Github user tgravescs commented on a diff in the pull request: https://github.com/apache/spark/pull/900#discussion_r14265985 --- Diff: yarn/common/src/main/scala/org/apache/spark/scheduler/cluster/YarnClusterSchedulerBackend.scala --- @@ -0,0 +1,39 @@ +/* + * 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.cluster + +import org.apache.spark.SparkContext +import org.apache.spark.scheduler.TaskSchedulerImpl +import org.apache.spark.util.IntParam + +private[spark] class YarnClusterSchedulerBackend( + scheduler: TaskSchedulerImpl, + sc: SparkContext) + extends CoarseGrainedSchedulerBackend(scheduler, sc.env.actorSystem) { + + override def start() { + super.start() + var numExecutors = 2 + if (sc.getConf.contains("spark.executor.instances")) { + numExecutors = sc.getConf.getInt("spark.executor.instances", 2) + } else if (System.getenv("SPARK_EXECUTOR_INSTANCES") != null) { + IntParam.unapply(System.getenv("SPARK_EXECUTOR_INSTANCES")).map(_.toInt).getOrElse(2) --- End diff -- well the SPARK_WORKER_INSTANCES env variables was only using in yarn-client mode so isn't strictly needed here since this class is backend for yarn-cluster mode.. I assume that is why it was removed. Something I hadn't thought of when you first asked.
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