[SPARK-3660][STREAMING] Initial RDD for updateStateByKey transformation

SPARK-3660 : Initial RDD for updateStateByKey transformation

I have added a sample StatefulNetworkWordCountWithInitial inspired by StatefulNetworkWordCount.

Please let me know if any changes are required.

Author: Soumitra Kumar <kumar.soumitra@gmail.com>

Closes apache#2665 from soumitrak/master and squashes the following commits:

ee8980b [Soumitra Kumar] Fixed copy/paste issue.
304f636 [Soumitra Kumar] Added simpler version of updateStateByKey API with initialRDD and test.
9781135 [Soumitra Kumar] Fixed test, and renamed variable.
3da51a2 [Soumitra Kumar] Adding updateStateByKey with initialRDD API to JavaPairDStream.
2f78f7e [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
d4fdd18 [Soumitra Kumar] Renamed variable and moved method.
d0ce2cd [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
31399a4 [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
4efa58b [Soumitra Kumar] [SPARK-3660][STREAMING] Initial RDD for updateStateByKey transformation
8f40ca0 [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
dde4271 [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
fdd7db3 [Soumitra Kumar] Adding support of initial value for state update. SPARK-3660 : Initial RDD for updateStateByKey transformation

examples/src/main/scala/org/apache/spark/examples/streaming/StatefulNetworkWordCount.scala

@@ -18,12 +18,13 @@
 package org.apache.spark.examples.streaming
 
 import org.apache.spark.SparkConf
+import org.apache.spark.HashPartitioner
 import org.apache.spark.streaming._
 import org.apache.spark.streaming.StreamingContext._
 
 /**
  * Counts words cumulatively in UTF8 encoded, '\n' delimited text received from the network every
- * second.
+ * second starting with initial value of word count.
  * Usage: StatefulNetworkWordCount <hostname> <port>
  *   <hostname> and <port> describe the TCP server that Spark Streaming would connect to receive
  *   data.
@@ -51,20 +52,28 @@ object StatefulNetworkWordCount {
       Some(currentCount + previousCount)
     }
 
+    val newUpdateFunc = (iterator: Iterator[(String, Seq[Int], Option[Int])]) => {
+      iterator.flatMap(t => updateFunc(t._2, t._3).map(s => (t._1, s)))
+    }
+
     val sparkConf = new SparkConf().setAppName("StatefulNetworkWordCount")
     // Create the context with a 1 second batch size
     val ssc = new StreamingContext(sparkConf, Seconds(1))
     ssc.checkpoint(".")
 
-    // Create a ReceiverInputDStream on target ip:port and count the
+    // Initial RDD input to updateStateByKey
+    val initialRDD = ssc.sparkContext.parallelize(List(("hello", 1), ("world", 1)))
+
+    // Create a NetworkInputDStream on target ip:port and count the
     // words in input stream of \n delimited test (eg. generated by 'nc')
     val lines = ssc.socketTextStream(args(0), args(1).toInt)
     val words = lines.flatMap(_.split(" "))
     val wordDstream = words.map(x => (x, 1))
 
     // Update the cumulative count using updateStateByKey
     // This will give a Dstream made of state (which is the cumulative count of the words)
-    val stateDstream = wordDstream.updateStateByKey[Int](updateFunc)
+    val stateDstream = wordDstream.updateStateByKey[Int](newUpdateFunc,
+      new HashPartitioner (ssc.sparkContext.defaultParallelism), true, initialRDD)
     stateDstream.print()
     ssc.start()
     ssc.awaitTermination()

streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaPairDStream.scala

@@ -492,6 +492,25 @@ class JavaPairDStream[K, V](val dstream: DStream[(K, V)])(
     dstream.updateStateByKey(convertUpdateStateFunction(updateFunc), partitioner)
   }
 
