Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/11645#discussion_r56386237
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/HDFSBackedStateStoreProvider.scala
---
@@ -0,0 +1,465 @@
+/*
+ * 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.
+ */
+private[state] 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._
+
+ /** Implementation of [[StateStore]] API which is backed by a
HDFS-compatible file system */
+ class HDFSBackedStateStore( val version: Long, mapToUpdate: MapType)
+ extends StateStore {
+
+ /** Trait and classes representing the internal state of the store */
+ 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(_, _)) =>
+ // Value did not exist in previous version and was added
already, keep it marked as added
+ allUpdates.put(key, ValueAdded(key, value))
+ case Some(ValueUpdated(_, _)) | Some(KeyRemoved(_)) =>
+ // Value existed in prev version and updated/removed, mark it as
updated
+ allUpdates.put(key, ValueUpdated(key, value))
+ case None =>
+ // There was no prior update, so mark this as added or updated
according to its presence
+ // in previous version.
+ 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 =>
+ // Value existed in previous version and maybe was updated,
mark removed
+ allUpdates.put(key, KeyRemoved(key))
+ case Some(ValueAdded(_, _)) =>
+ // Value did not exist in previous version and was added,
should not appear in updates
+ 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)
+ }
+
+ /** Manage backing files, including creating snapshots and cleaning up
old files */
+ override def manage(): Unit = {
--- End diff --
No strong feelings either way, but this is kind of long. How about
`doMaintenance`?
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