spark MapOutputTracker 源码
spark MapOutputTracker 代码
文件路径：/core/src/main/scala/org/apache/spark/MapOutputTracker.scala
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* 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
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.spark
import java.io.{ByteArrayInputStream, InputStream, IOException, ObjectInputStream, ObjectOutputStream}
import java.nio.ByteBuffer
import java.util.concurrent.{ConcurrentHashMap, LinkedBlockingQueue, ThreadPoolExecutor, TimeUnit}
import java.util.concurrent.locks.ReentrantReadWriteLock
import scala.collection.JavaConverters._
import scala.collection.mutable.{HashMap, ListBuffer, Map}
import scala.concurrent.{ExecutionContext, Future}
import scala.concurrent.duration.Duration
import scala.reflect.ClassTag
import scala.util.control.NonFatal
import org.apache.commons.io.output.{ByteArrayOutputStream => ApacheByteArrayOutputStream}
import org.roaringbitmap.RoaringBitmap
import org.apache.spark.broadcast.{Broadcast, BroadcastManager}
import org.apache.spark.internal.Logging
import org.apache.spark.internal.config._
import org.apache.spark.io.CompressionCodec
import org.apache.spark.rpc.{RpcCallContext, RpcEndpoint, RpcEndpointRef, RpcEnv}
import org.apache.spark.scheduler.{MapStatus, MergeStatus, ShuffleOutputStatus}
import org.apache.spark.shuffle.MetadataFetchFailedException
import org.apache.spark.storage.{BlockId, BlockManagerId, ShuffleBlockId, ShuffleMergedBlockId}
import org.apache.spark.util._
import org.apache.spark.util.io.{ChunkedByteBuffer, ChunkedByteBufferOutputStream}
/**
* Helper class used by the [[MapOutputTrackerMaster]] to perform bookkeeping for a single
* ShuffleMapStage.
*
* This class maintains a mapping from map index to `MapStatus`. It also maintains a cache of
* serialized map statuses in order to speed up tasks' requests for map output statuses.
*
* All public methods of this class are thread-safe.
*/
private class ShuffleStatus(
numPartitions: Int,
numReducers: Int = -1) extends Logging {
private val (readLock, writeLock) = {
val lock = new ReentrantReadWriteLock()
(lock.readLock(), lock.writeLock())
}
// All accesses to the following state must be guarded with `withReadLock` or `withWriteLock`.
private def withReadLock[B](fn: => B): B = {
readLock.lock()
try {
fn
} finally {
readLock.unlock()
}
}
private def withWriteLock[B](fn: => B): B = {
writeLock.lock()
try {
fn
} finally {
writeLock.unlock()
}
}
/**
* MapStatus for each partition. The index of the array is the map partition id.
* Each value in the array is the MapStatus for a partition, or null if the partition
* is not available. Even though in theory a task may run multiple times (due to speculation,
* stage retries, etc.), in practice the likelihood of a map output being available at multiple
* locations is so small that we choose to ignore that case and store only a single location
* for each output.
*/
// Exposed for testing
val mapStatuses = new Array[MapStatus](numPartitions)
/**
* Keep the previous deleted MapStatus for recovery.
*/
val mapStatusesDeleted = new Array[MapStatus](numPartitions)
/**
* MergeStatus for each shuffle partition when push-based shuffle is enabled. The index of the
* array is the shuffle partition id (reduce id). Each value in the array is the MergeStatus for
* a shuffle partition, or null if not available. When push-based shuffle is enabled, this array
* provides a reducer oriented view of the shuffle status specifically for the results of
* merging shuffle partition blocks into per-partition merged shuffle files.
*/
val mergeStatuses = if (numReducers > 0) {
new Array[MergeStatus](numReducers)
} else {
Array.empty[MergeStatus]
}
/**
* The cached result of serializing the map statuses array. This cache is lazily populated when
* [[serializedMapStatus]] is called. The cache is invalidated when map outputs are removed.
*/
private[this] var cachedSerializedMapStatus: Array[Byte] = _
/**
* Broadcast variable holding serialized map output statuses array. When [[serializedMapStatus]]
* serializes the map statuses array it may detect that the result is too large to send in a
* single RPC, in which case it places the serialized array into a broadcast variable and then
* sends a serialized broadcast variable instead. This variable holds a reference to that
* broadcast variable in order to keep it from being garbage collected and to allow for it to be
* explicitly destroyed later on when the ShuffleMapStage is garbage-collected.
*/
private[spark] var cachedSerializedBroadcast: Broadcast[Array[Array[Byte]]] = _
/**
* Similar to cachedSerializedMapStatus and cachedSerializedBroadcast, but for MergeStatus.
*/
private[this] var cachedSerializedMergeStatus: Array[Byte] = _
private[this] var cachedSerializedBroadcastMergeStatus: Broadcast[Array[Array[Byte]]] = _
/**
* Counter tracking the number of partitions that have output. This is a performance optimization
* to avoid having to count the number of non-null entries in the `mapStatuses` array and should
* be equivalent to`mapStatuses.count(_ ne null)`.
*/
private[this] var _numAvailableMapOutputs: Int = 0
/**
* Counter tracking the number of MergeStatus results received so far from the shuffle services.
*/
private[this] var _numAvailableMergeResults: Int = 0
private[this] var shufflePushMergerLocations: Seq[BlockManagerId] = Seq.empty
/**
* Register a map output. If there is already a registered location for the map output then it
* will be replaced by the new location.
*/
def addMapOutput(mapIndex: Int, status: MapStatus): Unit = withWriteLock {
if (mapStatuses(mapIndex) == null) {
_numAvailableMapOutputs += 1
invalidateSerializedMapOutputStatusCache()
}
mapStatuses(mapIndex) = status
}
/**
* Update the map output location (e.g. during migration).
*/
def updateMapOutput(mapId: Long, bmAddress: BlockManagerId): Unit = withWriteLock {
try {
val mapStatusOpt = mapStatuses.find(x => x != null && x.mapId == mapId)
mapStatusOpt match {
case Some(mapStatus) =>
logInfo(s"Updating map output for ${mapId} to ${bmAddress}")
mapStatus.updateLocation(bmAddress)
invalidateSerializedMapOutputStatusCache()
case None =>
val index = mapStatusesDeleted.indexWhere(x => x != null && x.mapId == mapId)
if (index >= 0 && mapStatuses(index) == null) {
val mapStatus = mapStatusesDeleted(index)
mapStatus.updateLocation(bmAddress)
mapStatuses(index) = mapStatus
_numAvailableMapOutputs += 1
invalidateSerializedMapOutputStatusCache()
mapStatusesDeleted(index) = null
logInfo(s"Recover ${mapStatus.mapId} ${mapStatus.location}")
} else {
logWarning(s"Asked to update map output ${mapId} for untracked map status.")
}
}
} catch {
case e: java.lang.NullPointerException =>
logWarning(s"Unable to update map output for ${mapId}, status removed in-flight")
}
}
/**
* Remove the map output which was served by the specified block manager.
* This is a no-op if there is no registered map output or if the registered output is from a
* different block manager.
*/
def removeMapOutput(mapIndex: Int, bmAddress: BlockManagerId): Unit = withWriteLock {
logDebug(s"Removing existing map output ${mapIndex} ${bmAddress}")
if (mapStatuses(mapIndex) != null && mapStatuses(mapIndex).location == bmAddress) {
_numAvailableMapOutputs -= 1
mapStatusesDeleted(mapIndex) = mapStatuses(mapIndex)
mapStatuses(mapIndex) = null
invalidateSerializedMapOutputStatusCache()
}
}
/**
* Register a merge result.
*/
def addMergeResult(reduceId: Int, status: MergeStatus): Unit = withWriteLock {
if (mergeStatuses(reduceId) != status) {
_numAvailableMergeResults += 1
invalidateSerializedMergeOutputStatusCache()
}
mergeStatuses(reduceId) = status
}
def registerShuffleMergerLocations(shuffleMergers: Seq[BlockManagerId]): Unit = withWriteLock {
if (shufflePushMergerLocations.isEmpty) {
shufflePushMergerLocations = shuffleMergers
}
}
def removeShuffleMergerLocations(): Unit = withWriteLock {
shufflePushMergerLocations = Nil
}
// TODO support updateMergeResult for similar use cases as updateMapOutput
/**
* Remove the merge result which was served by the specified block manager.
