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https://issues.apache.org/jira/browse/SPARK-17372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15469072#comment-15469072
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Apache Spark commented on SPARK-17372:
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User 'tdas' has created a pull request for this issue:
https://github.com/apache/spark/pull/14987
> Running a file stream on a directory with partitioned subdirs throw
> NotSerializableException/StackOverflowError
> ---------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-17372
> URL: https://issues.apache.org/jira/browse/SPARK-17372
> Project: Spark
> Issue Type: Sub-task
> Components: SQL, Streaming
> Affects Versions: 2.0.0
> Reporter: Tathagata Das
> Assignee: Tathagata Das
>
> Here is the result of my investigation. When we create a filestream on a
> directory that has partitioned subdirs (i.e. dir/x=y/), then
> ListingFileCatalog.allFiles returns the files in the dir as Seq[String] which
> internally is a Stream[String]. This is because of this
> [line|https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningAwareFileCatalog.scala#L93],
> where a LinkedHashSet.values.toSeq returns Stream. Then when the
> [FileStreamSource|https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala#L79]
> filters this Stream[String] to remove the seen files, it creates a new
> Stream[String], which has a filter function that has a $outer reference to
> the FileStreamSource (in Scala 2.10). Trying to serialize this Stream[String]
> causes NotSerializableException. This will happened even if there is just one
> file in the dir.
> Its important to note that this behavior is different in Scala 2.11. There is
> no $outer reference to FileStreamSource, so it does not throw
> NotSerializableException. However, with a large sequence of files (tested
> with 5000 files), it throws StackOverflowError. This is because how Stream
> class is implemented. Its basically like a linked list, and attempting to
> serialize a long Stream requires *recursively* going through linked list,
> thus resulting in StackOverflowError.
> The right solution is to convert the seq to an array before writing to the
> log.
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