+  /**
+   * 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.
+   * org.apache.spark.Partitioner is used to control the partitioning of each RDD.
+   * @param updateFunc State update function. If `this` function returns None, then
+   *                   corresponding state key-value pair will be eliminated.
+   * @param partitioner Partitioner for controlling the partitioning of each RDD in the new
+   *                    DStream.
+   * @param initialRDD initial state value of each key.
+   * @tparam S State type
+   */
+  def updateStateByKey[S](
+      updateFunc: JFunction2[JList[V], Optional[S], Optional[S]],
+      partitioner: Partitioner,
+      initialRDD: JavaPairRDD[K, S]
+  ): JavaPairDStream[K, S] = {
+    implicit val cm: ClassTag[S] = fakeClassTag
+    dstream.updateStateByKey(convertUpdateStateFunction(updateFunc), partitioner, initialRDD)
+  }
 
   /**
    * Return a new DStream by applying a map function to the value of each key-value pairs in

streaming/src/main/scala/org/apache/spark/streaming/dstream/PairDStreamFunctions.scala

@@ -410,7 +410,54 @@ class PairDStreamFunctions[K, V](self: DStream[(K,V)])
       partitioner: Partitioner,
       rememberPartitioner: Boolean
     ): DStream[(K, S)] = {
-     new StateDStream(self, ssc.sc.clean(updateFunc), partitioner, rememberPartitioner)
+     new StateDStream(self, ssc.sc.clean(updateFunc), partitioner, rememberPartitioner, 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.
+   * org.apache.spark.Partitioner is used to control the partitioning of each RDD.
+   * @param updateFunc State update function. If `this` function returns None, then
+   *                   corresponding state key-value pair will be eliminated.
+   * @param partitioner Partitioner for controlling the partitioning of each RDD in the new
+   *                    DStream.
+   * @param initialRDD initial state value of each key.
+   * @tparam S State type
+   */
+  def updateStateByKey[S: ClassTag](
+      updateFunc: (Seq[V], Option[S]) => Option[S],
+      partitioner: Partitioner,
+      initialRDD: RDD[(K, S)]
+    ): DStream[(K, S)] = {
+    val newUpdateFunc = (iterator: Iterator[(K, Seq[V], Option[S])]) => {
+      iterator.flatMap(t => updateFunc(t._2, t._3).map(s => (t._1, s)))
+    }
+    updateStateByKey(newUpdateFunc, partitioner, true, initialRDD)
+  }
+
+  /**
+   * 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 each key.
+   * org.apache.spark.Partitioner is used to control the partitioning of each RDD.
+   * @param updateFunc State update function. If `this` function returns None, then
+   *                   corresponding state key-value pair will be eliminated. Note, that
+   *                   this function may generate a different a tuple with a different key
+   *                   than the input key. It is up to the developer to decide whether to
+   *                   remember the partitioner despite the key being changed.
+   * @param partitioner Partitioner for controlling the partitioning of each RDD in the new
+   *                    DStream
+   * @param rememberPartitioner Whether to remember the paritioner object in the generated RDDs.
+   * @param initialRDD initial state value of each key.
+   * @tparam S State type
+   */
+  def updateStateByKey[S: ClassTag](
+      updateFunc: (Iterator[(K, Seq[V], Option[S])]) => Iterator[(K, S)],
+      partitioner: Partitioner,
+      rememberPartitioner: Boolean,
+      initialRDD: RDD[(K, S)]
+    ): DStream[(K, S)] = {
+     new StateDStream(self, ssc.sc.clean(updateFunc), partitioner,
+       rememberPartitioner, Some(initialRDD))
   }
 
