Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/7710#discussion_r35609409
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/ScriptTransformation.scala
---
@@ -146,49 +198,83 @@ case class ScriptTransformation(
}
}
- val (inputSerde, inputSoi) = ioschema.initInputSerDe(input)
- val dataOutputStream = new DataOutputStream(outputStream)
- val outputProjection = new InterpretedProjection(input, child.output)
+ writerThread.start()
- // TODO make the 2048 configurable?
- val stderrBuffer = new CircularBuffer(2048)
- // Consume the error stream from the pipeline, otherwise it will be
blocked if
- // the pipeline is full.
- new RedirectThread(errorStream, // input stream from the pipeline
- stderrBuffer, // output to a circular buffer
- "Thread-ScriptTransformation-STDERR-Consumer").start()
+ outputIterator
+ }
- // Put the write(output to the pipeline) into a single thread
- // and keep the collector as remain in the main thread.
- // otherwise it will causes deadlock if the data size greater than
- // the pipeline / buffer capacity.
- new Thread(new Runnable() {
- override def run(): Unit = {
- Utils.tryWithSafeFinally {
- iter
- .map(outputProjection)
- .foreach { row =>
- if (inputSerde == null) {
- val data = row.mkString("",
ioschema.inputRowFormatMap("TOK_TABLEROWFORMATFIELD"),
-
ioschema.inputRowFormatMap("TOK_TABLEROWFORMATLINES")).getBytes("utf-8")
-
- outputStream.write(data)
- } else {
- val writable = inputSerde.serialize(
- row.asInstanceOf[GenericInternalRow].values, inputSoi)
- prepareWritable(writable).write(dataOutputStream)
- }
- }
- outputStream.close()
- } {
- if (proc.waitFor() != 0) {
- logError(stderrBuffer.toString) // log the stderr circular
buffer
- }
- }
- }
- }, "Thread-ScriptTransformation-Feed").start()
+ child.execute().mapPartitions { iter =>
+ if (iter.hasNext) {
+ processIterator(iter)
+ } else {
+ // If the input iterator has no rows then do not launch the
external script.
+ Iterator.empty
+ }
+ }
+ }
+}
- iterator
+private class ScriptTransformationWriterThread(
+ iter: Iterator[InternalRow],
+ outputProjection: Projection,
+ @Nullable inputSerde: AbstractSerDe,
+ @Nullable inputSoi: ObjectInspector,
+ ioschema: HiveScriptIOSchema,
+ outputStream: OutputStream,
+ proc: Process,
+ stderrBuffer: CircularBuffer,
+ taskContext: TaskContext
+ ) extends Thread("Thread-ScriptTransformation-Feed") with Logging {
+
+ setDaemon(true)
+
+ @volatile private var _exception: Throwable = null
+
+ /** Contains the exception thrown while writing the parent iterator to
the external process. */
+ def exception: Option[Throwable] = Option(_exception)
--- End diff --
This error-handling technique is based off similar code in PythonRDD: the
writer thread exposes a method for checking whether an exception occurred and
the reader thread checks for exceptions in order to distinguish between EOFs
due to errors and EOFs due to reaching the end of the input. See
https://github.com/apache/spark/blob/daa1964b6098f79100def78451bda181b5c92198/core/src/main/scala/org/apache/spark/api/python/PythonRDD.scala#L195
for the PySpark code.
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