[SPARK-11713] [PYSPARK] [STREAMING] Initial RDD updateStateByKey for PySpark

Adding ability to define an initial state RDD for use with updateStateByKey PySpark.  Added unit test and changed stateful_network_wordcount example to use initial RDD.

Author: Bryan Cutler <[email protected]>

Closes #10082 from BryanCutler/initial-rdd-updateStateByKey-SPARK-11713.

Author: BryanCutler

examples/src/main/python/streaming/stateful_network_wordcount.py

@@ -44,13 +44,16 @@
     ssc = StreamingContext(sc, 1)
     ssc.checkpoint("checkpoint")
 
+    # RDD with initial state (key, value) pairs
+    initialStateRDD = sc.parallelize([(u'hello', 1), (u'world', 1)])
+
     def updateFunc(new_values, last_sum):
         return sum(new_values) + (last_sum or 0)
 
     lines = ssc.socketTextStream(sys.argv[1], int(sys.argv[2]))
     running_counts = lines.flatMap(lambda line: line.split(" "))\
                           .map(lambda word: (word, 1))\
-                          .updateStateByKey(updateFunc)
+                          .updateStateByKey(updateFunc, initialRDD=initialStateRDD)
 
     running_counts.pprint()
 

python/pyspark/streaming/dstream.py

@@ -568,7 +568,7 @@ def invReduceFunc(t, a, b):
                                                              self._ssc._jduration(slideDuration))
         return DStream(dstream.asJavaDStream(), self._ssc, self._sc.serializer)
 
-    def updateStateByKey(self, updateFunc, numPartitions=None):
+    def updateStateByKey(self, updateFunc, numPartitions=None, initialRDD=None):
         """
         Return a new "state" DStream where the state for each key is updated by applying
         the given function on the previous state of the key and the new values of the key.
@@ -579,6 +579,9 @@ def updateStateByKey(self, updateFunc, numPartitions=None):
         if numPartitions is None:
             numPartitions = self._sc.defaultParallelism
 
+        if initialRDD and not isinstance(initialRDD, RDD):
+            initialRDD = self._sc.parallelize(initialRDD)
+
         def reduceFunc(t, a, b):
             if a is None:
                 g = b.groupByKey(numPartitions).mapValues(lambda vs: (list(vs), None))
@@ -590,7 +593,13 @@ def reduceFunc(t, a, b):
 
         jreduceFunc = TransformFunction(self._sc, reduceFunc,
                                         self._sc.serializer, self._jrdd_deserializer)
-        dstream = self._sc._jvm.PythonStateDStream(self._jdstream.dstream(), jreduceFunc)
+        if initialRDD:
+            initialRDD = initialRDD._reserialize(self._jrdd_deserializer)
+            dstream = self._sc._jvm.PythonStateDStream(self._jdstream.dstream(), jreduceFunc,
+                                                       initialRDD._jrdd)
+        else:
+            dstream = self._sc._jvm.PythonStateDStream(self._jdstream.dstream(), jreduceFunc)
+
         return DStream(dstream.asJavaDStream(), self._ssc, self._sc.serializer)
 
 

python/pyspark/streaming/tests.py

@@ -403,6 +403,26 @@ def func(dstream):
         expected = [[('k', v)] for v in expected]
         self._test_func(input, func, expected)
 
+    def test_update_state_by_key_initial_rdd(self):
+
+        def updater(vs, s):
+            if not s:
+                s = []
+            s.extend(vs)
+            return s
+
+        initial = [('k', [0, 1])]
+        initial = self.sc.parallelize(initial, 1)
+
+        input = [[('k', i)] for i in range(2, 5)]
+
+        def func(dstream):
+            return dstream.updateStateByKey(updater, initialRDD=initial)
+
+        expected = [[0, 1, 2], [0, 1, 2, 3], [0, 1, 2, 3, 4]]
+        expected = [[('k', v)] for v in expected]
+        self._test_func(input, func, expected)
+
     def test_failed_func(self):
         # Test failure in
         # TransformFunction.apply(rdd: Option[RDD[_]], time: Time)

streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala

@@ -264,17 +264,27 @@ private[python] class PythonTransformed2DStream(
  */
 private[python] class PythonStateDStream(
     parent: DStream[Array[Byte]],
-    reduceFunc: PythonTransformFunction)
+    reduceFunc: PythonTransformFunction,
+    initialRDD: Option[RDD[Array[Byte]]])
   extends PythonDStream(parent, reduceFunc) {
 
+  def this(
+    parent: DStream[Array[Byte]],
+    reduceFunc: PythonTransformFunction) = this(parent, reduceFunc, None)
+
+  def this(
+    parent: DStream[Array[Byte]],
+    reduceFunc: PythonTransformFunction,
+    initialRDD: JavaRDD[Array[Byte]]) = this(parent, reduceFunc, Some(initialRDD.rdd))
+
   super.persist(StorageLevel.MEMORY_ONLY)
   override val mustCheckpoint = true
 
   override def compute(validTime: Time): Option[RDD[Array[Byte]]] = {
     val lastState = getOrCompute(validTime - slideDuration)
     val rdd = parent.getOrCompute(validTime)
     if (rdd.isDefined) {
-      func(lastState, rdd, validTime)
+      func(lastState.orElse(initialRDD), rdd, validTime)
     } else {
       lastState
     }