*/
def removeMergeResult(reduceId: Int, bmAddress: BlockManagerId): Unit = withWriteLock {
if (mergeStatuses(reduceId) != null && mergeStatuses(reduceId).location == bmAddress) {
_numAvailableMergeResults -= 1
mergeStatuses(reduceId) = null
invalidateSerializedMergeOutputStatusCache()
}
}
/**
* Removes all shuffle outputs associated with this host. Note that this will also remove
* outputs which are served by an external shuffle server (if one exists).
*/
def removeOutputsOnHost(host: String): Unit = withWriteLock {
logDebug(s"Removing outputs for host ${host}")
removeOutputsByFilter(x => x.host == host)
removeMergeResultsByFilter(x => x.host == host)
}
/**
* Removes all map outputs associated with the specified executor. Note that this will also
* remove outputs which are served by an external shuffle server (if one exists), as they are
* still registered with that execId.
*/
def removeOutputsOnExecutor(execId: String): Unit = withWriteLock {
logDebug(s"Removing outputs for execId ${execId}")
removeOutputsByFilter(x => x.executorId == execId)
}
/**
* Removes all shuffle outputs which satisfies the filter. Note that this will also
* remove outputs which are served by an external shuffle server (if one exists).
*/
def removeOutputsByFilter(f: BlockManagerId => Boolean): Unit = withWriteLock {
for (mapIndex <- mapStatuses.indices) {
if (mapStatuses(mapIndex) != null && f(mapStatuses(mapIndex).location)) {
_numAvailableMapOutputs -= 1
mapStatusesDeleted(mapIndex) = mapStatuses(mapIndex)
mapStatuses(mapIndex) = null
invalidateSerializedMapOutputStatusCache()
}
}
}
/**
* Removes all shuffle merge result which satisfies the filter.
*/
def removeMergeResultsByFilter(f: BlockManagerId => Boolean): Unit = withWriteLock {
for (reduceId <- mergeStatuses.indices) {
if (mergeStatuses(reduceId) != null && f(mergeStatuses(reduceId).location)) {
_numAvailableMergeResults -= 1
mergeStatuses(reduceId) = null
invalidateSerializedMergeOutputStatusCache()
}
}
}
/**
* Number of partitions that have shuffle map outputs.
*/
def numAvailableMapOutputs: Int = withReadLock {
_numAvailableMapOutputs
}
/**
* Number of shuffle partitions that have already been merge finalized when push-based
* is enabled.
*/
def numAvailableMergeResults: Int = withReadLock {
_numAvailableMergeResults
}
/**
* Returns the sequence of partition ids that are missing (i.e. needs to be computed).
*/
def findMissingPartitions(): Seq[Int] = withReadLock {
val missing = (0 until numPartitions).filter(id => mapStatuses(id) == null)
assert(missing.size == numPartitions - _numAvailableMapOutputs,
s"${missing.size} missing, expected ${numPartitions - _numAvailableMapOutputs}")
missing
}
/**
* Serializes the mapStatuses array into an efficient compressed format. See the comments on
* `MapOutputTracker.serializeOutputStatuses()` for more details on the serialization format.
*
* This method is designed to be called multiple times and implements caching in order to speed
* up subsequent requests. If the cache is empty and multiple threads concurrently attempt to
* serialize the map statuses then serialization will only be performed in a single thread and
* all other threads will block until the cache is populated.
*/
def serializedMapStatus(
broadcastManager: BroadcastManager,
isLocal: Boolean,
minBroadcastSize: Int,
conf: SparkConf): Array[Byte] = {
var result: Array[Byte] = null
withReadLock {
if (cachedSerializedMapStatus != null) {
result = cachedSerializedMapStatus
}
}
if (result == null) withWriteLock {
if (cachedSerializedMapStatus == null) {
val serResult = MapOutputTracker.serializeOutputStatuses[MapStatus](
mapStatuses, broadcastManager, isLocal, minBroadcastSize, conf)
cachedSerializedMapStatus = serResult._1
cachedSerializedBroadcast = serResult._2
}
// The following line has to be outside if statement since it's possible that another thread
// initializes cachedSerializedMapStatus in-between `withReadLock` and `withWriteLock`.
result = cachedSerializedMapStatus
}
result
}
/**
* Serializes the mapStatuses and mergeStatuses array into an efficient compressed format.
* See the comments on `MapOutputTracker.serializeOutputStatuses()` for more details
* on the serialization format.
*
* This method is designed to be called multiple times and implements caching in order to speed
* up subsequent requests. If the cache is empty and multiple threads concurrently attempt to
* serialize the statuses array then serialization will only be performed in a single thread and
* all other threads will block until the cache is populated.
*/
def serializedMapAndMergeStatus(
broadcastManager: BroadcastManager,
isLocal: Boolean,
minBroadcastSize: Int,
conf: SparkConf): (Array[Byte], Array[Byte]) = {
val mapStatusesBytes: Array[Byte] =
serializedMapStatus(broadcastManager, isLocal, minBroadcastSize, conf)
var mergeStatusesBytes: Array[Byte] = null
withReadLock {
if (cachedSerializedMergeStatus != null) {
mergeStatusesBytes = cachedSerializedMergeStatus
}
}
if (mergeStatusesBytes == null) withWriteLock {
if (cachedSerializedMergeStatus == null) {
val serResult = MapOutputTracker.serializeOutputStatuses[MergeStatus](
mergeStatuses, broadcastManager, isLocal, minBroadcastSize, conf)
cachedSerializedMergeStatus = serResult._1
cachedSerializedBroadcastMergeStatus = serResult._2
}
// The following line has to be outside if statement since it's possible that another
// thread initializes cachedSerializedMergeStatus in-between `withReadLock` and
// `withWriteLock`.
mergeStatusesBytes = cachedSerializedMergeStatus
}
(mapStatusesBytes, mergeStatusesBytes)
}
// Used in testing.
def hasCachedSerializedBroadcast: Boolean = withReadLock {
cachedSerializedBroadcast != null
}
/**
* Helper function which provides thread-safe access to the mapStatuses array.
* The function should NOT mutate the array.
*/
def withMapStatuses[T](f: Array[MapStatus] => T): T = withReadLock {
f(mapStatuses)
}
def withMergeStatuses[T](f: Array[MergeStatus] => T): T = withReadLock {
f(mergeStatuses)
}
def getShufflePushMergerLocations: Seq[BlockManagerId] = withReadLock {
shufflePushMergerLocations
}
/**
* Clears the cached serialized map output statuses.
*/
def invalidateSerializedMapOutputStatusCache(): Unit = withWriteLock {
if (cachedSerializedBroadcast != null) {
// Prevent errors during broadcast cleanup from crashing the DAGScheduler (see SPARK-21444)
Utils.tryLogNonFatalError {
// Use `blocking = false` so that this operation doesn't hang while trying to send cleanup
// RPCs to dead executors.
cachedSerializedBroadcast.destroy()
}
cachedSerializedBroadcast = null
}
cachedSerializedMapStatus = null
}
/**
* Clears the cached serialized merge result statuses.
*/
def invalidateSerializedMergeOutputStatusCache(): Unit = withWriteLock {
if (cachedSerializedBroadcastMergeStatus != null) {
Utils.tryLogNonFatalError {
// Use `blocking = false` so that this operation doesn't hang while trying to send cleanup
// RPCs to dead executors.
