diff options
author | Shubham Chopra <schopra31@bloomberg.net> | 2016-09-30 18:24:39 -0700 |
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committer | Reynold Xin <rxin@databricks.com> | 2016-09-30 18:24:39 -0700 |
commit | a26afd52198523dbd51dc94053424494638c7de5 (patch) | |
tree | d86b827d9c5da5246597479d9428f9c3b5dea657 /core/src/main/scala | |
parent | 81455a9cd963098613bad10182e3fafc83a6e352 (diff) | |
download | spark-a26afd52198523dbd51dc94053424494638c7de5.tar.gz spark-a26afd52198523dbd51dc94053424494638c7de5.tar.bz2 spark-a26afd52198523dbd51dc94053424494638c7de5.zip |
[SPARK-15353][CORE] Making peer selection for block replication pluggable
## What changes were proposed in this pull request?
This PR makes block replication strategies pluggable. It provides two trait that can be implemented, one that maps a host to its topology and is used in the master, and the second that helps prioritize a list of peers for block replication and would run in the executors.
This patch contains default implementations of these traits that make sure current Spark behavior is unchanged.
## How was this patch tested?
This patch should not change Spark behavior in any way, and was tested with unit tests for storage.
Author: Shubham Chopra <schopra31@bloomberg.net>
Closes #13152 from shubhamchopra/RackAwareBlockReplication.
Diffstat (limited to 'core/src/main/scala')
6 files changed, 348 insertions, 99 deletions
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManager.scala b/core/src/main/scala/org/apache/spark/storage/BlockManager.scala index aa29acfd70..982b83324e 100644 --- a/core/src/main/scala/org/apache/spark/storage/BlockManager.scala +++ b/core/src/main/scala/org/apache/spark/storage/BlockManager.scala @@ -20,7 +20,8 @@ package org.apache.spark.storage import java.io._ import java.nio.ByteBuffer -import scala.collection.mutable.{ArrayBuffer, HashMap} +import scala.collection.mutable +import scala.collection.mutable.HashMap import scala.concurrent.{Await, ExecutionContext, Future} import scala.concurrent.duration._ import scala.reflect.ClassTag @@ -44,6 +45,7 @@ import org.apache.spark.unsafe.Platform import org.apache.spark.util._ import org.apache.spark.util.io.ChunkedByteBuffer + /* Class for returning a fetched block and associated metrics. */ private[spark] class BlockResult( val data: Iterator[Any], @@ -147,6 +149,8 @@ private[spark] class BlockManager( private val peerFetchLock = new Object private var lastPeerFetchTime = 0L + private var blockReplicationPolicy: BlockReplicationPolicy = _ + /** * Initializes the BlockManager with the given appId. This is not performed in the constructor as * the appId may not be known at BlockManager instantiation time (in particular for the driver, @@ -160,8 +164,24 @@ private[spark] class BlockManager( blockTransferService.init(this) shuffleClient.init(appId) - blockManagerId = BlockManagerId( - executorId, blockTransferService.hostName, blockTransferService.port) + blockReplicationPolicy = { + val priorityClass = conf.get( + "spark.storage.replication.policy", classOf[RandomBlockReplicationPolicy].getName) + val clazz = Utils.classForName(priorityClass) + val ret = clazz.newInstance.asInstanceOf[BlockReplicationPolicy] + logInfo(s"Using $priorityClass for block replication policy") + ret + } + + val id = + BlockManagerId(executorId, blockTransferService.hostName, blockTransferService.port, None) + + val idFromMaster = master.registerBlockManager( + id, + maxMemory, + slaveEndpoint) + + blockManagerId = if (idFromMaster != null) idFromMaster else id shuffleServerId = if (externalShuffleServiceEnabled) { logInfo(s"external shuffle service port = $externalShuffleServicePort") @@ -170,12 +190,12 @@ private[spark] class BlockManager( blockManagerId } - master.registerBlockManager(blockManagerId, maxMemory, slaveEndpoint) - // Register Executors' configuration with the local shuffle service, if one should exist. if (externalShuffleServiceEnabled && !blockManagerId.isDriver) { registerWithExternalShuffleServer() } + + logInfo(s"Initialized BlockManager: $blockManagerId") } private def registerWithExternalShuffleServer() { @@ -1111,7 +1131,7 @@ private[spark] class BlockManager( } /** - * Replicate block to another node. Not that this is a blocking call that returns after + * Replicate block to another node. Note that this is a blocking call that returns after * the block has been replicated. */ private def replicate( @@ -1119,101 +1139,78 @@ private[spark] class BlockManager( data: ChunkedByteBuffer, level: StorageLevel, classTag: