Github user tdas commented on a diff in the pull request: https://github.com/apache/spark/pull/9256#discussion_r44205513 --- Diff: streaming/src/main/scala/org/apache/spark/streaming/util/StateMap.scala --- @@ -0,0 +1,304 @@ +/* + * 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.streaming.util + +import java.io.{ObjectInputStream, ObjectOutputStream} + +import scala.reflect.ClassTag + +import org.apache.spark.SparkConf +import org.apache.spark.streaming.util.OpenHashMapBasedStateMap._ +import org.apache.spark.util.collection.OpenHashMap + +/** Internal interface for defining the map that keeps track of sessions. */ +private[streaming] abstract class StateMap[K: ClassTag, S: ClassTag] extends Serializable { + + /** Get the state for a key if it exists */ + def get(key: K): Option[S] + + /** Get all the keys and states whose updated time is older than the given threshold time */ + def getByTime(threshUpdatedTime: Long): Iterator[(K, S, Long)] + + /** Get all the keys and states in this map. */ + def getAll(): