Github user kayousterhout commented on a diff in the pull request: https://github.com/apache/spark/pull/900#discussion_r14203837 --- Diff: yarn/common/src/main/scala/org/apache/spark/scheduler/cluster/YarnClusterSchedulerBackend.scala --- @@ -0,0 +1,51 @@ +/* + * 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.{Logging, SparkContext} +import org.apache.spark.deploy.yarn.ApplicationMasterArguments +import org.apache.spark.scheduler.TaskSchedulerImpl + +import scala.collection.mutable.ArrayBuffer + +private[spark] class YarnClusterSchedulerBackend( + scheduler: TaskSchedulerImpl, + sc: SparkContext) + extends CoarseGrainedSchedulerBackend(scheduler, sc.env.actorSystem) + with Logging { + + private[spark] def addArg(optionName: String, envVar: String, sysProp: String, + arrayBuf: ArrayBuffer[String]) { + if (System.getenv(envVar) != null) { + arrayBuf += (optionName, System.getenv(envVar)) + } else if (sc.getConf.contains(sysProp)) { + arrayBuf += (optionName, sc.getConf.get(sysProp)) + } + } + + override def start() { + super.start() + val argsArrayBuf = new ArrayBuffer[String]() + List(("--num-executors", "SPARK_EXECUTOR_INSTANCES", "spark.executor.instances"), + ("--num-executors", "SPARK_WORKER_INSTANCES", "spark.worker.instances")) + .foreach { case (optName, envVar, sysProp) => addArg(optName, envVar, sysProp, argsArrayBuf) } + val args = new ApplicationMasterArguments(argsArrayBuf.toArray) + totalExecutors.set(args.numExecutors) --- End diff -- Yeah so my point was can you just replace this code and the addArg() function with something simpler that avoids creating this list of options and passing them to ApplicationMasterArguments? So, just check to see if SPARK_EXECUTOR_INSTANCES/SPARK_WORKER_INSTANCES/spark.executor.instances/spark.worker.instances are set and if so, set totalExecutors accordingly?
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