cachedSerializedBroadcastMergeStatus.destroy()
}
cachedSerializedBroadcastMergeStatus = null
}
cachedSerializedMergeStatus = null
}
}
private[spark] sealed trait MapOutputTrackerMessage
private[spark] case class GetMapOutputStatuses(shuffleId: Int)
extends MapOutputTrackerMessage
private[spark] case class GetMapAndMergeResultStatuses(shuffleId: Int)
extends MapOutputTrackerMessage
private[spark] case class GetShufflePushMergerLocations(shuffleId: Int)
extends MapOutputTrackerMessage
private[spark] case object StopMapOutputTracker extends MapOutputTrackerMessage
private[spark] sealed trait MapOutputTrackerMasterMessage
private[spark] case class GetMapOutputMessage(shuffleId: Int,
context: RpcCallContext) extends MapOutputTrackerMasterMessage
private[spark] case class GetMapAndMergeOutputMessage(shuffleId: Int,
context: RpcCallContext) extends MapOutputTrackerMasterMessage
private[spark] case class GetShufflePushMergersMessage(shuffleId: Int,
context: RpcCallContext) extends MapOutputTrackerMasterMessage
private[spark] case class MapSizesByExecutorId(
iter: Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])], enableBatchFetch: Boolean)
/** RpcEndpoint class for MapOutputTrackerMaster */
private[spark] class MapOutputTrackerMasterEndpoint(
override val rpcEnv: RpcEnv, tracker: MapOutputTrackerMaster, conf: SparkConf)
extends RpcEndpoint with Logging {
logDebug("init") // force eager creation of logger
override def receiveAndReply(context: RpcCallContext): PartialFunction[Any, Unit] = {
case GetMapOutputStatuses(shuffleId: Int) =>
val hostPort = context.senderAddress.hostPort
logInfo(s"Asked to send map output locations for shuffle $shuffleId to $hostPort")
tracker.post(GetMapOutputMessage(shuffleId, context))
case GetMapAndMergeResultStatuses(shuffleId: Int) =>
val hostPort = context.senderAddress.hostPort
logInfo(s"Asked to send map/merge result locations for shuffle $shuffleId to $hostPort")
tracker.post(GetMapAndMergeOutputMessage(shuffleId, context))
case GetShufflePushMergerLocations(shuffleId: Int) =>
logInfo(s"Asked to send shuffle push merger locations for shuffle" +
s" $shuffleId to ${context.senderAddress.hostPort}")
tracker.post(GetShufflePushMergersMessage(shuffleId, context))
case StopMapOutputTracker =>
logInfo("MapOutputTrackerMasterEndpoint stopped!")
context.reply(true)
stop()
}
}
/**
* Class that keeps track of the location of the map output of a stage. This is abstract because the
* driver and executor have different versions of the MapOutputTracker. In principle the driver-
* and executor-side classes don't need to share a common base class; the current shared base class
* is maintained primarily for backwards-compatibility in order to avoid having to update existing
* test code.
*/
private[spark] abstract class MapOutputTracker(conf: SparkConf) extends Logging {
/** Set to the MapOutputTrackerMasterEndpoint living on the driver. */
var trackerEndpoint: RpcEndpointRef = _
/**
* The driver-side counter is incremented every time that a map output is lost. This value is sent
* to executors as part of tasks, where executors compare the new epoch number to the highest
* epoch number that they received in the past. If the new epoch number is higher then executors
* will clear their local caches of map output statuses and will re-fetch (possibly updated)
* statuses from the driver.
*/
protected var epoch: Long = 0
protected val epochLock = new AnyRef
/**
* Send a message to the trackerEndpoint and get its result within a default timeout, or
* throw a SparkException if this fails.
*/
protected def askTracker[T: ClassTag](message: Any): T = {
try {
trackerEndpoint.askSync[T](message)
} catch {
case e: Exception =>
logError("Error communicating with MapOutputTracker", e)
throw new SparkException("Error communicating with MapOutputTracker", e)
}
}
/** Send a one-way message to the trackerEndpoint, to which we expect it to reply with true. */
protected def sendTracker(message: Any): Unit = {
val response = askTracker[Boolean](message)
if (response != true) {
throw new SparkException(
"Error reply received from MapOutputTracker. Expecting true, got " + response.toString)
}
}
// For testing
def getMapSizesByExecutorId(shuffleId: Int, reduceId: Int)
: Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
getMapSizesByExecutorId(shuffleId, 0, Int.MaxValue, reduceId, reduceId + 1)
}
// For testing
def getPushBasedShuffleMapSizesByExecutorId(shuffleId: Int, reduceId: Int)
: MapSizesByExecutorId = {
getPushBasedShuffleMapSizesByExecutorId(shuffleId, 0, Int.MaxValue, reduceId, reduceId + 1)
}
/**
* Called from executors to get the server URIs and output sizes for each shuffle block that
* needs to be read from a given range of map output partitions (startPartition is included but
* endPartition is excluded from the range) within a range of mappers (startMapIndex is included
* but endMapIndex is excluded) when push based shuffle is not enabled for the specific shuffle
* dependency. If endMapIndex=Int.MaxValue, the actual endMapIndex will be changed to the length
* of total map outputs.
*
* @return A sequence of 2-item tuples, where the first item in the tuple is a BlockManagerId,
* and the second item is a sequence of (shuffle block id, shuffle block size, map index)
* tuples describing the shuffle blocks that are stored at that block manager.
* Note that zero-sized blocks are excluded in the result.
*/
def getMapSizesByExecutorId(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])]
/**
* Called from executors to get the server URIs and output sizes for each shuffle block that
* needs to be read from a given range of map output partitions (startPartition is included but
* endPartition is excluded from the range) within a range of mappers (startMapIndex is included
* but endMapIndex is excluded) when push based shuffle is enabled for the specific shuffle
* dependency. If endMapIndex=Int.MaxValue, the actual endMapIndex will be changed to the length
* of total map outputs.
*
* @return A case class object which includes two attributes. The first attribute is a sequence
* of 2-item tuples, where the first item in the tuple is a BlockManagerId, and the
* second item is a sequence of (shuffle block id, shuffle block size, map index) tuples
* tuples describing the shuffle blocks that are stored at that block manager. Note that
* zero-sized blocks are excluded in the result. The second attribute is a boolean flag,
* indicating whether batch fetch can be enabled.
*/
def getPushBasedShuffleMapSizesByExecutorId(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int): MapSizesByExecutorId
/**
* Called from executors upon fetch failure on an entire merged shuffle reduce partition.
* Such failures can happen if the shuffle client fails to fetch the metadata for the given
* merged shuffle partition. This method is to get the server URIs and output sizes for each
* shuffle block that is merged in the specified merged shuffle block so fetch failure on a
* merged shuffle block can fall back to fetching the unmerged blocks.
*
* @return A sequence of 2-item tuples, where the first item in the tuple is a BlockManagerId,
* and the second item is a sequence of (shuffle block ID, shuffle block size, map index)
* tuples describing the shuffle blocks that are stored at that block manager.
*/
def getMapSizesForMergeResult(
shuffleId: Int,
partitionId: Int): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])]
/**
* Called from executors upon fetch failure on a merged shuffle reduce partition chunk. This is
* to get the server URIs and output sizes for each shuffle block that is merged in the specified
* merged shuffle partition chunk so fetch failure on a merged shuffle block chunk can fall back
* to fetching the unmerged blocks.
*
* chunkBitMap tracks the mapIds which are part of the current merged chunk, this way if there is
* a fetch failure on the merged chunk, it can fallback to fetching the corresponding original
* blocks part of this merged chunk.
*
* @return A sequence of 2-item tuples, where the first item in the tuple is a BlockManagerId,
* and the second item is a sequence of (shuffle block ID, shuffle block size, map index)
* tuples describing the shuffle blocks that are stored at that block manager.
*/
def getMapSizesForMergeResult(
shuffleId: Int,
partitionId: Int,
chunkBitmap: RoaringBitmap): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])]
/**
* Called from executors whenever a task with push based shuffle is enabled doesn't have shuffle
* mergers available. This typically happens when the initial stages doesn't have enough shuffle
* mergers available since very few executors got registered. This is on a best effort basis,
* if there is not enough shuffle mergers available for this stage then an empty sequence would
* be returned indicating the task to avoid shuffle push.
* @param shuffleId
*/
def getShufflePushMergerLocations(shuffleId: Int): Seq[BlockManagerId]
/**
* Deletes map output status information for the specified shuffle stage.
*/
def unregisterShuffle(shuffleId: Int): Unit
def stop(): Unit = {}
}
/**
* Driver-side class that keeps track of the location of the map output of a stage.
*
* The DAGScheduler uses this class to (de)register map output statuses and to look up statistics
* for performing locality-aware reduce task scheduling.
*
* ShuffleMapStage uses this class for tracking available / missing outputs in order to determine
* which tasks need to be run.
