Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/11645#discussion_r56227488
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/HDFSBackedStateStoreProvider.scala
---
@@ -0,0 +1,454 @@
+/*
+ * 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.sql.execution.streaming.state
+
+import scala.collection.mutable
+import scala.util.Random
+import scala.util.control.NonFatal
+
+import org.apache.hadoop.conf.Configuration
+import org.apache.hadoop.fs.{FileStatus, Path}
+
+import org.apache.spark.{Logging, SparkConf}
+import org.apache.spark.serializer.{DeserializationStream, KryoSerializer,
SerializationStream}
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.JoinedRow
+import org.apache.spark.util.{CompletionIterator, Utils}
+
+
+/**
+ * An implementation of [[StateStoreProvider]] and [[StateStore]] in which
all the data is backed
+ * by files in a HDFS-compatible file system. All updates to the store
has to be done in sets
+ * transactionally, and each set of updates increments the store's
version. These versions can
+ * be used to re-execute the updates (by retries in RDD operations) on the
correct version of
+ * the store, and regenerate the store version.
+ *
+ * Usage:
+ * To update the data in the state store, the following order of
operations are needed.
+ *
+ * - val store = StateStore.get(operatorId, partitionId, version) // to
get the right store
+ * - store.update(...)
+ * - store.remove(...)
+ * - store.commit() // commits all the updates to made with version
number
+ * - store.iterator() // key-value data after last commit as an iterator
+ * - store.updates() // updates made in the last as an iterator
+ *
+ * Fault-tolerance model:
+ * - Every set of updates is written to a delta file before committing.
+ * - The state store is responsible for managing, collapsing and cleaning
up of delta files.
+ * - Multiple attempts to commit the same version of updates must have the
same updates.
+ * - Background management of files ensures that last versions of the
store is always recoverable
+ * to ensure re-executed RDD operations re-apply updates on the correct
past version of the
+ * store.
+ */
+class HDFSBackedStateStoreProvider(
+ val id: StateStoreId,
+ val directory: String,
+ numBatchesToRetain: Int = 2,
+ maxDeltaChainForSnapshots: Int = 10
+ ) extends StateStoreProvider with Logging {
+ type MapType = mutable.HashMap[InternalRow, InternalRow]
+
+ import StateStore._
+
+
+ class HDFSBackedStateStore( val version: Long, mapToUpdate: MapType)
+ extends StateStore {
+
+ trait STATE
+ case object UPDATING extends STATE
+ case object COMMITTED extends STATE
+ case object CANCELLED extends STATE
+
+ private val newVersion = version + 1
+ private val tempDeltaFile = new Path(baseDir,
s"temp-${Random.nextLong}")
+ private val tempDeltaFileStream =
+ serializer.newInstance().serializeStream(fs.create(tempDeltaFile,
true))
+ private val allUpdates = new mutable.HashMap[InternalRow, StoreUpdate]
+
+ @volatile private var state: STATE = UPDATING
+ @volatile private var finalDeltaFile: Path = null
+
+ override def id: StateStoreId = HDFSBackedStateStoreProvider.this.id
+
+ /** Update the value of a key using the value generated by the update
function */
+ override def update(key: InternalRow, updateFunc: Option[InternalRow]
=> InternalRow): Unit = {
+ verify(state == UPDATING, "Cannot update after already committed or
cancelled")
+ val oldValueOption = mapToUpdate.get(key)
+ val value = updateFunc(oldValueOption)
+ mapToUpdate.put(key, value)
+ allUpdates.get(key) match {
+ case Some(ValueAdded(_, _)) =>
+ allUpdates.put(key, ValueAdded(key, value))
+ case Some(ValueUpdated(_, _)) | Some(KeyRemoved(_)) =>
+ allUpdates.put(key, ValueUpdated(key, value))
+ case None =>
+ val update =
+ if (oldValueOption.nonEmpty) ValueUpdated(key, value) else
