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Date: Mon, 11 Mar 2013 23:21:14 +0000 (UTC)
From: "Roger Hoover (JIRA)" <jira@apache.org>
To: yarn-dev@hadoop.apache.org
Message-ID: <JIRA.12636468.1363044038962.422002.1363044074028@arcas>
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Subject: [jira] [Created] (YARN-466) Slave hostname mismatches in
 ResourceManager/Scheduler
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Roger Hoover created YARN-466:
---------------------------------

             Summary: Slave hostname mismatches in ResourceManager/Scheduler
                 Key: YARN-466
                 URL: https://issues.apache.org/jira/browse/YARN-466
             Project: Hadoop YARN
          Issue Type: Bug
          Components: resourcemanager, scheduler
            Reporter: Roger Hoover


The problem is that the ResourceManager learns the hostname of a slave node when the NodeManager registers itself and it seems the node manager is getting the hostname by asking the OS.  When a job is submitted, I think the ApplicationMaster learns the hostname by doing a reverse DNS lookup based on the slaves file.

Therefore, the ApplicationMaster submits requests for containers using the fully qualified domain name (node1.foo.com) but the scheduler uses the OS hostname (node1) when checking to see if any requests are node-local.  The result is that node-local requests are never found using this method of searching for node-local requests:

ResourceRequest request = application.getResourceRequest(priority, node.getHostName());

I think it's unfriendly to ask users to make sure they configure hostnames to match fully qualified domain names. There should be a way for the ApplicationMaster and NodeManager to agree on the hostname.

Steps to Reproduce:
1) Configure the OS hostname on slaves to differ from the fully qualified domain name.  For example, if the FQDN for the slave is "node1.foo.com", set the hostname on the node to be just "node1".
2) On submitting a job, observe that the AM submits resource requests using the FQDN (e.g. "node1.foo.com").  You can add logging to the allocate() method of whatever scheduler you're using 

for (ResourceRequest req: ask) {
      LOG.debug(String.format("Request %s for %d containers on %s", req, req.getNumContainers(), req.getHostName()));
    }
3) Observe that when the scheduler checks for node locality (in the handle() method) using the FiCaSchedulerNode.getHostName(), the hostname is uses is the one set in the host OS (e.g. "node1").  NOTE: if you're using FifoScheduler, this bug needs to be fixed first (https://issues.apache.org/jira/browse/YARN-412).  


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