*/
private[spark] class MapOutputTrackerMaster(
conf: SparkConf,
private[spark] val broadcastManager: BroadcastManager,
private[spark] val isLocal: Boolean)
extends MapOutputTracker(conf) {
// The size at which we use Broadcast to send the map output statuses to the executors
private val minSizeForBroadcast = conf.get(SHUFFLE_MAPOUTPUT_MIN_SIZE_FOR_BROADCAST).toInt
/** Whether to compute locality preferences for reduce tasks */
private val shuffleLocalityEnabled = conf.get(SHUFFLE_REDUCE_LOCALITY_ENABLE)
// Number of map and reduce tasks above which we do not assign preferred locations based on map
// output sizes. We limit the size of jobs for which assign preferred locations as computing the
// top locations by size becomes expensive.
private val SHUFFLE_PREF_MAP_THRESHOLD = 1000
// NOTE: This should be less than 2000 as we use HighlyCompressedMapStatus beyond that
private val SHUFFLE_PREF_REDUCE_THRESHOLD = 1000
// Fraction of total map output that must be at a location for it to considered as a preferred
// location for a reduce task. Making this larger will focus on fewer locations where most data
// can be read locally, but may lead to more delay in scheduling if those locations are busy.
private val REDUCER_PREF_LOCS_FRACTION = 0.2
// HashMap for storing shuffleStatuses in the driver.
// Statuses are dropped only by explicit de-registering.
// Exposed for testing
val shuffleStatuses = new ConcurrentHashMap[Int, ShuffleStatus]().asScala
private val maxRpcMessageSize = RpcUtils.maxMessageSizeBytes(conf)
// requests for MapOutputTrackerMasterMessages
private val mapOutputTrackerMasterMessages =
new LinkedBlockingQueue[MapOutputTrackerMasterMessage]
private val pushBasedShuffleEnabled = Utils.isPushBasedShuffleEnabled(conf, isDriver = true)
// Thread pool used for handling map output status requests. This is a separate thread pool
// to ensure we don't block the normal dispatcher threads.
private val threadpool: ThreadPoolExecutor = {
val numThreads = conf.get(SHUFFLE_MAPOUTPUT_DISPATCHER_NUM_THREADS)
val pool = ThreadUtils.newDaemonFixedThreadPool(numThreads, "map-output-dispatcher")
for (i <- 0 until numThreads) {
pool.execute(new MessageLoop)
}
pool
}
// Make sure that we aren't going to exceed the max RPC message size by making sure
// we use broadcast to send large map output statuses.
if (minSizeForBroadcast > maxRpcMessageSize) {
val msg = s"${SHUFFLE_MAPOUTPUT_MIN_SIZE_FOR_BROADCAST.key} ($minSizeForBroadcast bytes) " +
s"must be <= spark.rpc.message.maxSize ($maxRpcMessageSize bytes) to prevent sending an " +
"rpc message that is too large."
logError(msg)
throw new IllegalArgumentException(msg)
}
def post(message: MapOutputTrackerMasterMessage): Unit = {
mapOutputTrackerMasterMessages.offer(message)
}
/** Message loop used for dispatching messages. */
private class MessageLoop extends Runnable {
private def handleStatusMessage(
shuffleId: Int,
context: RpcCallContext,
needMergeOutput: Boolean): Unit = {
val hostPort = context.senderAddress.hostPort
val shuffleStatus = shuffleStatuses.get(shuffleId).head
logDebug(s"Handling request to send ${if (needMergeOutput) "map" else "map/merge"}" +
s" output locations for shuffle $shuffleId to $hostPort")
if (needMergeOutput) {
context.reply(
shuffleStatus.
serializedMapAndMergeStatus(broadcastManager, isLocal, minSizeForBroadcast, conf))
} else {
context.reply(
shuffleStatus.serializedMapStatus(broadcastManager, isLocal, minSizeForBroadcast, conf))
}
}
override def run(): Unit = {
try {
while (true) {
try {
val data = mapOutputTrackerMasterMessages.take()
if (data == PoisonPill) {
// Put PoisonPill back so that other MessageLoops can see it.
mapOutputTrackerMasterMessages.offer(PoisonPill)
return
}
data match {
case GetMapOutputMessage(shuffleId, context) =>
handleStatusMessage(shuffleId, context, false)
case GetMapAndMergeOutputMessage(shuffleId, context) =>
handleStatusMessage(shuffleId, context, true)
case GetShufflePushMergersMessage(shuffleId, context) =>
logDebug(s"Handling request to send shuffle push merger locations for shuffle" +
s" $shuffleId to ${context.senderAddress.hostPort}")
context.reply(shuffleStatuses.get(shuffleId).map(_.getShufflePushMergerLocations)
.getOrElse(Seq.empty[BlockManagerId]))
}
} catch {
case NonFatal(e) => logError(e.getMessage, e)
}
}
} catch {
case ie: InterruptedException => // exit
}
}
}
/** A poison endpoint that indicates MessageLoop should exit its message loop. */
private val PoisonPill = GetMapOutputMessage(-99, null)
// Used only in unit tests.
private[spark] def getNumCachedSerializedBroadcast: Int = {
shuffleStatuses.valuesIterator.count(_.hasCachedSerializedBroadcast)
}
def registerShuffle(shuffleId: Int, numMaps: Int, numReduces: Int): Unit = {
if (pushBasedShuffleEnabled) {
if (shuffleStatuses.put(shuffleId, new ShuffleStatus(numMaps, numReduces)).isDefined) {
throw new IllegalArgumentException("Shuffle ID " + shuffleId + " registered twice")
}
} else {
if (shuffleStatuses.put(shuffleId, new ShuffleStatus(numMaps)).isDefined) {
throw new IllegalArgumentException("Shuffle ID " + shuffleId + " registered twice")
}
}
}
def updateMapOutput(shuffleId: Int, mapId: Long, bmAddress: BlockManagerId): Unit = {
shuffleStatuses.get(shuffleId) match {
case Some(shuffleStatus) =>
shuffleStatus.updateMapOutput(mapId, bmAddress)
case None =>
logError(s"Asked to update map output for unknown shuffle ${shuffleId}")
}
}
def registerMapOutput(shuffleId: Int, mapIndex: Int, status: MapStatus): Unit = {
shuffleStatuses(shuffleId).addMapOutput(mapIndex, status)
}
/** Unregister map output information of the given shuffle, mapper and block manager */
def unregisterMapOutput(shuffleId: Int, mapIndex: Int, bmAddress: BlockManagerId): Unit = {
shuffleStatuses.get(shuffleId) match {
case Some(shuffleStatus) =>
shuffleStatus.removeMapOutput(mapIndex, bmAddress)
incrementEpoch()
case None =>
throw new SparkException("unregisterMapOutput called for nonexistent shuffle ID")
}
}
/** Unregister all map and merge output information of the given shuffle. */
def unregisterAllMapAndMergeOutput(shuffleId: Int): Unit = {
shuffleStatuses.get(shuffleId) match {
case Some(shuffleStatus) =>
shuffleStatus.removeOutputsByFilter(x => true)
shuffleStatus.removeMergeResultsByFilter(x => true)
shuffleStatus.removeShuffleMergerLocations()
incrementEpoch()
case None =>
throw new SparkException(
s"unregisterAllMapAndMergeOutput called for nonexistent shuffle ID $shuffleId.")
}
}
def registerMergeResult(shuffleId: Int, reduceId: Int, status: MergeStatus): Unit = {
shuffleStatuses(shuffleId).addMergeResult(reduceId, status)
}
def registerMergeResults(shuffleId: Int, statuses: Seq[(Int, MergeStatus)]): Unit = {
statuses.foreach {
case (reduceId, status) => registerMergeResult(shuffleId, reduceId, status)
}
}
def registerShufflePushMergerLocations(
shuffleId: Int,
shuffleMergers: Seq[BlockManagerId]): Unit = {
shuffleStatuses(shuffleId).registerShuffleMergerLocations(shuffleMergers)
}
/**
* Unregisters a merge result corresponding to the reduceId if present. If the optional mapIndex
* is specified, it will only unregister the merge result if the mapIndex is part of that merge
* result.
*
* @param shuffleId the shuffleId.
* @param reduceId the reduceId.
* @param bmAddress block manager address.
* @param mapIndex the optional mapIndex which should be checked to see it was part of the
* merge result.
*/
def unregisterMergeResult(
shuffleId: Int,
reduceId: Int,
bmAddress: BlockManagerId,
mapIndex: Option[Int] = None): Unit = {
shuffleStatuses.get(shuffleId) match {
case Some(shuffleStatus) =>
val mergeStatus = shuffleStatus.mergeStatuses(reduceId)
if (mergeStatus != null &&
(mapIndex.isEmpty || mergeStatus.tracker.contains(mapIndex.get))) {
shuffleStatus.removeMergeResult(reduceId, bmAddress)
incrementEpoch()
}
case None =>
throw new SparkException("unregisterMergeResult called for nonexistent shuffle ID")
}
}
def unregisterAllMergeResult(shuffleId: Int): Unit = {
shuffleStatuses.get(shuffleId) match {
case Some(shuffleStatus) =>
shuffleStatus.removeMergeResultsByFilter(x => true)
incrementEpoch()
case None =>
throw new SparkException(
s"unregisterAllMergeResult called for nonexistent shuffle ID $shuffleId.")