   /**

streaming/src/main/scala/org/apache/spark/streaming/dstream/StateDStream.scala

@@ -30,7 +30,8 @@ class StateDStream[K: ClassTag, V: ClassTag, S: ClassTag](
     parent: DStream[(K, V)],
     updateFunc: (Iterator[(K, Seq[V], Option[S])]) => Iterator[(K, S)],
     partitioner: Partitioner,
-    preservePartitioning: Boolean
+    preservePartitioning: Boolean,
+    initialRDD : Option[RDD[(K, S)]]
   ) extends DStream[(K, S)](parent.ssc) {
 
   super.persist(StorageLevel.MEMORY_ONLY_SER)
@@ -41,6 +42,25 @@ class StateDStream[K: ClassTag, V: ClassTag, S: ClassTag](
 
   override val mustCheckpoint = true
 
+  private [this] def computeUsingPreviousRDD (
+    parentRDD : RDD[(K, V)], prevStateRDD : RDD[(K, S)]) = {
+    // Define the function for the mapPartition operation on cogrouped RDD;
+    // first map the cogrouped tuple to tuples of required type,
+    // and then apply the update function
+    val updateFuncLocal = updateFunc
+    val finalFunc = (iterator: Iterator[(K, (Iterable[V], Iterable[S]))]) => {
+      val i = iterator.map(t => {
+        val itr = t._2._2.iterator
+        val headOption = if(itr.hasNext) Some(itr.next) else None
+        (t._1, t._2._1.toSeq, headOption)
+      })
+      updateFuncLocal(i)
+    }
+    val cogroupedRDD = parentRDD.cogroup(prevStateRDD, partitioner)
+    val stateRDD = cogroupedRDD.mapPartitions(finalFunc, preservePartitioning)
+    Some(stateRDD)
+  }
+
   override def compute(validTime: Time): Option[RDD[(K, S)]] = {
 
     // Try to get the previous state RDD
@@ -51,25 +71,7 @@ class StateDStream[K: ClassTag, V: ClassTag, S: ClassTag](
         // Try to get the parent RDD
         parent.getOrCompute(validTime) match {
           case Some(parentRDD) => {   // If parent RDD exists, then compute as usual
-
-            // Define the function for the mapPartition operation on cogrouped RDD;
-            // first map the cogrouped tuple to tuples of required type,
-            // and then apply the update function
-            val updateFuncLocal = updateFunc
-            val finalFunc = (iterator: Iterator[(K, (Iterable[V], Iterable[S]))]) => {
-              val i = iterator.map(t => {
-                val itr = t._2._2.iterator
-                val headOption = itr.hasNext match {
-                  case true => Some(itr.next())
-                  case false => None
-                }
-                (t._1, t._2._1.toSeq, headOption)
-              })
-              updateFuncLocal(i)
-            }
-            val cogroupedRDD = parentRDD.cogroup(prevStateRDD, partitioner)
-            val stateRDD = cogroupedRDD.mapPartitions(finalFunc, preservePartitioning)
-            Some(stateRDD)
+            computeUsingPreviousRDD (parentRDD, prevStateRDD)
           }
           case None => {    // If parent RDD does not exist
 
@@ -90,19 +92,25 @@ class StateDStream[K: ClassTag, V: ClassTag, S: ClassTag](
         // Try to get the parent RDD
         parent.getOrCompute(validTime) match {
           case Some(parentRDD) => {   // If parent RDD exists, then compute as usual
+            initialRDD match {
+              case None => {
+                // Define the function for the mapPartition operation on grouped RDD;
+                // first map the grouped tuple to tuples of required type,
+                // and then apply the update function
+                val updateFuncLocal = updateFunc
+                val finalFunc = (iterator : Iterator[(K, Iterable[V])]) => {
+                  updateFuncLocal (iterator.map (tuple => (tuple._1, tuple._2.toSeq, None)))
+                }
 
