Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/13152#discussion_r76170605
--- 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 {
+ val topologyFile =
conf.getOption("spark.replication.topologyawareness.topologyfile")
+ require(topologyFile.isDefined, "Please provide topology file for
FileBasedTopologyMapper.")
--- End diff --
"Please specify topology file via spark.storage.replication.topologyFile
for FileBasedTopologyMapper."
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