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https://issues.apache.org/jira/browse/HDFS-4417?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Colin Patrick McCabe resolved HDFS-4417.
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Resolution: Fixed
submitted
> HDFS-347: fix case where local reads get disabled incorrectly
> -------------------------------------------------------------
>
> Key: HDFS-4417
> URL: https://issues.apache.org/jira/browse/HDFS-4417
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, hdfs-client, performance
> Reporter: Todd Lipcon
> Assignee: Colin Patrick McCabe
> Attachments: fail.patch, HDFS-4417.002.patch, HDFS-4417.003.patch,
> HDFS-4417.004.patch, hdfs-4417.txt
>
>
> In testing HDFS-347 against HBase (thanks [~jdcryans]) we ran into the
> following case:
> - a workload is running which puts a bunch of local sockets in the PeerCache
> - the workload abates for a while, causing the sockets to go "stale" (ie the
> DN side disconnects after the keepalive timeout)
> - the workload starts again
> In this case, the local socket retrieved from the cache failed the
> newBlockReader call, and it incorrectly disabled local sockets on that host.
> This is similar to an earlier bug HDFS-3376, but not quite the same.
> The next issue we ran into is that, once this happened, it never tried local
> sockets again, because the cache held lots of TCP sockets. Since we always
> managed to get a cached socket to the local node, it didn't bother trying
> local read again.
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