GitHub user JoshRosen opened a pull request:
https://github.com/apache/spark/pull/14952
[SPARK-17110] Fix StreamCorruptionException in
BlockManager.getRemoteValues()
## What changes were proposed in this pull request?
This patch fixes a `java.io.StreamCorruptedException` error affecting
remote reads of cached values when certain data types are used. The problem
stems from #11801 / SPARK-13990, a patch to have Spark automatically pick the
"best" serializer when caching RDDs. If PySpark cached a PythonRDD, then this
would be cached as an `RDD[Array[Byte]]` and the automatic serializer selection
would pick KryoSerializer for replication and block transfer. However, the
`getRemoteValues()` / `getRemoteBytes()` code path did not pass proper class
tags in order to enable the same serializer to be used during deserialization,
causing Java to be inappropriately used instead of Kryo, leading to the
StreamCorruptedException.
We already fixed a similar bug in #14311, which dealt with similar issues
in block replication. Prior to that patch, it seems that we had no tests to
ensure that block replication actually succeeded. Similarly, prior to this bug
fix patch it looks like we had no tests to perform remote reads of cached data,
which is why this bug was able to remain latent for so long.
This patch addresses the bug by modifying `BlockManager`'s `get()` and
`getRemoteValues()` methods to accept ClassTags, allowing the proper class tag
to be threaded in the `getOrElseUpdate` code path (which is used by
`rdd.iterator`)
## How was this patch tested?
Extended the caching tests in `DistributedSuite` to exercise the
`getRemoteValues` path, plus manual testing to verify that the PySpark bug
reproduction in SPARK-17110 is fixed.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/JoshRosen/spark SPARK-17110
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14952.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 #14952
----
commit 470380e48a9bf574ee6cfc2700bd044b70276cd8
Author: Josh Rosen <[email protected]>
Date: 2016-09-03T17:26:52Z
Add regression test.
commit 9eb75f57bbb7ee0c555bbdd26cf4187ee0ad3671
Author: Josh Rosen <[email protected]>
Date: 2016-09-03T17:31:43Z
Fix bug by threading proper ClassTag
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