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From "Omkar Vinit Joshi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-613) Create NM proxy per NM instead of per container
Date Wed, 15 May 2013 18:03:18 GMT

    [ https://issues.apache.org/jira/browse/YARN-613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13658604#comment-13658604
] 

Omkar Vinit Joshi commented on YARN-613:
----------------------------------------

This was discussed offline with [~vinodkv], [~bikassaha] and [~sseth].

There were 2 viable solutions to the problem of sending AMNMToken to AM for authenticating
with NM.

Below problems need to be addressed
* The token will be generated by RM but how long the AMNMToken should be kept alive? How long
AM should be able to talk to NM on which it ever launched any container during application
life cycle.
* If the token doesn't have an expiry time then who will renew the token ? NM or RM ?.
* If NM reboots then can the old AMNMToken be reused? ( ideally when NM goes down right now
containers are also lost, so there is nothing specific to that application there in NM after
reboot)
* AM might handover the AMNMToken to some other external service ( other than AM ...may be
another container) which should be able to communicate with NM. (problem:- how if implemented
renewal will take place?)
* We need to support for long running services.
* When key roles over there should be no spiker in communicating renewed tokens if implemented.

Proposed solutions :-
* No AMNMToken renewal
** here RM will generate the token and will handover to AM only if the AM is getting the container
on underlying NM for the first time otherwise it will not send. AM can use this token to talk
to NM as long application is alive. So this is upper limited by number of applications in
the cluster <= number of nodes * number of containers per node. 
*** RM will have to remember tokens given to AM per NM
*** NM will have to remember tokens per AM
*** AM will have to anyways remember token per NM
**** Problems : If NM reboots then the token is no longer valid in which case RM should reissue
AM a new token for restarted NM
**** Advantages :
***** for every container RM doesn't have to generate and send token.
***** no need to renew the token. No added overhead. No need to remember past keys (other
than current and previous master key).
***** even if AM hands over token to some other service, that service can keep using the same
token.
* AMNMToken renewal
** here RM will generate and issue the token to AM during start container. RM also remembers
which AM has what all tokens. So when key rolls over then RM will redistribute renewed tokens
to AM for all NM on which it ever started container. AM if receives the updated token will
have to replace older with new token.
*** RM will have to remember all the NMs fro which AM handed over token
*** NM doesn't have to remember tokens per application. It only has to remember current and
previous key.
*** AM will receive AMNMToken per container request / or all tokens during key renewal. It
will have to refresh internal tokens with it
**** Advantages:
***** NM doesn't need to remember the token so there will be no problem across NM reboot.
(even though token will be valid across NM reboot but still there will be nothing on NM for
AM before new container starts).
**** Problems:
***** RM has to either remember or regenerate and send tokens to AM for container start call.
This can be avoided by just sending it when key rolls over.
***** AM has to refresh the tokens may be given to some another service for monitoring container
progress.
***** There will be spike at key role over.

                
> Create NM proxy per NM instead of per container
> -----------------------------------------------
>
>                 Key: YARN-613
>                 URL: https://issues.apache.org/jira/browse/YARN-613
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Bikas Saha
>            Assignee: Omkar Vinit Joshi
>
> Currently a new NM proxy has to be created per container since the secure authentication
is using a containertoken from the container.

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