GitHub user aarondav opened a pull request:
https://github.com/apache/spark/pull/1503
SPARK-2282: Reuse Socket for sending accumulator updates to Pyspark
Prior to this change, every PySpark task completion opened a new socket to
the accumulator server, passed its updates through, and then quit. I'm not
entirely sure why PySpark always sends accumulator updates, but regardless this
causes a very rapid buildup of ephemeral TCP connections that remain in the
TCP_WAIT state for around a minute before being cleaned up.
Rather than trying to allow these sockets to be cleaned up faster, this
patch simply reuses the connection between tasks completions (since they're fed
updates in a single-threaded manner by the DAGScheduler anyway).
The only tricky part here was making sure that the AccumulatorServer was
able to shutdown in a timely manner (i.e., stop polling for new data), and this
was accomplished via minor feats of magic.
I have confirmed that this patch eliminates the buildup of ephemeral
sockets due to the accumulator updates. However, I did note that there were
still significant sockets being created against the PySpark daemon port, but my
machine was not able to create enough sockets fast enough to fail. This may not
be the last time we've seen this issue, though.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/aarondav/spark accum
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/1503.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1503
----
commit b3e12f7504150b8f355e263d740d8f4c2f788820
Author: Aaron Davidson <[email protected]>
Date: 2014-07-20T23:31:18Z
SPARK-2282: Reuse Socket for sending accumulator updates to Pyspark
Prior to this change, every PySpark task completion opened a new
socket to the accumulator server, passed its updates through, and
then quit. I'm not entirely sure why PySpark always sends accumulator
updates, but regardless this causes a very rapid buildup of ephemeral
TCP connections that remain in the TCP_WAIT state for around a minute
before being cleaned up.
Rather than trying to allow these sockets to be cleaned up faster, this
patch simply reuses the connection between tasks completions (since they're
fed updates in a single-threaded manner by the DAGScheduler anyway).
The only tricky part here was making sure that the AccumulatorServer was
able to shutdown in a timely manner (i.e., stop polling for new data), and
this was accomplished via minor feats of magic.
----
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