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From Harsh J <ha...@cloudera.com>
Subject Re: hadoop imbalanced topology
Date Mon, 28 Jan 2013 16:16:13 GMT
Hi Jameson,

Inline reply below for a specific point of yours ("scheduler deadlock"):

On Mon, Jan 28, 2013 at 8:59 PM, Jameson Li <hovlj.ei@gmail.com> wrote:
> Hi,
> Is it right that hadoop Network Topology design treat an imbalanced topology
> as an invalid topology?
> This is mentioned here
> https://issues.apache.org/jira/browse/MAPREDUCE-4095(TestJobInProgress#testLocality
> uses a bogus topology.)
> said:"(https://issues.apache.org/jira/secure/attachment/12345251/Rack_aware_HDFS_proposal.pdf)
> which does not support imbalanced topology. "
> But when I re-read the desigh pdf, there just draw a balanced topology but
> really not mentioned it will not support imbalanced topology.
> Also I found this JIRA:
> https://issues.apache.org/jira/browse/HADOOP-8159(NetworkTopology: getLeaf
> should check for invalid topologies).
> Just no why for my question, because of the design(Right?):
> Why below is a invalid topology(except imbalanced), for hadoop rack
> awareness:
> serverA /default-rack    ##default rack
> serverB /dc1/rack2    ##actually the node has a pre "dc1"
> Should all of the hadoop datanode have the same level number? If not, there
> will be some issues for namenode and jt(like scheduler deadlock)?

This was a problem in earlier releases, where an imbalanced or
improper config for topology levels could lead to a jarring halt in
the JobTracker's schedulers. This has been fixed in 1.1.0 already via

Harsh J

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