}
}
/** Unregister shuffle data */
def unregisterShuffle(shuffleId: Int): Unit = {
shuffleStatuses.remove(shuffleId).foreach { shuffleStatus =>
// SPARK-39553: Add protection for Scala 2.13 due to https://github.com/scala/bug/issues/12613
// We should revert this if Scala 2.13 solves this issue.
if (shuffleStatus != null) {
shuffleStatus.invalidateSerializedMapOutputStatusCache()
shuffleStatus.invalidateSerializedMergeOutputStatusCache()
}
}
}
/**
* Removes all shuffle outputs associated with this host. Note that this will also remove
* outputs which are served by an external shuffle server (if one exists).
*/
def removeOutputsOnHost(host: String): Unit = {
shuffleStatuses.valuesIterator.foreach { _.removeOutputsOnHost(host) }
incrementEpoch()
}
/**
* Removes all shuffle outputs associated with this executor. Note that this will also remove
* outputs which are served by an external shuffle server (if one exists), as they are still
* registered with this execId.
*/
def removeOutputsOnExecutor(execId: String): Unit = {
shuffleStatuses.valuesIterator.foreach { _.removeOutputsOnExecutor(execId) }
incrementEpoch()
}
/** Check if the given shuffle is being tracked */
def containsShuffle(shuffleId: Int): Boolean = shuffleStatuses.contains(shuffleId)
def getNumAvailableOutputs(shuffleId: Int): Int = {
shuffleStatuses.get(shuffleId).map(_.numAvailableMapOutputs).getOrElse(0)
}
/** VisibleForTest. Invoked in test only. */
private[spark] def getNumAvailableMergeResults(shuffleId: Int): Int = {
shuffleStatuses.get(shuffleId).map(_.numAvailableMergeResults).getOrElse(0)
}
/**
* Returns the sequence of partition ids that are missing (i.e. needs to be computed), or None
* if the MapOutputTrackerMaster doesn't know about this shuffle.
*/
def findMissingPartitions(shuffleId: Int): Option[Seq[Int]] = {
shuffleStatuses.get(shuffleId).map(_.findMissingPartitions())
}
/**
* Grouped function of Range, this is to avoid traverse of all elements of Range using
* IterableLike's grouped function.
*/
def rangeGrouped(range: Range, size: Int): Seq[Range] = {
val start = range.start
val step = range.step
val end = range.end
for (i <- start.until(end, size * step)) yield {
i.until(i + size * step, step)
}
}
/**
* To equally divide n elements into m buckets, basically each bucket should have n/m elements,
* for the remaining n%m elements, add one more element to the first n%m buckets each.
*/
def equallyDivide(numElements: Int, numBuckets: Int): Seq[Seq[Int]] = {
val elementsPerBucket = numElements / numBuckets
val remaining = numElements % numBuckets
val splitPoint = (elementsPerBucket + 1) * remaining
if (elementsPerBucket == 0) {
rangeGrouped(0.until(splitPoint), elementsPerBucket + 1)
} else {
rangeGrouped(0.until(splitPoint), elementsPerBucket + 1) ++
rangeGrouped(splitPoint.until(numElements), elementsPerBucket)
}
}
/**
* Return statistics about all of the outputs for a given shuffle.
*/
def getStatistics(dep: ShuffleDependency[_, _, _]): MapOutputStatistics = {
shuffleStatuses(dep.shuffleId).withMapStatuses { statuses =>
val totalSizes = new Array[Long](dep.partitioner.numPartitions)
val parallelAggThreshold = conf.get(
SHUFFLE_MAP_OUTPUT_PARALLEL_AGGREGATION_THRESHOLD)
val parallelism = math.min(
Runtime.getRuntime.availableProcessors(),
statuses.length.toLong * totalSizes.length / parallelAggThreshold + 1).toInt
if (parallelism <= 1) {
statuses.filter(_ != null).foreach { s =>
for (i <- totalSizes.indices) {
totalSizes(i) += s.getSizeForBlock(i)
}
}
} else {
val threadPool = ThreadUtils.newDaemonFixedThreadPool(parallelism, "map-output-aggregate")
try {
implicit val executionContext = ExecutionContext.fromExecutor(threadPool)
val mapStatusSubmitTasks = equallyDivide(totalSizes.length, parallelism).map {
reduceIds => Future {
statuses.filter(_ != null).foreach { s =>
reduceIds.foreach(i => totalSizes(i) += s.getSizeForBlock(i))
}
}
}
ThreadUtils.awaitResult(Future.sequence(mapStatusSubmitTasks), Duration.Inf)
} finally {
threadPool.shutdown()
}
}
new MapOutputStatistics(dep.shuffleId, totalSizes)
}
}
/**
* Return the preferred hosts on which to run the given map output partition in a given shuffle,
* i.e. the nodes that the most outputs for that partition are on. If the map output is
* pre-merged, then return the node where the merged block is located if the merge ratio is
* above the threshold.
*
* @param dep shuffle dependency object
* @param partitionId map output partition that we want to read
* @return a sequence of host names
*/
def getPreferredLocationsForShuffle(dep: ShuffleDependency[_, _, _], partitionId: Int)
: Seq[String] = {
val shuffleStatus = shuffleStatuses.get(dep.shuffleId).orNull
if (shuffleStatus != null) {
// Check if the map output is pre-merged and if the merge ratio is above the threshold.
// If so, the location of the merged block is the preferred location.
val preferredLoc = if (pushBasedShuffleEnabled) {
shuffleStatus.withMergeStatuses { statuses =>
val status = statuses(partitionId)
val numMaps = dep.rdd.partitions.length
if (status != null && status.getNumMissingMapOutputs(numMaps).toDouble / numMaps
<= (1 - REDUCER_PREF_LOCS_FRACTION)) {
Seq(status.location.host)
} else {
Nil
}
}
} else {
Nil
}
if (preferredLoc.nonEmpty) {
preferredLoc
} else {
if (shuffleLocalityEnabled && dep.rdd.partitions.length < SHUFFLE_PREF_MAP_THRESHOLD &&
dep.partitioner.numPartitions < SHUFFLE_PREF_REDUCE_THRESHOLD) {
val blockManagerIds = getLocationsWithLargestOutputs(dep.shuffleId, partitionId,
dep.partitioner.numPartitions, REDUCER_PREF_LOCS_FRACTION)
if (blockManagerIds.nonEmpty) {
blockManagerIds.get.map(_.host)
} else {
Nil
}
} else {
Nil
}
}
} else {
Nil
}
}
/**
* Return a list of locations that each have fraction of map output greater than the specified
* threshold.
*
* @param shuffleId id of the shuffle
* @param reducerId id of the reduce task
* @param numReducers total number of reducers in the shuffle
* @param fractionThreshold fraction of total map output size that a location must have
* for it to be considered large.
*/
def getLocationsWithLargestOutputs(
shuffleId: Int,
reducerId: Int,
numReducers: Int,
fractionThreshold: Double)
: Option[Array[BlockManagerId]] = {
val shuffleStatus = shuffleStatuses.get(shuffleId).orNull
if (shuffleStatus != null) {
shuffleStatus.withMapStatuses { statuses =>
if (statuses.nonEmpty) {
// HashMap to add up sizes of all blocks at the same location
val locs = new HashMap[BlockManagerId, Long]
var totalOutputSize = 0L
var mapIdx = 0
while (mapIdx < statuses.length) {
val status = statuses(mapIdx)
// status may be null here if we are called between registerShuffle, which creates an
// array with null entries for each output, and registerMapOutputs, which populates it
// with valid status entries. This is possible if one thread schedules a job which
// depends on an RDD which is currently being computed by another thread.
if (status != null) {
val blockSize = status.getSizeForBlock(reducerId)
if (blockSize > 0) {
locs(status.location) = locs.getOrElse(status.location, 0L) + blockSize
totalOutputSize += blockSize
}
}
mapIdx = mapIdx + 1
}
val topLocs = locs.filter { case (loc, size) =>
size.toDouble / totalOutputSize >= fractionThreshold
}
// Return if we have any locations which satisfy the required threshold
if (topLocs.nonEmpty) {
return Some(topLocs.keys.toArray)
}
}
}
}
None
}
/**
* Return the locations where the Mappers ran. The locations each includes both a host and an
* executor id on that host.
