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https://issues.apache.org/jira/browse/SPARK-6962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14499308#comment-14499308
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Aaron Davidson commented on SPARK-6962:
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Executor logs in particular. Are all remaining tasks hanging and on all
different machines? Similar to what Patrick said, if there's an asymmetry on
the machines it could suggest one has stopped responding and everyone is
waiting on it. It's possible that only one Executor is behaving in an erratic
way, though it's abnormal too that the connection didn't just timeout after
some time and the task be retried.
> Netty BlockTransferService hangs in the middle of SQL query
> -----------------------------------------------------------
>
> Key: SPARK-6962
> URL: https://issues.apache.org/jira/browse/SPARK-6962
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.2.0, 1.2.1, 1.3.0
> Reporter: Jon Chase
> Attachments: jstacks.txt
>
>
> Spark SQL queries (though this seems to be a Spark Core issue - I'm just
> using queries in the REPL to surface this, so I mention Spark SQL) hang
> indefinitely under certain (not totally understood) circumstances.
> This is resolved by setting spark.shuffle.blockTransferService=nio, which
> seems to point to netty as the issue. Netty was set as the default for the
> block transport layer in 1.2.0, which is when this issue started. Setting
> the service to nio allows queries to complete normally.
> I do not see this problem when running queries over smaller (~20 5MB files)
> datasets. When I increase the scope to include more data (several hundred
> ~5MB files), the queries will get through several steps but eventuall hang
> indefinitely.
> Here's the email chain regarding this issue, including stack traces:
> http://mail-archives.apache.org/mod_mbox/spark-user/201503.mbox/<cae61spfqt2y7d5vqzomzz2dmr-jx2c2zggcyky40npkjjx4...@mail.gmail.com>
> For context, here's the announcement regarding the block transfer service
> change:
> http://mail-archives.apache.org/mod_mbox/spark-dev/201411.mbox/<cabpqxssl04q+rbltp-d8w+z3atn+g-um6gmdgdnh-hzcvd-...@mail.gmail.com>
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