ValueAdded(key, value)
+ allUpdates.put(key, update)
+ }
+ tempDeltaFileStream.writeObject(ValueUpdated(key, value))
+ }
+
+ /** Remove keys that match the following condition */
+ override def remove(condition: InternalRow => Boolean): Unit = {
+ verify(state == UPDATING, "Cannot remove after already committed or
cancelled")
+ val keyIter = mapToUpdate.keysIterator
+ while (keyIter.hasNext) {
+ val key = keyIter.next
+ if (condition(key)) {
+ mapToUpdate.remove(key)
+ allUpdates.get(key) match {
+ case Some(ValueUpdated(_, _)) | None =>
+ allUpdates.put(key, KeyRemoved(key))
+ case Some(ValueAdded(_, _)) =>
+ allUpdates.remove(key)
+ case Some(KeyRemoved(_)) =>
+ // Remove already in update map, no need to change
+ }
+ tempDeltaFileStream.writeObject(KeyRemoved(key))
+ }
+ }
+ }
+
+ /** Commit all the updates that have been made to the store. */
+ override def commit(): Long = {
+ verify(state == UPDATING, "Cannot commit again after already
committed or cancelled")
+
+ try {
+ tempDeltaFileStream.close()
+ finalDeltaFile = commitUpdates(newVersion, mapToUpdate,
tempDeltaFile)
+ state = COMMITTED
+ newVersion
+ } catch {
+ case NonFatal(e) =>
+ throw new IllegalStateException(
+ s"Error committing version $newVersion into
${HDFSBackedStateStoreProvider.this}", e)
+ }
+ }
+
+ /** Cancel all the updates made on this store. This store will not be
usable any more. */
+ override def cancel(): Unit = {
+ state = CANCELLED
+ if (tempDeltaFileStream != null) {
+ tempDeltaFileStream.close()
+ }
+ if (tempDeltaFile != null && fs.exists(tempDeltaFile)) {
+ fs.delete(tempDeltaFile, true)
+ }
+ }
+
+ /**
+ * Get an iterator of all the store data. This can be called only
after committing the
+ * updates.
+ */
+ override def iterator(): Iterator[InternalRow] = {
+ verify(state == COMMITTED, "Cannot get iterator of store data before
comitting")
+ HDFSBackedStateStoreProvider.this.iterator(newVersion)
+ }
+
+ /**
+ * Get an iterator of all the updates made to the store in the current
version.
+ * This can be called only after committing the updates.
+ */
+ override def updates(): Iterator[StoreUpdate] = {
+ verify(state == COMMITTED, "Cannot get iterator of updates before
committing")
+ allUpdates.valuesIterator
+ }
+
+ /**
+ * Whether all updates have been committed
+ */
+ override def hasCommitted: Boolean = {
+ state == COMMITTED
+ }
+ }
+
+ /** Get the state store for making updates to create a new `version` of
the store. */
+ override def getStore(version: Long): StateStore = synchronized {
+ require(version >= 0, "Version cannot be less than 0")
+ val newMap = new MapType()
+ if (version > 0) {
+ newMap ++= loadMap(version)
+ }
+ new HDFSBackedStateStore(version, newMap)
+ }
+
+ override def manage(): Unit = {
+ try {
+ doSnapshot()
+ cleanup()
+ } catch {
+ case NonFatal(e) =>
+ logWarning(s"Error performing snapshot and cleaning up $this")
+ }
+ }
+
+ override def toString(): String = {
+ s"StateStore[id = (op=${id.operatorId},part=${id.partitionId}), dir =
$baseDir]"
+ }
+
+ /* Internal classes and methods */
+
+ private val loadedMaps = new mutable.HashMap[Long, MapType]
+ private val baseDir = new Path(directory,
s"${id.operatorId}/${id.partitionId.toString}")
+ private val fs = baseDir.getFileSystem(new Configuration())
+ private val serializer = new KryoSerializer(new SparkConf)
+
+ initialize()
+
+ private case class StoreFile(version: Long, path: Path, isSnapshot:
Boolean)
+
+ /** Commit a set of updates to the store with the given new version */
+ private def commitUpdates(newVersion: Long, map: MapType, tempDeltaFile:
Path): Path = {
+ synchronized {
+ val finalDeltaFile = deltaFile(newVersion)
+ fs.rename(tempDeltaFile, finalDeltaFile)
+ loadedMaps.put(newVersion, map)
+ finalDeltaFile
+ }
+ }
+
+ /**
+ * Get iterator of all the data of the latest version of the store.