*
* @param dep shuffle dependency object
* @param startMapIndex the start map index
* @param endMapIndex the end map index (exclusive)
* @return a sequence of locations where task runs.
*/
def getMapLocation(
dep: ShuffleDependency[_, _, _],
startMapIndex: Int,
endMapIndex: Int): Seq[String] =
{
val shuffleStatus = shuffleStatuses.get(dep.shuffleId).orNull
if (shuffleStatus != null) {
shuffleStatus.withMapStatuses { statuses =>
if (startMapIndex < endMapIndex &&
(startMapIndex >= 0 && endMapIndex <= statuses.length)) {
val statusesPicked = statuses.slice(startMapIndex, endMapIndex).filter(_ != null)
statusesPicked.map(_.location.host).toSeq
} else {
Nil
}
}
} else {
Nil
}
}
def incrementEpoch(): Unit = {
epochLock.synchronized {
epoch += 1
logDebug("Increasing epoch to " + epoch)
}
}
/** Called to get current epoch number. */
def getEpoch: Long = {
epochLock.synchronized {
return epoch
}
}
// This method is only called in local-mode.
override def getMapSizesByExecutorId(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
val mapSizesByExecutorId = getPushBasedShuffleMapSizesByExecutorId(
shuffleId, startMapIndex, endMapIndex, startPartition, endPartition)
assert(mapSizesByExecutorId.enableBatchFetch == true)
mapSizesByExecutorId.iter
}
// This method is only called in local-mode.
override def getPushBasedShuffleMapSizesByExecutorId(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int): MapSizesByExecutorId = {
logDebug(s"Fetching outputs for shuffle $shuffleId")
shuffleStatuses.get(shuffleId) match {
case Some(shuffleStatus) =>
shuffleStatus.withMapStatuses { statuses =>
val actualEndMapIndex = if (endMapIndex == Int.MaxValue) statuses.length else endMapIndex
logDebug(s"Convert map statuses for shuffle $shuffleId, " +
s"mappers $startMapIndex-$actualEndMapIndex, partitions $startPartition-$endPartition")
MapOutputTracker.convertMapStatuses(
shuffleId, startPartition, endPartition, statuses, startMapIndex, actualEndMapIndex)
}
case None =>
MapSizesByExecutorId(Iterator.empty, true)
}
}
// This method is only called in local-mode. Since push based shuffle won't be
// enabled in local-mode, this method returns empty list.
override def getMapSizesForMergeResult(
shuffleId: Int,
partitionId: Int): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
Seq.empty.iterator
}
// This method is only called in local-mode. Since push based shuffle won't be
// enabled in local-mode, this method returns empty list.
override def getMapSizesForMergeResult(
shuffleId: Int,
partitionId: Int,
chunkTracker: RoaringBitmap): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
Seq.empty.iterator
}
// This method is only called in local-mode.
override def getShufflePushMergerLocations(shuffleId: Int): Seq[BlockManagerId] = {
shuffleStatuses(shuffleId).getShufflePushMergerLocations
}
override def stop(): Unit = {
mapOutputTrackerMasterMessages.offer(PoisonPill)
threadpool.shutdown()
try {
sendTracker(StopMapOutputTracker)
} catch {
case e: SparkException =>
logError("Could not tell tracker we are stopping.", e)
}
trackerEndpoint = null
shuffleStatuses.clear()
}
}
/**
* Executor-side client for fetching map output info from the driver's MapOutputTrackerMaster.
* Note that this is not used in local-mode; instead, local-mode Executors access the
* MapOutputTrackerMaster directly (which is possible because the master and worker share a common
* superclass).
*/
private[spark] class MapOutputTrackerWorker(conf: SparkConf) extends MapOutputTracker(conf) {
val mapStatuses: Map[Int, Array[MapStatus]] =
new ConcurrentHashMap[Int, Array[MapStatus]]().asScala
val mergeStatuses: Map[Int, Array[MergeStatus]] =
new ConcurrentHashMap[Int, Array[MergeStatus]]().asScala
// This must be lazy to ensure that it is initialized when the first task is run and not at
// executor startup time. At startup time, user-added libraries may not have been
// downloaded to the executor, causing `isPushBasedShuffleEnabled` to fail when it tries to
// instantiate a serializer. See the followup to SPARK-36705 for more details.
private lazy val fetchMergeResult = Utils.isPushBasedShuffleEnabled(conf, isDriver = false)
/**
* [[shufflePushMergerLocations]] tracks shuffle push merger locations for the latest
* shuffle execution
*
* Exposed for testing
*/
val shufflePushMergerLocations = new ConcurrentHashMap[Int, Seq[BlockManagerId]]().asScala
/**
* A [[KeyLock]] whose key is a shuffle id to ensure there is only one thread fetching
* the same shuffle block.
*/
private val fetchingLock = new KeyLock[Int]
override def getMapSizesByExecutorId(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
val mapSizesByExecutorId = getMapSizesByExecutorIdImpl(
shuffleId, startMapIndex, endMapIndex, startPartition, endPartition, useMergeResult = false)
assert(mapSizesByExecutorId.enableBatchFetch == true)
mapSizesByExecutorId.iter
}
override def getPushBasedShuffleMapSizesByExecutorId(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int): MapSizesByExecutorId = {
getMapSizesByExecutorIdImpl(
shuffleId, startMapIndex, endMapIndex, startPartition, endPartition, useMergeResult = true)
}
private def getMapSizesByExecutorIdImpl(
shuffleId: Int,
startMapIndex: Int,
endMapIndex: Int,
startPartition: Int,
endPartition: Int,
useMergeResult: Boolean): MapSizesByExecutorId = {
logDebug(s"Fetching outputs for shuffle $shuffleId")
val (mapOutputStatuses, mergedOutputStatuses) = getStatuses(shuffleId, conf,
// enableBatchFetch can be set to false during stage retry when the
// shuffleDependency.isShuffleMergeFinalizedMarked is set to false, and Driver
// has already collected the mergedStatus for its shuffle dependency.
// In this case, boolean check helps to ensure that the unnecessary
// mergeStatus won't be fetched, thus mergedOutputStatuses won't be
// passed to convertMapStatuses. See details in [SPARK-37023].
if (useMergeResult) fetchMergeResult else false)
try {
val actualEndMapIndex =
if (endMapIndex == Int.MaxValue) mapOutputStatuses.length else endMapIndex
logDebug(s"Convert map statuses for shuffle $shuffleId, " +
s"mappers $startMapIndex-$actualEndMapIndex, partitions $startPartition-$endPartition")
MapOutputTracker.convertMapStatuses(
shuffleId, startPartition, endPartition, mapOutputStatuses, startMapIndex,
actualEndMapIndex, Option(mergedOutputStatuses))
} catch {
case e: MetadataFetchFailedException =>
// We experienced a fetch failure so our mapStatuses cache is outdated; clear it:
mapStatuses.clear()
mergeStatuses.clear()
throw e
}
}
override def getMapSizesForMergeResult(
shuffleId: Int,
partitionId: Int): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
logDebug(s"Fetching backup outputs for shuffle $shuffleId, partition $partitionId")
// Fetch the map statuses and merge statuses again since they might have already been
// cleared by another task running in the same executor.
val (mapOutputStatuses, mergeResultStatuses) = getStatuses(shuffleId, conf, fetchMergeResult)
try {
val mergeStatus = mergeResultStatuses(partitionId)
// If the original MergeStatus is no longer available, we cannot identify the list of
// unmerged blocks to fetch in this case. Throw MetadataFetchFailedException in this case.