-            // Define the function for the mapPartition operation on grouped RDD;
-            // first map the grouped tuple to tuples of required type,
-            // and then apply the update function
-            val updateFuncLocal = updateFunc
-            val finalFunc = (iterator: Iterator[(K, Iterable[V])]) => {
-              updateFuncLocal(iterator.map(tuple => (tuple._1, tuple._2.toSeq, None)))
+                val groupedRDD = parentRDD.groupByKey (partitioner)
+                val sessionRDD = groupedRDD.mapPartitions (finalFunc, preservePartitioning)
+                // logDebug("Generating state RDD for time " + validTime + " (first)")
+                Some (sessionRDD)
+              }
+              case Some (initialStateRDD) => {
+                computeUsingPreviousRDD(parentRDD, initialStateRDD)
+              }
             }
-
-            val groupedRDD = parentRDD.groupByKey(partitioner)
-            val sessionRDD = groupedRDD.mapPartitions(finalFunc, preservePartitioning)
-            // logDebug("Generating state RDD for time " + validTime + " (first)")
-            Some(sessionRDD)
           }
           case None => { // If parent RDD does not exist, then nothing to do!
             // logDebug("Not generating state RDD (no previous state, no parent)")

streaming/src/test/java/org/apache/spark/streaming/JavaAPISuite.java

@@ -806,15 +806,17 @@ public void testUnion() {
    * Performs an order-invariant comparison of lists representing two RDD streams. This allows
    * us to account for ordering variation within individual RDD's which occurs during windowing.
    */
-  public static <T extends Comparable<T>> void assertOrderInvariantEquals(
+  public static <T> void assertOrderInvariantEquals(
       List<List<T>> expected, List<List<T>> actual) {
+    List<Set<T>> expectedSets = new ArrayList<Set<T>>();
     for (List<T> list: expected) {
-      Collections.sort(list);
+      expectedSets.add(Collections.unmodifiableSet(new HashSet<T>(list)));
     }
+    List<Set<T>> actualSets = new ArrayList<Set<T>>();
     for (List<T> list: actual) {
-      Collections.sort(list);
+      actualSets.add(Collections.unmodifiableSet(new HashSet<T>(list)));
     }
-    Assert.assertEquals(expected, actual);
+    Assert.assertEquals(expectedSets, actualSets);
   }
 
 
@@ -1239,6 +1241,49 @@ public Optional<Integer> call(List<Integer> values, Optional<Integer> state) {
     Assert.assertEquals(expected, result);
   }
 
+  @SuppressWarnings("unchecked")
+  @Test
+  public void testUpdateStateByKeyWithInitial() {
+    List<List<Tuple2<String, Integer>>> inputData = stringIntKVStream;
+
+    List<Tuple2<String, Integer>> initial = Arrays.asList (
+            new Tuple2<String, Integer> ("california", 1),
+            new Tuple2<String, Integer> ("new york", 2));
+
+    JavaRDD<Tuple2<String, Integer>> tmpRDD = ssc.sparkContext().parallelize(initial);
+    JavaPairRDD<String, Integer> initialRDD = JavaPairRDD.fromJavaRDD (tmpRDD);
+
+    List<List<Tuple2<String, Integer>>> expected = Arrays.asList(
+        Arrays.asList(new Tuple2<String, Integer>("california", 5),
+            new Tuple2<String, Integer>("new york", 7)),
+        Arrays.asList(new Tuple2<String, Integer>("california", 15),
+            new Tuple2<String, Integer>("new york", 11)),
+        Arrays.asList(new Tuple2<String, Integer>("california", 15),
+            new Tuple2<String, Integer>("new york", 11)));
+
+    JavaDStream<Tuple2<String, Integer>> stream = JavaTestUtils.attachTestInputStream(ssc, inputData, 1);
+    JavaPairDStream<String, Integer> pairStream = JavaPairDStream.fromJavaDStream(stream);
+
+    JavaPairDStream<String, Integer> updated = pairStream.updateStateByKey(
+        new Function2<List<Integer>, Optional<Integer>, Optional<Integer>>() {
+        @Override
+        public Optional<Integer> call(List<Integer> values, Optional<Integer> state) {
+          int out = 0;
+          if (state.isPresent()) {
+            out = out + state.get();
+          }
+          for (Integer v: values) {
+            out = out + v;
+          }
+          return Optional.of(out);
+        }
+        }, new HashPartitioner(1), initialRDD);
+    JavaTestUtils.attachTestOutputStream(updated);
+    List<List<Tuple2<String, Integer>>> result = JavaTestUtils.runStreams(ssc, 3, 3);
+
+    assertOrderInvariantEquals(expected, result);
+  }
+
   @SuppressWarnings("unchecked")
   @Test
   public void testReduceByKeyAndWindowWithInverse() {

