[SPARK-11870][STREAMING][PYSPARK] Rethrow the exceptions in TransformFunction...

[SPARK-11870][STREAMING][PYSPARK] Rethrow the exceptions in TransformFunction and TransformFunctionSerializer

TransformFunction and TransformFunctionSerializer don't rethrow the exception, so when any exception happens, it just return None. This will cause some weird NPE and confuse people.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #9847 from zsxwing/pyspark-streaming-exception.

python/pyspark/streaming/tests.py

@@ -403,6 +403,22 @@ class BasicOperationTests(PySparkStreamingTestCase):
         expected = [[('k', v)] for v in expected]
         self._test_func(input, func, expected)
 
+    def test_failed_func(self):
+        input = [self.sc.parallelize([d], 1) for d in range(4)]
+        input_stream = self.ssc.queueStream(input)
+
+        def failed_func(i):
+            raise ValueError("failed")
+
+        input_stream.map(failed_func).pprint()
+        self.ssc.start()
+        try:
+            self.ssc.awaitTerminationOrTimeout(10)
+        except:
+            return
+
+        self.fail("a failed func should throw an error")
+
 
 class StreamingListenerTests(PySparkStreamingTestCase):
 

python/pyspark/streaming/util.py

@@ -64,6 +64,7 @@ class TransformFunction(object):
                 return r._jrdd
         except Exception:
             traceback.print_exc()
+            raise
 
     def __repr__(self):
         return "TransformFunction(%s)" % self.func
@@ -95,6 +96,7 @@ class TransformFunctionSerializer(object):
             return bytearray(self.serializer.dumps((func.func, func.deserializers)))
         except Exception:
             traceback.print_exc()
+            raise
 
     def loads(self, data):
         try:
@@ -102,6 +104,7 @@ class TransformFunctionSerializer(object):
             return TransformFunction(self.ctx, f, *deserializers)
         except Exception:
             traceback.print_exc()
+            raise
 
     def __repr__(self):
         return "TransformFunctionSerializer(%s)" % self.serializer