MapOutputTracker.validateStatus(mergeStatus, shuffleId, partitionId)
// Use the MergeStatus's partition level bitmap since we are doing partition level fallback
MapOutputTracker.getMapStatusesForMergeStatus(shuffleId, partitionId,
mapOutputStatuses, mergeStatus.tracker)
} catch {
// We experienced a fetch failure so our mapStatuses cache is outdated; clear it
case e: MetadataFetchFailedException =>
mapStatuses.clear()
mergeStatuses.clear()
throw e
}
}
override def getMapSizesForMergeResult(
shuffleId: Int,
partitionId: Int,
chunkTracker: RoaringBitmap): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
logDebug(s"Fetching backup outputs for shuffle $shuffleId, partition $partitionId")
// Fetch the map statuses and merge statuses again since they might have already been
// cleared by another task running in the same executor.
val (mapOutputStatuses, _) = getStatuses(shuffleId, conf, fetchMergeResult)
try {
MapOutputTracker.getMapStatusesForMergeStatus(shuffleId, partitionId, mapOutputStatuses,
chunkTracker)
} catch {
// We experienced a fetch failure so our mapStatuses cache is outdated; clear it:
case e: MetadataFetchFailedException =>
mapStatuses.clear()
mergeStatuses.clear()
throw e
}
}
override def getShufflePushMergerLocations(shuffleId: Int): Seq[BlockManagerId] = {
shufflePushMergerLocations.getOrElse(shuffleId, getMergerLocations(shuffleId))
}
private def getMergerLocations(shuffleId: Int): Seq[BlockManagerId] = {
fetchingLock.withLock(shuffleId) {
var fetchedMergers = shufflePushMergerLocations.get(shuffleId).orNull
if (null == fetchedMergers) {
fetchedMergers =
askTracker[Seq[BlockManagerId]](GetShufflePushMergerLocations(shuffleId))
if (fetchedMergers.nonEmpty) {
shufflePushMergerLocations(shuffleId) = fetchedMergers
} else {
fetchedMergers = Seq.empty[BlockManagerId]
}
}
fetchedMergers
}
}
/**
* Get or fetch the array of MapStatuses and MergeStatuses if push based shuffle enabled
* for a given shuffle ID. NOTE: clients MUST synchronize
* on this array when reading it, because on the driver, we may be changing it in place.
*
* (It would be nice to remove this restriction in the future.)
*/
private def getStatuses(
shuffleId: Int,
conf: SparkConf,
canFetchMergeResult: Boolean): (Array[MapStatus], Array[MergeStatus]) = {
if (canFetchMergeResult) {
val mapOutputStatuses = mapStatuses.get(shuffleId).orNull
val mergeOutputStatuses = mergeStatuses.get(shuffleId).orNull
if (mapOutputStatuses == null || mergeOutputStatuses == null) {
logInfo("Don't have map/merge outputs for shuffle " + shuffleId + ", fetching them")
val startTimeNs = System.nanoTime()
fetchingLock.withLock(shuffleId) {
var fetchedMapStatuses = mapStatuses.get(shuffleId).orNull
var fetchedMergeStatuses = mergeStatuses.get(shuffleId).orNull
if (fetchedMapStatuses == null || fetchedMergeStatuses == null) {
logInfo("Doing the fetch; tracker endpoint = " + trackerEndpoint)
val fetchedBytes =
askTracker[(Array[Byte], Array[Byte])](GetMapAndMergeResultStatuses(shuffleId))
try {
fetchedMapStatuses =
MapOutputTracker.deserializeOutputStatuses[MapStatus](fetchedBytes._1, conf)
fetchedMergeStatuses =
MapOutputTracker.deserializeOutputStatuses[MergeStatus](fetchedBytes._2, conf)
} catch {
case e: SparkException =>
throw new MetadataFetchFailedException(shuffleId, -1,
s"Unable to deserialize broadcasted map/merge statuses" +
s" for shuffle $shuffleId: " + e.getCause)
}
logInfo("Got the map/merge output locations")
mapStatuses.put(shuffleId, fetchedMapStatuses)
mergeStatuses.put(shuffleId, fetchedMergeStatuses)
}
logDebug(s"Fetching map/merge output statuses for shuffle $shuffleId took " +
s"${TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTimeNs)} ms")
(fetchedMapStatuses, fetchedMergeStatuses)
}
} else {
(mapOutputStatuses, mergeOutputStatuses)
}
} else {
val statuses = mapStatuses.get(shuffleId).orNull
if (statuses == null) {
logInfo("Don't have map outputs for shuffle " + shuffleId + ", fetching them")
val startTimeNs = System.nanoTime()
fetchingLock.withLock(shuffleId) {
var fetchedStatuses = mapStatuses.get(shuffleId).orNull
if (fetchedStatuses == null) {
logInfo("Doing the fetch; tracker endpoint = " + trackerEndpoint)
val fetchedBytes = askTracker[Array[Byte]](GetMapOutputStatuses(shuffleId))
try {
fetchedStatuses =
MapOutputTracker.deserializeOutputStatuses[MapStatus](fetchedBytes, conf)
} catch {
case e: SparkException =>
throw new MetadataFetchFailedException(shuffleId, -1,
s"Unable to deserialize broadcasted map statuses for shuffle $shuffleId: " +
e.getCause)
}
logInfo("Got the map output locations")
mapStatuses.put(shuffleId, fetchedStatuses)
}
logDebug(s"Fetching map output statuses for shuffle $shuffleId took " +
s"${TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTimeNs)} ms")
(fetchedStatuses, null)
}
} else {
(statuses, null)
}
}
}
/** Unregister shuffle data. */
def unregisterShuffle(shuffleId: Int): Unit = {
mapStatuses.remove(shuffleId)
mergeStatuses.remove(shuffleId)
shufflePushMergerLocations.remove(shuffleId)
}
/**
* Called from executors to update the epoch number, potentially clearing old outputs
* because of a fetch failure. Each executor task calls this with the latest epoch
* number on the driver at the time it was created.
*/
def updateEpoch(newEpoch: Long): Unit = {
epochLock.synchronized {
if (newEpoch > epoch) {
logInfo("Updating epoch to " + newEpoch + " and clearing cache")
epoch = newEpoch
mapStatuses.clear()
mergeStatuses.clear()
shufflePushMergerLocations.clear()
}
}
}
}
private[spark] object MapOutputTracker extends Logging {
val ENDPOINT_NAME = "MapOutputTracker"
private val DIRECT = 0
private val BROADCAST = 1
val SHUFFLE_PUSH_MAP_ID = -1
// Serialize an array of map/merge output locations into an efficient byte format so that we can
// send it to reduce tasks. We do this by compressing the serialized bytes using Zstd. They will
// generally be pretty compressible because many outputs will be on the same hostname.
def serializeOutputStatuses[T <: ShuffleOutputStatus](
statuses: Array[T],
broadcastManager: BroadcastManager,
isLocal: Boolean,
minBroadcastSize: Int,
conf: SparkConf): (Array[Byte], Broadcast[Array[Array[Byte]]]) = {
// ByteArrayOutputStream has the 2GB limit so use ChunkedByteBufferOutputStream instead
val out = new ChunkedByteBufferOutputStream(1024 * 1024, ByteBuffer.allocate)
out.write(DIRECT)
val codec = CompressionCodec.createCodec(conf, conf.get(MAP_STATUS_COMPRESSION_CODEC))
val objOut = new ObjectOutputStream(codec.compressedOutputStream(out))
Utils.tryWithSafeFinally {
// Since statuses can be modified in parallel, sync on it
statuses.synchronized {
objOut.writeObject(statuses)
}
} {
objOut.close()
}
val chunkedByteBuf = out.toChunkedByteBuffer
val arrSize = out.size
if (arrSize >= minBroadcastSize) {
// Use broadcast instead.
// Important arr(0) is the tag == DIRECT, ignore that while deserializing !
