Github user jaceklaskowski commented on a diff in the pull request:
https://github.com/apache/spark/pull/14292#discussion_r71870635
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/HDFSMetadataLog.scala
---
@@ -91,18 +92,30 @@ class HDFSMetadataLog[T: ClassTag](sparkSession:
SparkSession, path: String)
serializer.deserialize[T](ByteBuffer.wrap(bytes))
}
+ /**
+ * Store the metadata for the specified batchId and return `true` if
successful. If the batchId's
+ * metadata has already been stored, this method will return `false`.
+ *
+ * Note that this method must be called on a
[[org.apache.spark.util.UninterruptibleThread]]
+ * so that interrupts can be disabled while writing the batch file. This
is because there is a
+ * potential dead-lock in Hadoop "Shell.runCommand" before 2.5.0
(HADOOP-10622). If the thread
+ * running "Shell.runCommand" is interrupted, then the thread can get
deadlocked. In our
+ * case, `writeBatch` creates a file using HDFS API and calls
"Shell.runCommand" to set the
+ * file permissions, and can get deadlocked is the stream execution
thread is stopped by
+ * interrupt. Hence, we make sure that this method is called on
UninterruptibleThread which
--- End diff --
`[[org.apache.spark.util.UninterruptibleThread]]` (as you do below)
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