Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/2538#discussion_r18235197
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
---
@@ -0,0 +1,275 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.streaming.api.python
+
+import java.util.{ArrayList => JArrayList, List => JList}
+import scala.collection.JavaConversions._
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+
+import org.apache.spark.api.java._
+import org.apache.spark.api.python._
+import org.apache.spark.rdd.RDD
+import org.apache.spark.storage.StorageLevel
+import org.apache.spark.streaming.{Interval, Duration, Time}
+import org.apache.spark.streaming.dstream._
+import org.apache.spark.streaming.api.java._
+
+
+/**
+ * Interface for Python callback function with three arguments
+ */
+private[python] trait PythonRDDFunction {
+ // callback in Python
+ def call(time: Long, rdds: JList[_]): JavaRDD[Array[Byte]]
+}
+
+/**
+ * Wrapper for PythonRDDFunction
+ */
+private[python] class RDDFunction(pfunc: PythonRDDFunction)
+ extends function.Function2[JList[JavaRDD[_]], Time,
JavaRDD[Array[Byte]]] with Serializable {
+
+ def apply(rdd: Option[RDD[_]], time: Time): Option[RDD[Array[Byte]]] = {
+ PythonDStream.some(pfunc.call(time.milliseconds,
List(PythonDStream.wrapRDD(rdd)).asJava))
+ }
+
+ def apply(rdd: Option[RDD[_]], rdd2: Option[RDD[_]], time: Time):
Option[RDD[Array[Byte]]] = {
+ val rdds = List(PythonDStream.wrapRDD(rdd),
PythonDStream.wrapRDD(rdd2)).asJava
+ PythonDStream.some(pfunc.call(time.milliseconds, rdds))
+ }
+
+ // for function.Function2
+ def call(rdds: JList[JavaRDD[_]], time: Time): JavaRDD[Array[Byte]] = {
+ pfunc.call(time.milliseconds, rdds)
+ }
+}
+
+
+/**
+ * Base class for PythonDStream with some common methods
+ */
+private[python]
+abstract class PythonDStream(parent: DStream[_], pfunc: PythonRDDFunction)
+ extends DStream[Array[Byte]] (parent.ssc) {
+
+ val func = new RDDFunction(pfunc)
+
+ override def dependencies = List(parent)
+
+ override def slideDuration: Duration = parent.slideDuration
+
+ val asJavaDStream = JavaDStream.fromDStream(this)
+}
+
+/**
+ * Helper functions
+ */
+private[python] object PythonDStream {
+
+ // convert Option[RDD[_]] to JavaRDD, handle null gracefully
+ def wrapRDD(rdd: Option[RDD[_]]): JavaRDD[_] = {
--- End diff --
Isnt this just `rdd.map(JavaRDD.fromRDD).orNull` ? Why not use this
directly? Sorry should have observed that earlier :)
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