GitHub user dhruve opened a pull request:
https://github.com/apache/spark/pull/18487
[SPARK-21243][Core] Limit no. of map outputs in a shuffle fetch
## What changes were proposed in this pull request?
For configurations with external shuffle enabled, we have observed that if
a very large no. of blocks are being fetched from a remote host, it puts the NM
under extra pressure and can crash it. This change introduces a configuration
`spark.reducer.maxBlocksInFlightPerAddress` , to limit the no. of map outputs
being fetched from a given remote address. The changes applied here are
applicable for both the scenarios - when external shuffle is enabled as well as
disabled.
## How was this patch tested?
Ran the job with the default configuration which does not change the
existing behavior and ran it with few configurations of lower values
-10,20,50,100. The job ran fine and there is no change in the output. (I will
update the metrics related to NM in some time.)
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dhruve/spark impr/SPARK-21243
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18487.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 #18487
----
commit d60a0bef35e1c38108d3b18a40b7dc01ed8b814f
Author: Dhruve Ashar <[email protected]>
Date: 2017-06-30T12:58:35Z
[SPARK-21243][Core] Limit no. of map outputs in a shuffle fetch
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