// arr is a nested Array so that it can handle over 2GB serialized data
val arr = chunkedByteBuf.getChunks().map(_.array())
val bcast = broadcastManager.newBroadcast(arr, isLocal)
// Using `org.apache.commons.io.output.ByteArrayOutputStream` instead of the standard one
// This implementation doesn't reallocate the whole memory block but allocates
// additional buffers. This way no buffers need to be garbage collected and
// the contents don't have to be copied to the new buffer.
val out = new ApacheByteArrayOutputStream()
out.write(BROADCAST)
val oos = new ObjectOutputStream(codec.compressedOutputStream(out))
Utils.tryWithSafeFinally {
oos.writeObject(bcast)
} {
oos.close()
}
val outArr = out.toByteArray
logInfo("Broadcast outputstatuses size = " + outArr.length + ", actual size = " + arrSize)
(outArr, bcast)
} else {
(chunkedByteBuf.toArray, null)
}
}
// Opposite of serializeOutputStatuses.
def deserializeOutputStatuses[T <: ShuffleOutputStatus](
bytes: Array[Byte], conf: SparkConf): Array[T] = {
assert (bytes.length > 0)
def deserializeObject(in: InputStream): AnyRef = {
val codec = CompressionCodec.createCodec(conf, conf.get(MAP_STATUS_COMPRESSION_CODEC))
// The ZStd codec is wrapped in a `BufferedInputStream` which avoids overhead excessive
// of JNI call while trying to decompress small amount of data for each element
// of `MapStatuses`
val objIn = new ObjectInputStream(codec.compressedInputStream(in))
Utils.tryWithSafeFinally {
objIn.readObject()
} {
objIn.close()
}
}
val in = new ByteArrayInputStream(bytes, 1, bytes.length - 1)
bytes(0) match {
case DIRECT =>
deserializeObject(in).asInstanceOf[Array[T]]
case BROADCAST =>
try {
// deserialize the Broadcast, pull .value array out of it, and then deserialize that
val bcast = deserializeObject(in).asInstanceOf[Broadcast[Array[Array[Byte]]]]
logInfo("Broadcast outputstatuses size = " + bytes.length +
", actual size = " + bcast.value.foldLeft(0L)(_ + _.length))
val bcastIn = new ChunkedByteBuffer(bcast.value.map(ByteBuffer.wrap)).toInputStream()
// Important - ignore the DIRECT tag ! Start from offset 1
bcastIn.skip(1)
deserializeObject(bcastIn).asInstanceOf[Array[T]]
} catch {
case e: IOException =>
logWarning("Exception encountered during deserializing broadcasted" +
" output statuses: ", e)
throw new SparkException("Unable to deserialize broadcasted" +
" output statuses", e)
}
case _ => throw new IllegalArgumentException("Unexpected byte tag = " + bytes(0))
}
}
/**
* Given an array of map statuses and a range of map output partitions, returns a sequence that,
* for each block manager ID, lists the shuffle block IDs and corresponding shuffle block sizes
* stored at that block manager.
* Note that empty blocks are filtered in the result.
*
* If push-based shuffle is enabled and an array of merge statuses is available, prioritize
* the locations of the merged shuffle partitions over unmerged shuffle blocks.
*
* If any of the statuses is null (indicating a missing location due to a failed mapper),
* throws a FetchFailedException.
*
* @param shuffleId Identifier for the shuffle
* @param startPartition Start of map output partition ID range (included in range)
* @param endPartition End of map output partition ID range (excluded from range)
* @param mapStatuses List of map statuses, indexed by map partition index.
* @param startMapIndex Start Map index.
* @param endMapIndex End Map index.
* @param mergeStatuses List of merge statuses, index by reduce ID.
* @return A sequence of 2-item tuples, where the first item in the tuple is a BlockManagerId,
* and the second item is a sequence of (shuffle block id, shuffle block size, map index)
* tuples describing the shuffle blocks that are stored at that block manager.
*/
def convertMapStatuses(
shuffleId: Int,
startPartition: Int,
endPartition: Int,
mapStatuses: Array[MapStatus],
startMapIndex : Int,
endMapIndex: Int,
mergeStatusesOpt: Option[Array[MergeStatus]] = None): MapSizesByExecutorId = {
assert (mapStatuses != null)
val splitsByAddress = new HashMap[BlockManagerId, ListBuffer[(BlockId, Long, Int)]]
var enableBatchFetch = true
// Only use MergeStatus for reduce tasks that fetch all map outputs. Since a merged shuffle
// partition consists of blocks merged in random order, we are unable to serve map index
// subrange requests. However, when a reduce task needs to fetch blocks from a subrange of
// map outputs, it usually indicates skewed partitions which push-based shuffle delegates
// to AQE to handle.
// TODO: SPARK-35036: Instead of reading map blocks in case of AQE with Push based shuffle,
// TODO: improve push based shuffle to read partial merged blocks satisfying the start/end
// TODO: map indexes
if (mergeStatusesOpt.exists(_.exists(_ != null)) && startMapIndex == 0
&& endMapIndex == mapStatuses.length) {
enableBatchFetch = false
logDebug(s"Disable shuffle batch fetch as Push based shuffle is enabled for $shuffleId.")
val mergeStatuses = mergeStatusesOpt.get
for (partId <- startPartition until endPartition) {
val mergeStatus = mergeStatuses(partId)
if (mergeStatus != null && mergeStatus.totalSize > 0) {
// If MergeStatus is available for the given partition, add location of the
// pre-merged shuffle partition for this partition ID. Here we create a
// ShuffleMergedBlockId to indicate this is a merged shuffle block.
splitsByAddress.getOrElseUpdate(mergeStatus.location, ListBuffer()) +=
((ShuffleMergedBlockId(shuffleId, mergeStatus.shuffleMergeId, partId),
mergeStatus.totalSize, SHUFFLE_PUSH_MAP_ID))
}
}
// Add location for the mapper shuffle partition blocks
for ((mapStatus, mapIndex) <- mapStatuses.iterator.zipWithIndex) {
validateStatus(mapStatus, shuffleId, startPartition)
for (partId <- startPartition until endPartition) {
// For the "holes" in this pre-merged shuffle partition, i.e., unmerged mapper
// shuffle partition blocks, fetch the original map produced shuffle partition blocks
val mergeStatus = mergeStatuses(partId)
if (mergeStatus == null || mergeStatus.totalSize == 0 ||
!mergeStatus.tracker.contains(mapIndex)) {
val size = mapStatus.getSizeForBlock(partId)
if (size != 0) {
splitsByAddress.getOrElseUpdate(mapStatus.location, ListBuffer()) +=
((ShuffleBlockId(shuffleId, mapStatus.mapId, partId), size, mapIndex))
}
}
}
}
} else {
val iter = mapStatuses.iterator.zipWithIndex
for ((status, mapIndex) <- iter.slice(startMapIndex, endMapIndex)) {
validateStatus(status, shuffleId, startPartition)
for (part <- startPartition until endPartition) {
val size = status.getSizeForBlock(part)
if (size != 0) {
splitsByAddress.getOrElseUpdate(status.location, ListBuffer()) +=
((ShuffleBlockId(shuffleId, status.mapId, part), size, mapIndex))
}
}
}
}
MapSizesByExecutorId(splitsByAddress.mapValues(_.toSeq).iterator, enableBatchFetch)
}
/**
* Given a shuffle ID, a partition ID, an array of map statuses, and bitmap corresponding
* to either a merged shuffle partition or a merged shuffle partition chunk, identify
* the metadata about the shuffle partition blocks that are merged into the merged shuffle
* partition or partition chunk represented by the bitmap.
*
* @param shuffleId Identifier for the shuffle
* @param partitionId The partition ID of the MergeStatus for which we look for the metadata
* of the merged shuffle partition blocks
* @param mapStatuses List of map statuses, indexed by map ID
* @param tracker bitmap containing mapIndexes that belong to the merged block or merged
* block chunk.
* @return A sequence of 2-item tuples, where the first item in the tuple is a BlockManagerId,
* and the second item is a sequence of (shuffle block ID, shuffle block size) tuples
* describing the shuffle blocks that are stored at that block manager.
*/
def getMapStatusesForMergeStatus(
shuffleId: Int,
partitionId: Int,
mapStatuses: Array[MapStatus],
tracker: RoaringBitmap): Iterator[(BlockManagerId, Seq[(BlockId, Long, Int)])] = {
assert (mapStatuses != null && tracker != null)
val splitsByAddress = new HashMap[BlockManagerId, ListBuffer[(BlockId, Long, Int)]]
for ((status, mapIndex) <- mapStatuses.zipWithIndex) {
// Only add blocks that are merged
if (tracker.contains(mapIndex)) {
MapOutputTracker.validateStatus(status, shuffleId, partitionId)
splitsByAddress.getOrElseUpdate(status.location, ListBuffer()) +=
((ShuffleBlockId(shuffleId, status.mapId, partitionId),
status.getSizeForBlock(partitionId), mapIndex))
}
}
splitsByAddress.mapValues(_.toSeq).iterator
}
def validateStatus(status: ShuffleOutputStatus, shuffleId: Int, partition: Int) : Unit = {
if (status == null) {
val errorMessage = s"Missing an output location for shuffle $shuffleId partition $partition"
logError(errorMessage)
throw new MetadataFetchFailedException(shuffleId, partition, errorMessage)
}
}
}
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