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/*
* 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 java.util.Timer
import java.util.concurrent.{ScheduledFuture, TimeUnit}
import scala.collection.mutable
import scala.util.control.NonFatal
import org.apache.hadoop.conf.Configuration
import org.apache.spark.SparkEnv
import org.apache.spark.internal.Logging
import org.apache.spark.sql.catalyst.expressions.UnsafeRow
import org.apache.spark.sql.types.StructType
import org.apache.spark.util.ThreadUtils
/** Unique identifier for a [[StateStore]] */
case class StateStoreId(checkpointLocation: String, operatorId: Long, partitionId: Int)
/**
* Base trait for a versioned key-value store used for streaming aggregations
*/
trait StateStore {
/** Unique identifier of the store */
def id: StateStoreId
/** Version of the data in this store before committing updates. */
def version: Long
/** Get the current value of a key. */
def get(key: UnsafeRow): Option[UnsafeRow]
/** Put a new value for a key. */
def put(key: UnsafeRow, value: UnsafeRow)
/**
* Remove keys that match the following condition.
*/
def remove(condition: UnsafeRow => Boolean): Unit
/**
* Commit all the updates that have been made to the store, and return the new version.
*/
def commit(): Long
/** Cancel all the updates that have been made to the store. */
def abort(): Unit
/**
* Iterator of store data after a set of updates have been committed.
* This can be called only after committing all the updates made in the current thread.
*/
def iterator(): Iterator[(UnsafeRow, UnsafeRow)]
/**
* Iterator of the updates that have been committed.
* This can be called only after committing all the updates made in the current thread.
*/
def updates(): Iterator[StoreUpdate]
/**
* Whether all updates have been committed
*/
private[state] def hasCommitted: Boolean
}
/** Trait representing a provider of a specific version of a [[StateStore]]. */
trait StateStoreProvider {
/** Get the store with the existing version. */
def getStore(version: Long): StateStore
/** Optional method for providers to allow for background maintenance */
def doMaintenance(): Unit = { }
}
/** Trait representing updates made to a [[StateStore]]. */
sealed trait StoreUpdate
case class ValueAdded(key: UnsafeRow, value: UnsafeRow) extends StoreUpdate
case class ValueUpdated(key: UnsafeRow, value: UnsafeRow) extends StoreUpdate
case class KeyRemoved(key: UnsafeRow) extends StoreUpdate
/**
* Companion object to [[StateStore]] that provides helper methods to create and retrieve stores
* by their unique ids. In addition, when a SparkContext is active (i.e. SparkEnv.get is not null),
* it also runs a periodic background tasks to do maintenance on the loaded stores. For each
* store, tt uses the [[StateStoreCoordinator]] to ensure whether the current loaded instance of
* the store is the active instance. Accordingly, it either keeps it loaded and performs
* maintenance, or unloads the store.
*/
private[state] object StateStore extends Logging {
val MAINTENANCE_INTERVAL_CONFIG = "spark.streaming.stateStore.maintenanceInterval"
val MAINTENANCE_INTERVAL_DEFAULT_SECS = 60
private val loadedProviders = new mutable.HashMap[StateStoreId, StateStoreProvider]()
private val maintenanceTaskExecutor =
ThreadUtils.newDaemonSingleThreadScheduledExecutor("state-store-maintenance-task")
@volatile private var maintenanceTask: ScheduledFuture[_] = null
@volatile private var _coordRef: StateStoreCoordinatorRef = null
/** Get or create a store associated with the id. */
def get(
storeId: StateStoreId,
keySchema: StructType,
valueSchema: StructType,
version: Long,
storeConf: StateStoreConf,
hadoopConf: Configuration): StateStore = {
require(version >= 0)
val storeProvider = loadedProviders.synchronized {
startMaintenanceIfNeeded()
val provider = loadedProviders.getOrElseUpdate(
storeId,
new HDFSBackedStateStoreProvider(storeId, keySchema, valueSchema, storeConf, hadoopConf))
reportActiveStoreInstance(storeId)
provider
}
storeProvider.getStore(version)
}
/** Unload a state store provider */
def unload(storeId: StateStoreId): Unit = loadedProviders.synchronized {
loadedProviders.remove(storeId)
}
/** Whether a state store provider is loaded or not */
def isLoaded(storeId: StateStoreId): Boolean = loadedProviders.synchronized {
loadedProviders.contains(storeId)
}
/** Unload and stop all state store providers */
def stop(): Unit = loadedProviders.synchronized {
loadedProviders.clear()
_coordRef = null
if (maintenanceTask != null) {
maintenanceTask.cancel(false)
maintenanceTask = null
}
logInfo("StateStore stopped")
}
/** Start the periodic maintenance task if not already started and if Spark active */
private def startMaintenanceIfNeeded(): Unit = loadedProviders.synchronized {
val env = SparkEnv.get
if (maintenanceTask == null && env != null) {
val periodMs = env.conf.getTimeAsMs(
MAINTENANCE_INTERVAL_CONFIG, s"${MAINTENANCE_INTERVAL_DEFAULT_SECS}s")
val runnable = new Runnable {
override def run(): Unit = { doMaintenance() }
}
maintenanceTask = maintenanceTaskExecutor.scheduleAtFixedRate(
runnable, periodMs, periodMs, TimeUnit.MILLISECONDS)
logInfo("State Store maintenance task started")
}
}
/**
* Execute background maintenance task in all the loaded store providers if they are still
* the active instances according to the coordinator.
*/
private def doMaintenance(): Unit = {
logDebug("Doing maintenance")
loadedProviders.synchronized { loadedProviders.toSeq }.foreach { case (id, provider) =>
try {
if (verifyIfStoreInstanceActive(id)) {
provider.doMaintenance()
} else {
unload(id)
logInfo(s"Unloaded $provider")
}
} catch {
case NonFatal(e) =>
logWarning(s"Error managing $provider")
}
}
}
private def reportActiveStoreInstance(storeId: StateStoreId): Unit = {
try {
val host = SparkEnv.get.blockManager.blockManagerId.host
val executorId = SparkEnv.get.blockManager.blockManagerId.executorId
coordinatorRef.foreach(_.reportActiveInstance(storeId, host, executorId))
logDebug(s"Reported that the loaded instance $storeId is active")
} catch {
case NonFatal(e) =>
logWarning(s"Error reporting active instance of $storeId")
}
}
private def verifyIfStoreInstanceActive(storeId: StateStoreId): Boolean = {
try {
val executorId = SparkEnv.get.blockManager.blockManagerId.executorId
val verified =
coordinatorRef.map(_.verifyIfInstanceActive(storeId, executorId)).getOrElse(false)
logDebug(s"Verified whether the loaded instance $storeId is active: $verified" )
verified
} catch {
case NonFatal(e) =>
logWarning(s"Error verifying active instance of $storeId")
false
}
}
private def coordinatorRef: Option[StateStoreCoordinatorRef] = synchronized {
val env = SparkEnv.get
if (env != null) {
if (_coordRef == null) {
_coordRef = StateStoreCoordinatorRef.forExecutor(env)
}
logDebug(s"Retrieved reference to StateStoreCoordinator: ${_coordRef}")
Some(_coordRef)
} else {
_coordRef = null
None
}
}
}
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