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https://issues.apache.org/jira/browse/HDFS-6166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13951493#comment-13951493
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Nathan Roberts commented on HDFS-6166:
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Maybe our two comments passed in the mail. Yes I tested internally. It's been
running on a 400 node cluster for 1 day. I ran with bandwidths of 500K, 6MB,
20MB. With 500K there were timeouts, but no thread quota exceeded failures.
> revisit balancer so_timeout
> ----------------------------
>
> Key: HDFS-6166
> URL: https://issues.apache.org/jira/browse/HDFS-6166
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: balancer
> Affects Versions: 3.0.0, 2.3.0
> Reporter: Nathan Roberts
> Assignee: Nathan Roberts
> Priority: Blocker
> Attachments: HDFS-6166.patch
>
>
> HDFS-5806 changed the socket read timeout for the balancer connection to DN
> to 60 seconds. This works as long as balancer bandwidth is such that it's
> safe to assume that the DN will easily complete the operation within this
> time. Obviously this isn't a good assumption. When this assumption isn't
> valid, the balancer will timeout the cmd BUT it will then be out-of-sync with
> the datanode (balancer thinks the DN has room to do more work, DN is still
> working on the request and will fail any subsequent requests with "threads
> quota exceeded errors"). This causes expensive NN traffic via getBlocks() and
> also causes lots of WARNS int the balancer log.
> Unfortunately the protocol is such that it's impossible to tell if the DN is
> busy working on replacing the block, OR is in bad shape and will never finish.
> So, in the interest of a small change to deal with both situations, I propose
> the following two changes:
> * Crank of the socket read timeout to 20 minutes
> * Delay looking at a node for a bit if we did timeout in this way (the DN
> could still have xceiver threads working on the replace
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