Github user tejasapatil commented on a diff in the pull request:
https://github.com/apache/spark/pull/15541#discussion_r83995590
--- Diff: core/src/main/scala/org/apache/spark/scheduler/TaskAssigner.scala
---
@@ -0,0 +1,233 @@
+/*
+ * 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.scheduler
+
+import scala.collection.mutable.ArrayBuffer
+import scala.collection.mutable.PriorityQueue
+import scala.util.Random
+
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.SparkConf
+import org.apache.spark.util.Utils
+
+/** Tracking the current state of the workers with available cores and
assigned task list. */
+class OfferState(val workOffer: WorkerOffer) {
+ // The current remaining cores that can be allocated to tasks.
+ var coresAvailable: Int = workOffer.cores
+ // The list of tasks that are assigned to this worker.
+ val tasks = new ArrayBuffer[TaskDescription](coresAvailable)
+}
+
+/**
+ * TaskAssigner is the base class for all task assigner implementations,
and can be
+ * extended to implement different task scheduling algorithms.
+ * Together with [[org.apache.spark.scheduler.TaskScheduler
TaskScheduler]], TaskAssigner
+ * is used to assign tasks to workers with available cores. Internally,
TaskScheduler, requested
+ * to perform task assignment given available workers, first sorts the
candidate tasksets,
+ * and then for each taskset, it takes a number of rounds to request
TaskAssigner for task
+ * assignment with different the locality restrictions until there is
either no qualified
+ * workers or no valid tasks to be assigned.
+ *
+ * TaskAssigner is responsible to maintain the worker availability state
and task assignment
+ * information. The contract between
[[org.apache.spark.scheduler.TaskScheduler TaskScheduler]]
+ * and TaskAssigner is as follows. First, TaskScheduler invokes
construct() of TaskAssigner to
+ * initialize the its internal worker states at the beginning of resource
offering. Before each
+ * round of task assignment for a taskset, TaskScheduler invoke the init()
of TaskAssigner to
+ * initialize the data structure for the round. When performing real task
assignment,
+ * hasNext()/getNext() is used by TaskScheduler to check the worker
availability and retrieve
+ * current offering from TaskAssigner. Then offerAccepted is used by
TaskScheduler to notify
+ * the TaskAssigner so that TaskAssigner can decide whether the current
offer is valid or not for
+ * the next request. After task assignment is done, TaskScheduler invokes
the tasks() to
+ * retrieve all the task assignment information, and eventually, invokes
reset() method so that
+ * TaskAssigner can cleanup its internal maintained resources.
+ */
+
+private[scheduler] abstract class TaskAssigner {
+ var offer: Seq[OfferState] = _
+ var CPUS_PER_TASK = 1
--- End diff --
- nit: use `protected`
- nit: Why camel case ? This looks like an regular class var and not a
constant. I know you want this to be treated as a constant but probably should
have better guarding against that
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