streaming/src/test/scala/org/apache/spark/streaming/BasicOperationsSuite.scala

@@ -30,6 +30,7 @@ import org.apache.spark.rdd.{BlockRDD, RDD}
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.StreamingContext._
 import org.apache.spark.streaming.dstream.{DStream, WindowedDStream}
+import org.apache.spark.HashPartitioner
 
 class BasicOperationsSuite extends TestSuiteBase {
   test("map") {
@@ -350,6 +351,79 @@ class BasicOperationsSuite extends TestSuiteBase {
     testOperation(inputData, updateStateOperation, outputData, true)
   }
 
+  test("updateStateByKey - simple with initial value RDD") {
+    val initial = Seq(("a", 1), ("c", 2))
+
+    val inputData =
+      Seq(
+        Seq("a"),
+        Seq("a", "b"),
+        Seq("a", "b", "c"),
+        Seq("a", "b"),
+        Seq("a"),
+        Seq()
+      )
+
+    val outputData =
+      Seq(
+        Seq(("a", 2), ("c", 2)),
+        Seq(("a", 3), ("b", 1), ("c", 2)),
+        Seq(("a", 4), ("b", 2), ("c", 3)),
+        Seq(("a", 5), ("b", 3), ("c", 3)),
+        Seq(("a", 6), ("b", 3), ("c", 3)),
+        Seq(("a", 6), ("b", 3), ("c", 3))
+      )
+
+    val updateStateOperation = (s: DStream[String]) => {
+      val initialRDD = s.context.sparkContext.makeRDD(initial)
+      val updateFunc = (values: Seq[Int], state: Option[Int]) => {
+        Some(values.sum + state.getOrElse(0))
+      }
+      s.map(x => (x, 1)).updateStateByKey[Int](updateFunc,
+        new HashPartitioner (numInputPartitions), initialRDD)
+    }
+
+    testOperation(inputData, updateStateOperation, outputData, true)
+  }
+
+  test("updateStateByKey - with initial value RDD") {
+    val initial = Seq(("a", 1), ("c", 2))
+
+    val inputData =
+      Seq(
+        Seq("a"),
+        Seq("a", "b"),
+        Seq("a", "b", "c"),
+        Seq("a", "b"),
+        Seq("a"),
+        Seq()
+      )
+
+    val outputData =
+      Seq(
+        Seq(("a", 2), ("c", 2)),
+        Seq(("a", 3), ("b", 1), ("c", 2)),
+        Seq(("a", 4), ("b", 2), ("c", 3)),
+        Seq(("a", 5), ("b", 3), ("c", 3)),
+        Seq(("a", 6), ("b", 3), ("c", 3)),
+        Seq(("a", 6), ("b", 3), ("c", 3))
+      )
+
+    val updateStateOperation = (s: DStream[String]) => {
+      val initialRDD = s.context.sparkContext.makeRDD(initial)
+      val updateFunc = (values: Seq[Int], state: Option[Int]) => {
+        Some(values.sum + state.getOrElse(0))
+      }
+      val newUpdateFunc = (iterator: Iterator[(String, Seq[Int], Option[Int])]) => {
+        iterator.flatMap(t => updateFunc(t._2, t._3).map(s => (t._1, s)))
+      }
+      s.map(x => (x, 1)).updateStateByKey[Int](newUpdateFunc,
+        new HashPartitioner (numInputPartitions), true, initialRDD)
+    }
+
+    testOperation(inputData, updateStateOperation, outputData, true)
+  }
+
   test("updateStateByKey - object lifecycle") {
     val inputData =
       Seq(