ClassTag[_]): Unit = { + val maxReplicationFailures = conf.getInt("spark.storage.maxReplicationFailures", 1) - val numPeersToReplicateTo = level.replication - 1 - val peersForReplication = new ArrayBuffer[BlockManagerId] - val peersReplicatedTo = new ArrayBuffer[BlockManagerId] - val peersFailedToReplicateTo = new ArrayBuffer[BlockManagerId] val tLevel = StorageLevel( useDisk = level.useDisk, useMemory = level.useMemory, useOffHeap = level.useOffHeap, deserialized = level.deserialized, replication = 1) - val startTime = System.currentTimeMillis - val random = new Random(blockId.hashCode) - - var replicationFailed = false - var failures = 0 - var done = false - - // Get cached list of peers - peersForReplication ++= getPeers(forceFetch = false) - - // Get a random peer. Note that this selection of a peer is deterministic on the block id. - // So assuming the list of peers does not change and no replication failures, - // if there are multiple attempts in the same node to replicate the same block, - // the same set of peers will be selected. - def getRandomPeer(): Option[BlockManagerId] = { - // If replication had failed, then force update the cached list of peers and remove the peers - // that have been already used - if (replicationFailed) { - peersForReplication.clear() - peersForReplication ++= getPeers(forceFetch = true) - peersForReplication --= peersReplicatedTo - peersForReplication --= peersFailedToReplicateTo - } - if (!peersForReplication.isEmpty) { - Some(peersForReplication(random.nextInt(peersForReplication.size))) - } else { - None - } - } - // One by one choose a random peer and try uploading the block to it - // If replication fails (e.g., target peer is down), force the list of cached peers - // to be re-fetched from driver and then pick another random peer for replication. Also - // temporarily black list the peer for which replication failed. - // - // This selection of a peer and replication is continued in a loop until one of the - // following 3 conditions is fulfilled: - // (i) specified number of peers have been replicated to - // (ii) too many failures in replicating to peers - // (iii) no peer left to replicate to - // - while (!done) { - getRandomPeer() match { - case Some(peer) => - try { - val onePeerStartTime = System.currentTimeMillis - logTrace(s"Trying to replicate $blockId of ${data.size} bytes to $peer") - blockTransferService.uploadBlockSync( - peer.host, - peer.port, - peer.executorId, - blockId, - new NettyManagedBuffer(data.toNetty), - tLevel, - classTag) - logTrace(s"Replicated $blockId of ${data.size} bytes to $peer in %s ms" - .format(System.currentTimeMillis - onePeerStartTime)) - peersReplicatedTo += peer - peersForReplication -= peer - replicationFailed = false - if (peersReplicatedTo.size == numPeersToReplicateTo) { - done = true // specified number of peers have been replicated to - } - } catch { - case NonFatal(e) => - logWarning(s"Failed to replicate $blockId to $peer, failure #$failures", e) - failures += 1 - replicationFailed = true - peersFailedToReplicateTo += peer - if (failures > maxReplicationFailures) { // too many failures in replicating to peers - done = true - } + val numPeersToReplicateTo = level.replication - 1 + + val startTime = System.nanoTime + + var peersReplicatedTo = mutable.HashSet.empty[BlockManagerId] + var peersFailedToReplicateTo = mutable.HashSet.empty[BlockManagerId] + var numFailures = 0 + + var peersForReplication = blockReplicationPolicy.prioritize( + blockManagerId, + getPeers(false), + mutable.HashSet.empty, + blockId, + numPeersToReplicateTo) + + while(numFailures <= maxReplicationFailures && + !peersForReplication.isEmpty && + peersReplicatedTo.size != numPeersToReplicateTo) { + val peer = peersForReplication.head + try { + val onePeerStartTime = System.nanoTime + logTrace(s"Trying to replicate $blockId of ${data.size} bytes to $peer") + blockTransferService.uploadBlockSync( + peer.host, + peer.port, + peer.executorId, + blockId, + new NettyManagedBuffer(data.toNetty), + tLevel, + classTag) + logTrace(s"Replicated $blockId of ${data.size} bytes to $peer" + + s" in ${(System.nanoTime - onePeerStartTime).toDouble / 1e6} ms") + peersForReplication = peersForReplication.tail + peersReplicatedTo += peer + } catch { + case NonFatal(e) => + logWarning(s"Failed to replicate $blockId to $peer, failure #$numFailures", e) + peersFailedToReplicateTo += peer + // we have a failed replication, so we get the list of peers again + // we don't want peers we have already replicated to and the ones that + // have failed previously + val filteredPeers = getPeers(true).filter { p => + !peersFailedToReplicateTo.contains(p) && !peersReplicatedTo.contains(p) } - case None => // no peer left to replicate to - done = true + + numFailures += 1 + peersForReplication = blockReplicationPolicy.prioritize( + blockManagerId, + filteredPeers, + peersReplicatedTo, + blockId, + numPeersToReplicateTo - peersReplicatedTo.size) } } - val timeTakeMs = (System.currentTimeMillis - startTime) + logDebug(s"Replicating $blockId of ${data.size} bytes to " + - s"${peersReplicatedTo.size} peer(s) took $timeTakeMs ms") + s"${peersReplicatedTo.size} peer(s) took ${(System.nanoTime - startTime) / 1e6} ms") if (peersReplicatedTo.size < numPeersToReplicateTo) { logWarning(s"Block $blockId replicated to only " + s"${peersReplicatedTo.size} peer(s) instead of $numPeersToReplicateTo peers") } + + logDebug(s"block $blockId replicated to ${peersReplicatedTo.mkString(", ")}") } /** diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala index f255f5be63..c37a3604d2 100644 --- a/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala +++ b/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala @@ -37,10 +37,11 @@ import org.apache.spark.util.Utils class BlockManagerId private ( private var executorId_ : String, private var host_ : String, - private var port_ : Int) + private var port_ : Int, + private var topologyInfo_ : Option[String]) extends Externalizable { - private def this() = this(null, null, 0) // For deserialization only + private def this() = this(null, null, 0, None) // For deserialization only def executorId: String = executorId_ @@ -60,6 +61,8 @@ class BlockManagerId private ( def port: Int = port_ + def topologyInfo: Option[String] = topologyInfo_ + def isDriver: Boolean = { executorId == SparkContext.DRIVER_IDENTIFIER || executorId == SparkContext.LEGACY_DRIVER_IDENTIFIER @@ -69,24 +72,33 @@ class BlockManagerId private ( out.writeUTF(executorId_) out.writeUTF(host_) out.writeInt(port_) + out.writeBoolean(topologyInfo_.isDefined) + // we only write topologyInfo if we have it + topologyInfo.foreach(out.writeUTF(_)) } override def readExternal(in: ObjectInput): Unit = Utils.tryOrIOException { executorId_ = in.readUTF() host_ = in.readUTF() port_ = in.readInt() + val isTopologyInfoAvailable = in.readBoolean() + topologyInfo_ = if (isTopologyInfoAvailable) Option(in.readUTF()) else None } @throws(classOf[IOException]) private def readResolve(): Object = BlockManagerId.getCachedBlockManagerId(this) - override def toString: String = s"BlockManagerId($executorId, $host, $port)" + override def toString: String = s"BlockManagerId($executorId, $host, $port, $topologyInfo)" - override def hashCode: Int = (executorId.hashCode * 41 + host.hashCode) * 41 + port + override def hashCode: Int = + ((executorId.hashCode * 41 + host.hashCode) * 41 + port) * 41 + topologyInfo.hashCode override def equals(that: Any): Boolean = that match { case id: BlockManagerId => - executorId == id.executorId && port == id.port && host == id.host + executorId == id.executorId && + port == id.port && + host == id.host && + topologyInfo == id.topologyInfo case _ => false } @@ -101,10 +113,18 @@ private[spark] object BlockManagerId { * @param execId ID of the executor. * @param host Host name of the block manager. * @param port Port of the block manager. + * @param topologyInfo topology information for the blockmanager, if available + * This can be network topology information for use while choosing peers + * while replicating data blocks. More information available here: + * [[org.apache.spark.storage.TopologyMapper]] * @return A new [[org.apache.spark.storage.BlockManagerId]]. */ - def apply(execId: String, host: String, port: Int): BlockManagerId = - getCachedBlockManagerId(new BlockManagerId(execId, host, port)) + def apply( + execId: String, + host: String, + port: Int, + topologyInfo: Option[String] = None): BlockManagerId = + getCachedBlockManagerId(new BlockManagerId(execId, host, port, topologyInfo)) def apply(in: ObjectInput): BlockManagerId = { val obj = new BlockManagerId() diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala index 8655cf10fc..7a60006891 100644 --- a/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala +++ b/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala @@ -50,12 +50,20 @@ class BlockManagerMaster( logInfo("Removal of executor " + execId + " requested") } - /** Register the BlockManager's id with the driver. */ + /** + * Register the BlockManager's id with the driver. The input