From d29e2ef4cf43c7f7c5aa40d305cf02be44ce19e0 Mon Sep 17 00:00:00 2001
From: Shixiong Zhu <shixiong@databricks.com>
Date: Wed, 25 Nov 2015 11:47:21 -0800
Subject: [SPARK-11935][PYSPARK] Send the Python exceptions in
 TransformFunction and TransformFunctionSerializer to Java

The Python exception track in TransformFunction and TransformFunctionSerializer is not sent back to Java. Py4j just throws a very general exception, which is hard to debug.

This PRs adds `getFailure` method to get the failure message in Java side.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #9922 from zsxwing/SPARK-11935.
---
 .../spark/streaming/api/python/PythonDStream.scala | 52 ++++++++++++++++++----
 1 file changed, 43 insertions(+), 9 deletions(-)

(limited to 'streaming/src/main')

diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
index dfc569451d..994309ddd0 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
@@ -26,6 +26,7 @@ import scala.language.existentials
 
 import py4j.GatewayServer
 
+import org.apache.spark.SparkException
 import org.apache.spark.api.java._
 import org.apache.spark.rdd.RDD
 import org.apache.spark.storage.StorageLevel
@@ -40,6 +41,13 @@ import org.apache.spark.util.Utils
  */
 private[python] trait PythonTransformFunction {
   def call(time: Long, rdds: JList[_]): JavaRDD[Array[Byte]]
+
+  /**
+   * Get the failure, if any, in the last call to `call`.
+   *
+   * @return the failure message if there was a failure, or `null` if there was no failure.
+   */
+  def getLastFailure: String
 }
 
 /**
@@ -48,6 +56,13 @@ private[python] trait PythonTransformFunction {
 private[python] trait PythonTransformFunctionSerializer {
   def dumps(id: String): Array[Byte]
   def loads(bytes: Array[Byte]): PythonTransformFunction
+
+  /**
+   * Get the failure, if any, in the last call to `dumps` or `loads`.
+   *
+   * @return the failure message if there was a failure, or `null` if there was no failure.
+   */
+  def getLastFailure: String
 }
 
 /**
@@ -59,18 +74,27 @@ private[python] class TransformFunction(@transient var pfunc: PythonTransformFun
   extends function.Function2[JList[JavaRDD[_]], Time, JavaRDD[Array[Byte]]] {
 
   def apply(rdd: Option[RDD[_]], time: Time): Option[RDD[Array[Byte]]] = {
-    Option(pfunc.call(time.milliseconds, List(rdd.map(JavaRDD.fromRDD(_)).orNull).asJava))
-      .map(_.rdd)
+    val rdds = List(rdd.map(JavaRDD.fromRDD(_)).orNull).asJava
+    Option(callPythonTransformFunction(time.milliseconds, rdds)).map(_.rdd)
   }
 
   def apply(rdd: Option[RDD[_]], rdd2: Option[RDD[_]], time: Time): Option[RDD[Array[Byte]]] = {
     val rdds = List(rdd.map(JavaRDD.fromRDD(_)).orNull, rdd2.map(JavaRDD.fromRDD(_)).orNull).asJava
-    Option(pfunc.call(time.milliseconds, rdds)).map(_.rdd)
+    Option(callPythonTransformFunction(time.milliseconds, rdds)).map(_.rdd)
   }
 
   // for function.Function2
   def call(rdds: JList[JavaRDD[_]], time: Time): JavaRDD[Array[Byte]] = {
-    pfunc.call(time.milliseconds, rdds)
+    callPythonTransformFunction(time.milliseconds, rdds)
+  }
+
+  private def callPythonTransformFunction(time: Long, rdds: JList[_]): JavaRDD[Array[Byte]] = {
+    val resultRDD = pfunc.call(time, rdds)
+    val failure = pfunc.getLastFailure
+    if (failure != null) {
+      throw new SparkException("An exception was raised by Python:\n" + failure)
+    }
+    resultRDD
   }
 
   private def writeObject(out: ObjectOutputStream): Unit = Utils.tryOrIOException {
@@ -103,23 +127,33 @@ private[python] object PythonTransformFunctionSerializer {
   /*
    * Register a serializer from Python, should be called during initialization
    */
-  def register(ser: PythonTransformFunctionSerializer): Unit = {
+  def register(ser: PythonTransformFunctionSerializer): Unit = synchronized {
     serializer = ser
   }
 
-  def serialize(func: PythonTransformFunction): Array[Byte] = {
+  def serialize(func: PythonTransformFunction): Array[Byte] = synchronized {
     require(serializer != null, "Serializer has not been registered!")
     // get the id of PythonTransformFunction in py4j
     val h = Proxy.getInvocationHandler(func.asInstanceOf[Proxy])
     val f = h.getClass().getDeclaredField("id")
     f.setAccessible(true)
     val id = f.get(h).asInstanceOf[String]
-    serializer.dumps(id)
+    val results = serializer.dumps(id)
+    val failure = serializer.getLastFailure
+    if (failure != null) {
+      throw new SparkException("An exception was raised by Python:\n" + failure)
+    }
+    results
   }
 
-  def deserialize(bytes: Array[Byte]): PythonTransformFunction = {
+  def deserialize(bytes: Array[Byte]): PythonTransformFunction = synchronized {
     require(serializer != null, "Serializer has not been registered!")
-    serializer.loads(bytes)
+    val pfunc = serializer.loads(bytes)
+    val failure = serializer.getLastFailure
+    if (failure != null) {
+      throw new SparkException("An exception was raised by Python:\n" + failure)
+    }
+    pfunc
   }
 }
 
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