------------------
>
> Key: MAPREDUCE-3251
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3251
> Project: Hadoop Map/Reduce
> Issue Type: Task
> Components: mrv2
> Affects Versions: 0.23.0
> Reporter: Anupam Seth
> Assignee: Anupam Seth
> Priority: Critical
> Fix For: 0.23.1
>
> Attachments: MAPREDUCE-3251_branch-0_23_preliminary.txt
>
>
> In 0.20.xxx, the JobClient while polling goes to JT to get the job status.
> With YARN, AM can be launched on any port and the client will have to have
> ACL open to that port to talk to AM and get the job status. When the client
> is within the same grid network access to AM is not a problem. But some
> applications may have one installation per set of clusters and may launch
> jobs even across such sets (on job trackers in another set of clusters). For
> that to work only the JT port needs to be open currently. In case of YARN,
> all ports will have to be opened up for things to work. That would be a
> security no-no.
> There are two possible solutions:
> 1) Make the job client only talk to RM (as an option) to get the job
> status.
> 2) Limit the range of ports AM can listen on.
> Option 2) may not be favorable as there is no direct OS API to find a free
> port.
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