Github user arunmahadevan commented on a diff in the pull request:
https://github.com/apache/spark/pull/21337#discussion_r188682238
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/continuous/shuffle/ContinuousShuffleReadRDD.scala
---
@@ -0,0 +1,64 @@
+/*
+ * 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.sql.execution.streaming.continuous.shuffle
+
+import java.util.UUID
+
+import org.apache.spark.{Partition, SparkContext, SparkEnv, TaskContext}
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
+import org.apache.spark.util.NextIterator
+
+case class ContinuousShuffleReadPartition(index: Int) extends Partition {
+ // Initialized only on the executor, and only once even as we call
compute() multiple times.
+ lazy val (receiver, endpoint) = {
+ val env = SparkEnv.get.rpcEnv
+ val receiver = new UnsafeRowReceiver(env)
+ val endpoint = env.setupEndpoint(UUID.randomUUID().toString, receiver)
+ TaskContext.get().addTaskCompletionListener { ctx =>
+ env.stop(endpoint)
+ }
+ (receiver, endpoint)
+ }
+}
+
+/**
+ * RDD at the bottom of each continuous processing shuffle task, reading
from the
+ */
+class ContinuousShuffleReadRDD(sc: SparkContext, numPartitions: Int)
+ extends RDD[UnsafeRow](sc, Nil) {
+
+ override protected def getPartitions: Array[Partition] = {
+ (0 until numPartitions).map(ContinuousShuffleReadPartition).toArray
+ }
+
+ override def compute(split: Partition, context: TaskContext):
Iterator[UnsafeRow] = {
+ val receiver =
split.asInstanceOf[ContinuousShuffleReadPartition].receiver
+
+ new NextIterator[UnsafeRow] {
+ override def getNext(): UnsafeRow = receiver.poll() match {
+ case ReceiverRow(r) => r
+ case ReceiverEpochMarker() =>
--- End diff --
If the task does not wait for markers from all its children, it would not
guarantee at-least once.
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