Github user rxin commented on a diff in the pull request: https://github.com/apache/spark/pull/13152#discussion_r76170799 --- Diff: core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala --- @@ -0,0 +1,82 @@ +/* + * 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.storage + +import org.apache.spark.SparkConf +import org.apache.spark.annotation.DeveloperApi +import org.apache.spark.internal.Logging +import org.apache.spark.util.Utils + +/** + * ::DeveloperApi:: + * TopologyMapper provides topology information for a given host + * @param conf SparkConf to get required properties, if needed + */ +@DeveloperApi +abstract class TopologyMapper(conf: SparkConf) { + /** + * Gets the topology information given the host name + * + * @param hostname Hostname + * @return topology information for the given hostname. One can use a 'topology delimiter' + * to make this topology information nested. + * For example : â/myrack/myhostâ, where â/â is the topology delimiter, + * âmyrackâ is the topology identifier, and âmyhostâ is the individual host. + * This function only returns the topology information without the hostname. + * This information can be used when choosing executors for block replication + * to discern executors from a different rack than a candidate executor, for example. + * + * An implementation can choose to use empty strings or None in case topology info + * is not available. This would imply that all such executors belong to the same rack. + */ + def getTopologyForHost(hostname: String): Option[String] +} + +@DeveloperApi +class DefaultTopologyMapper(conf: SparkConf) extends TopologyMapper(conf) with Logging { + override def getTopologyForHost(hostname: String): Option[String] = { + logDebug(s"Got a request for $hostname") + Some("DefaultRack") + } +} + +/** + * A simple file based topology mapper. This expects topology information provided as a + * [[java.util.Properties]] file. The name of the file is obtained from SparkConf property + * `spark.replication.topologyawareness.topologyFile`. To use this topology mapper, set the + * `spark.replication.topologyawareness.topologyMapper` property to + * [[org.apache.spark.storage.FileBasedTopologyMapper]] + * @param conf SparkConf object + */ +@DeveloperApi +class FileBasedTopologyMapper(conf: SparkConf) extends TopologyMapper(conf) with Logging { --- End diff -- can we add a unit test for FileBasedTopologyMapper itself?
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