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From raghavendhra rahul <raghavendhrara...@gmail.com>
Subject Re: Yarn related questions:
Date Thu, 05 Jan 2012 04:04:59 GMT

I tried to set the client node for launching the container within the
application master.
I have set the parameter as
but the containers are not launched in the destined host.Instead the loop
goes on continuously.
2012-01-04 15:11:48,535 INFO appmaster.ApplicationMaster
(ApplicationMaster.java:run(204)) - Current application state: loop=95,
appDone=false, total=2, requested=2, completed=0, failed=0,

On Wed, Jan 4, 2012 at 11:24 PM, Robert Evans <evans@yahoo-inc.com> wrote:

>  Ann,
> A container more or less corresponds to a task in MRV1.  There is one
> exception to this, as the ApplicationMaster also runs in a container.  The
> ApplicationMaster will request new containers for each mapper or reducer
> task that it wants to launch.  There is separate code from the container
> that will serve up the intermediate mapper output and is run as part of the
> NodeManager (Similar to the TaskTracker from before).  When the
> ApplicationMaster requests a container it also includes with it a hint as
> to where it would like the container placed.  In fact it actually makes
> three request one for the exact node, one for the rack the node is on, and
> one that is generic and could be anywhere.  The scheduler will try to honor
> those requests in the same order so data locality is still considered and
> generally honored.  Yes there is the possibility of back and forth to get a
> container, but the ApplicationMaster generally will try to use all of the
> containers that it is given, even if they are not optimal.
> --Bobby Evans
> On 1/4/12 10:23 AM, "Ann Pal" <ann_r_pal@yahoo.com> wrote:
> Hi,
> I am trying to understand more about Hadoop Next Gen Map Reduce and had
> the following questions based on the following post:
> http://developer.yahoo.com/blogs/hadoop/posts/2011/03/mapreduce-nextgen-scheduler/
> [1] How does application decide how many containers it needs? The
> containers are used to store the intermediate result at the map nodes?
> [2] During resource allocation, if the resource manager has no mapping
> between map tasks to resources allocated, how can it properly allocate the
> right resources. It might end up allocating resources on a node, which does
> not have data for the map task, and hence is not optimal. In this case the
> Application Master will have to reject it and request again . There could
> be considerable back- and- forth between application master and resource
> manager before it could converge. Is this right?
> Thanks!

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