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Hadoop >> mail # dev >> Force reducer to execute on a specific host


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RE: Force reducer to execute on a specific host
I would suggest using the AMRMClient/AMRMClientAsync libraries for this
kind of work. They take care of all the nuances like these.

Please also file a jira for the RM crash. That should not be happening.

Thanks!
Bikas

-----Original Message-----
From: Grandl Robert [mailto:[EMAIL PROTECTED]]
Sent: Sunday, November 24, 2013 8:02 PM
To: [EMAIL PROTECTED]; Grandl Robert
Subject: Re: Force reducer to execute on a specific host

I found the fix. I had to add also a rack local request for reducer. And
set the relaxLocality to false for both ANY and rack requests, in order to
force data locality.

robert
On Sunday, November 24, 2013 6:32 PM, Grandl Robert <[EMAIL PROTECTED]>
wrote:

Hi guys,

I am trying to run an experiment where I want the reducers to be forced
executing on a specific host. The simplest way I found it is to modify in
RMContainerAllocator such that whenever there is an
addContainerReq(ContainerRequest) for a reducer, I simply do:
addResourceRequest(req.priority, host_X_name, req.capability) and return,
instead of setting the resourceName to ResourceRequest.ANY.

Unfortunately when I pass such a ResourceRequest for reducers through a
makeRemoteRequest, the RM crashes, giving an ugly exception like:
FATAL org.apache.hadoop.yarn.server.resourcemanager.ResourceManager: Error
in handling event type NODE_UPDATE to the scheduler
java.lang.NullPointerException
    at
org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.LeafQueue
.assignContainers(LeafQueue.java:841)
    at
org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ParentQue
ue.assignContainersToChildQueues(ParentQueue.java:640)
    at
org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ParentQue
ue.assignContainers(ParentQueue.java:554)
    at
org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityS
cheduler.nodeUpdate(CapacityScheduler.java:695)
    at
org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityS
cheduler.handle(CapacityScheduler.java:739)
    at
org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityS
cheduler.handle(CapacityScheduler.java:86)
    at
org.apache.hadoop.yarn.server.resourcemanager.ResourceManager$SchedulerEve
ntDispatcher$EventProcessor.run(ResourceManager.java:549)
    at java.lang.Thread.run(Thread.java:722)

Do you have other suggestion how I can enforce reducers execution on a
certain host ? Or do you know what I am doing wrong here ?

Thanks,
robert

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