Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/7276#discussion_r35287619
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverSchedulingPolicy.scala
---
@@ -0,0 +1,161 @@
+/*
+ * 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.scheduler
+
+import scala.collection.Map
+import scala.collection.mutable
+
+import org.apache.spark.streaming.receiver.Receiver
+
+private[streaming] class ReceiverSchedulingPolicy {
+
+ /**
+ * Try our best to schedule receivers with evenly distributed. However,
if the
+ * `preferredLocation`s of receivers are not even, we may not be able to
schedule them evenly
+ * because we have to respect them.
+ *
+ * This method is called when we start to launch receivers at the first
time.
+ */
+ def scheduleReceivers(
+ receivers: Seq[Receiver[_]], executors: Seq[String]): Map[Int,
Seq[String]] = {
+ if (receivers.isEmpty) {
+ return Map.empty
+ }
+
+ if (executors.isEmpty) {
+ return receivers.map(_.streamId -> Seq.empty).toMap
+ }
+
+ val hostToExecutors = executors.groupBy(_.split(":")(0))
+ val locations = new
Array[mutable.ArrayBuffer[String]](receivers.length)
+ val numReceiversOnExecutor = mutable.HashMap[String, Int]()
+ // Set the initial value to 0
+ executors.foreach(numReceiversOnExecutor(_) = 0)
--- End diff --
nit: A little easier to read if written as `executors.foreach { e =>
numReceiversOnExecutor(e) = 1 }
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