BlockManagerId does not contain + * topology information. This information is obtained from the master and we respond with an + * updated BlockManagerId fleshed out with this information. + */ def registerBlockManager( - blockManagerId: BlockManagerId, maxMemSize: Long, slaveEndpoint: RpcEndpointRef): Unit = { + blockManagerId: BlockManagerId, + maxMemSize: Long, + slaveEndpoint: RpcEndpointRef): BlockManagerId = { logInfo(s"Registering BlockManager $blockManagerId") - tell(RegisterBlockManager(blockManagerId, maxMemSize, slaveEndpoint)) - logInfo(s"Registered BlockManager $blockManagerId") + val updatedId = driverEndpoint.askWithRetry[BlockManagerId]( + RegisterBlockManager(blockManagerId, maxMemSize, slaveEndpoint)) + logInfo(s"Registered BlockManager $updatedId") + updatedId } def updateBlockInfo( diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala index 8fa1215011..145c434a4f 100644 --- a/core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala +++ b/core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala @@ -55,10 +55,21 @@ class BlockManagerMasterEndpoint( private val askThreadPool = ThreadUtils.newDaemonCachedThreadPool("block-manager-ask-thread-pool") private implicit val askExecutionContext = ExecutionContext.fromExecutorService(askThreadPool) + private val topologyMapper = { + val topologyMapperClassName = conf.get( + "spark.storage.replication.topologyMapper", classOf[DefaultTopologyMapper].getName) + val clazz = Utils.classForName(topologyMapperClassName) + val mapper = + clazz.getConstructor(classOf[SparkConf]).newInstance(conf).asInstanceOf[TopologyMapper] + logInfo(s"Using $topologyMapperClassName for getting topology information") + mapper + } + + logInfo("BlockManagerMasterEndpoint up") + override def receiveAndReply(context: RpcCallContext): PartialFunction[Any, Unit] = { case RegisterBlockManager(blockManagerId, maxMemSize, slaveEndpoint) => - register(blockManagerId, maxMemSize, slaveEndpoint) - context.reply(true) + context.reply(register(blockManagerId, maxMemSize, slaveEndpoint)) case _updateBlockInfo @ UpdateBlockInfo(blockManagerId, blockId, storageLevel, deserializedSize, size) => @@ -298,7 +309,21 @@ class BlockManagerMasterEndpoint( ).map(_.flatten.toSeq) } - private def register(id: BlockManagerId, maxMemSize: Long, slaveEndpoint: RpcEndpointRef) { + /** + * Returns the BlockManagerId with topology information populated, if available. + */ + private def register( + idWithoutTopologyInfo: BlockManagerId, + maxMemSize: Long, + slaveEndpoint: RpcEndpointRef): BlockManagerId = { + // the dummy id is not expected to contain the topology information. + // we get that info here and respond back with a more fleshed out block manager id + val id = BlockManagerId( + idWithoutTopologyInfo.executorId, + idWithoutTopologyInfo.host, + idWithoutTopologyInfo.port, + topologyMapper.getTopologyForHost(idWithoutTopologyInfo.host)) + val time = System.currentTimeMillis() if (!blockManagerInfo.contains(id)) { blockManagerIdByExecutor.get(id.executorId) match { @@ -318,6 +343,7 @@ class BlockManagerMasterEndpoint( id, System.currentTimeMillis(), maxMemSize, slaveEndpoint) } listenerBus.post(SparkListenerBlockManagerAdded(time, id, maxMemSize)) + id } private def updateBlockInfo( diff --git a/core/src/main/scala/org/apache/spark/storage/BlockReplicationPolicy.scala b/core/src/main/scala/org/apache/spark/storage/BlockReplicationPolicy.scala new file mode 100644 index 0000000000..bf087af16a --- /dev/null +++ b/core/src/main/scala/org/apache/spark/storage/BlockReplicationPolicy.scala @@ -0,0 +1,112 @@ +/* + * 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 scala.collection.mutable +import scala.util.Random + +import org.apache.spark.annotation.DeveloperApi +import org.apache.spark.internal.Logging + +/** + * ::DeveloperApi:: + * BlockReplicationPrioritization provides logic for prioritizing a sequence of peers for + * replicating blocks. BlockManager will replicate to each peer returned in order until the + * desired replication order is reached. If a replication fails, prioritize() will be called + * again to get a fresh prioritization. + */ +@DeveloperApi +trait BlockReplicationPolicy { + + /** + * Method to prioritize a bunch of candidate peers of a block + * + * @param blockManagerId Id of the current BlockManager for self identification + * @param peers A list of peers of a BlockManager + * @param peersReplicatedTo Set of peers already replicated to + * @param blockId BlockId of the block being replicated. This can be used as a source of + * randomness if needed. + * @param numReplicas Number of peers we need to replicate to + * @return A prioritized list of peers. Lower the index of a peer, higher its priority. + * This returns a list of size at most `numPeersToReplicateTo`. + */ + def prioritize( + blockManagerId: BlockManagerId, + peers: Seq[BlockManagerId], + peersReplicatedTo: mutable.HashSet[BlockManagerId], + blockId: BlockId, + numReplicas: Int): List[BlockManagerId] +} + +@DeveloperApi +class RandomBlockReplicationPolicy + extends BlockReplicationPolicy + with Logging { + + /** + * Method to prioritize a bunch of candidate peers of a block. This is a basic implementation, + * that just makes sure we put blocks on different hosts, if possible + * + * @param blockManagerId Id of the current BlockManager for self identification + * @param peers A list of peers of a BlockManager + * @param peersReplicatedTo Set of peers already replicated to + * @param blockId BlockId of the block being replicated. This can be used as a source of + * randomness if needed. + * @return A prioritized list of peers. Lower the index of a peer, higher its priority + */ + override def prioritize( + blockManagerId: BlockManagerId, + peers: Seq[BlockManagerId], + peersReplicatedTo: mutable.HashSet[BlockManagerId], + blockId: BlockId, + numReplicas: Int): List[BlockManagerId] = { + val random = new Random(blockId.hashCode) + logDebug(s"Input peers : ${peers.mkString(", ")}") + val prioritizedPeers = if (peers.size > numReplicas) { + getSampleIds(peers.size, numReplicas, random).map(peers(_)) + } else { + if (peers.size < numReplicas) { + logWarning(s"Expecting ${numReplicas} replicas with only ${peers.size} peer/s.") + } + random.shuffle(peers).toList + } + logDebug(s"Prioritized peers : ${prioritizedPeers.mkString(", ")}") + prioritizedPeers + } + + /** + * Uses sampling algorithm by Robert Floyd. Finds a random sample in O(n) while + * minimizing space usage + * [[http://math.stackexchange.com/questions/178690/ + * whats-the-proof-of-correctness-for-robert-floyds-algorithm-for-selecting-a-sin]] + * + * @param n total number of indices + * @param m number of samples needed + * @param r random number generator + * @return list of m random unique indices + */ + private def getSampleIds(n: Int, m: Int, r: Random): List[Int] = { + val indices = (n - m + 1 to n).foldLeft(Set.empty[Int]) {case (set, i) => + val t = r.nextInt(i) + 1 + if (set.contains(t)) set + i else set + t + } + // we shuffle the result to ensure a random arrangement within the sample + // to avoid any bias from set implementations + r.shuffle(indices.map(_ - 1).toList) + } +} diff --git a/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala b/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala new file mode 100644 index 0000000000..a0f0fdef8e --- /dev/null +++ b/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala @@ -0,0 +1,86 @@ +/* + * 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 : ‘/myrack/myhost’, where ‘/’ is the topology delimiter, + * ‘myrack’ is the topology identifier, and ‘myhost’ 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] +} + +/** + * A TopologyMapper that assumes all nodes are in the same rack + */ +@DeveloperApi +class DefaultTopologyMapper(conf: SparkConf) extends TopologyMapper(conf) with Logging { + override def getTopologyForHost(hostname: String): Option[String] = { + logDebug(s"Got a request for $hostname") + None + } +} + +/** + * A simple file based topology mapper. This expects topology information provided as a + * [[java.util.Properties]] file. The name of the file is obtained from SparkConf property + * `spark.storage.replication.topologyFile`. To use this topology mapper, set the + * `spark.storage.replication.topologyMapper` property to + * [[org.apache.spark.storage.FileBasedTopologyMapper]] + * @param conf SparkConf object + */ +@DeveloperApi +class FileBasedTopologyMapper(conf: SparkConf) extends TopologyMapper(conf) with Logging { + val topologyFile = conf.getOption("spark.storage.replication.topologyFile") + require(topologyFile.isDefined, "Please specify topology file via " + + "spark.storage.replication.topologyFile for FileBasedTopologyMapper.") + val topologyMap = Utils.getPropertiesFromFile(topologyFile.get) + + override def getTopologyForHost(hostname: String): Option[String] = { + val topology = topologyMap.get(hostname) + if (topology.isDefined) { + logDebug(s"$hostname -> ${topology.get}") + } else { + logWarning(s"$hostname does not have any topology information") + } + topology + } +} + |