+ * Note that this will look up the files to determined the latest known
version.
+ */
+ private[state] def latestIterator(): Iterator[InternalRow] =
synchronized {
+ val versionsInFiles = fetchFiles().map(_.version).toSet
+ val versionsLoaded = loadedMaps.keySet
+ val allKnownVersions = versionsInFiles ++ versionsLoaded
+ if (allKnownVersions.nonEmpty) {
+ loadMap(allKnownVersions.max)
+ .iterator
+ .map { case (key, value) => new JoinedRow(key, value) }
+ } else Iterator.empty
+ }
+
+ /** Get iterator of a specific version of the store */
+ private[state] def iterator(version: Long): Iterator[InternalRow] =
synchronized {
+ loadMap(version)
+ .iterator
+ .map { case (key, value) => new JoinedRow(key, value) }
+ }
+
+ /** Initialize the store provider */
+ private def initialize(): Unit = {
+ if (!fs.exists(baseDir)) {
+ fs.mkdirs(baseDir)
+ } else {
+ if (!fs.isDirectory(baseDir)) {
+ throw new IllegalStateException(
+ s"Cannot use $directory for storing state data as" +
+ s"$baseDir already exists and is not a directory")
+ }
+ }
+ }
+
+ /** Load the required version of the map data from the backing files */
+ private def loadMap(version: Long): MapType = {
+ if (version <= 0) return new MapType
+ synchronized { loadedMaps.get(version) }.getOrElse {
+ val mapFromFile = readSnapshotFile(version).getOrElse {
+ val prevMap = loadMap(version - 1)
+ val deltaUpdates = readDeltaFile(version)
+ val newMap = new MapType()
+ newMap ++= prevMap
+ newMap.sizeHint(prevMap.size)
+ while (deltaUpdates.hasNext) {
+ deltaUpdates.next match {
+ case ValueAdded(key, value) => newMap.put(key, value)
+ case ValueUpdated(key, value) => newMap.put(key, value)
+ case KeyRemoved(key) => newMap.remove(key)
+ }
+ }
+ newMap
+ }
+ loadedMaps.put(version, mapFromFile)
+ mapFromFile
+ }
+ }
+
+ private def readDeltaFile(version: Long): Iterator[StoreUpdate] = {
+ val fileToRead = deltaFile(version)
+ if (!fs.exists(fileToRead)) {
+ throw new IllegalStateException(
+ s"Cannot read delta file $fileToRead of $this: $fileToRead does
not exist")
+ }
+ val deser = serializer.newInstance()
+ var deserStream: DeserializationStream = null
+ deserStream = deser.deserializeStream(fs.open(fileToRead))
+ val iter = deserStream.asIterator.asInstanceOf[Iterator[StoreUpdate]]
+ CompletionIterator[StoreUpdate, Iterator[StoreUpdate]](
+ iter, {
+ deserStream.close()
+ })
+ }
+
+ private def writeSnapshotFile(version: Long, map: MapType): Unit = {
+ val fileToWrite = snapshotFile(version)
+ val ser = serializer.newInstance()
+ var outputStream: SerializationStream = null
+ Utils.tryWithSafeFinally {
+ outputStream = ser.serializeStream(fs.create(fileToWrite, false))
+ outputStream.writeAll(map.iterator)
+ } {
+ if (outputStream != null) outputStream.close()
+ }
+ }
+
+ private def readSnapshotFile(version: Long): Option[MapType] = {
+ val fileToRead = snapshotFile(version)
+ if (!fs.exists(fileToRead)) return None
+
+ val deser = serializer.newInstance()
+ val map = new MapType()
+ var deserStream: DeserializationStream = null
+
+ try {
+ deserStream = deser.deserializeStream(fs.open(fileToRead))
+ val iter =
deserStream.asIterator.asInstanceOf[Iterator[(InternalRow, InternalRow)]]
+ while (iter.hasNext) {
+ map += iter.next()
+ }
+ Some(map)
+ } finally {
+ if (deserStream != null) deserStream.close()
+ }
+ }
+
+
+ /** Perform a snapshot of the store to allow delta files to be
consolidated */
+ private def doSnapshot(): Unit = {
+ try {
+ val files = fetchFiles()
+ if (files.nonEmpty) {
+ val lastVersion = files.last.version
+ val deltaFilesForLastVersion =
+ filesForVersion(files, lastVersion).filter(_.isSnapshot == false)
+ synchronized { loadedMaps.get(lastVersion) } match {
+ case Some(map) =>
+ if (deltaFilesForLastVersion.size > maxDeltaChainForSnapshots)
{
+ writeSnapshotFile(lastVersion, map)
+ }
+ case None =>
+ // The last map is not loaded, probably some other instance is
incharge
+ }
+
+ }
+ } catch {
+ case NonFatal(e) =>
+ logWarning(s"Error doing snapshots for $this", e)
+ }
+ }
+
+ /**
+ * Clean up old snapshots and delta files that are not needed any more.
It ensures that last
+ * few versions of the store can be recovered from the files, so
re-executed RDD operations
+ * can re-apply updates on the past versions of the store.
+ */
+ private[state] def cleanup(): Unit = {
+ try {
+ val files = fetchFiles()
+ if (files.nonEmpty) {
+ val earliestVersionToRetain = files.last.version -
numBatchesToRetain
+ if (earliestVersionToRetain > 0) {
+ val earliestFileToRetain = filesForVersion(files,
earliestVersionToRetain).head
+ synchronized {
+ loadedMaps.keys.filter(_ <
earliestVersionToRetain).foreach(loadedMaps.remove)
+ }
+ files.filter(_.version < earliestFileToRetain.version).foreach {
f =>
+ fs.delete(f.path, true)
+ }
+ }
+ }
+ } catch {
+ case NonFatal(e) =>
+ logWarning(s"Error cleaning up files for $this", e)
+ }
+ }
+
+ private def filesForVersion(allFiles: Seq[StoreFile], version: Long):
Seq[StoreFile] = {
+ require(version >= 0)
+ require(allFiles.exists(_.version == version))
+
+ val latestSnapshotFileBeforeVersion = allFiles
+ .filter(_.isSnapshot == true)
+ .takeWhile(_.version <= version)
+ .lastOption
+ val deltaBatchFiles = latestSnapshotFileBeforeVersion match {
+ case Some(snapshotFile) =>
+ val deltaBatchIds = (snapshotFile.version + 1) to version
+
+ val deltaFiles = allFiles.filter { file =>
+ file.version > snapshotFile.version && file.version <= version
+ }
+ verify(
+ deltaFiles.size == version - snapshotFile.version,
+ s"Unexpected list of delta files for version $version:
${deltaFiles.mkString(",")}"
+ )
+ deltaFiles
+
+ case None =>
+ allFiles.takeWhile(_.version <= version)
+ }
+ latestSnapshotFileBeforeVersion.toSeq ++ deltaBatchFiles
+ }
+
+ private def fetchFiles(): Seq[StoreFile] = {
--- End diff --
add docs.
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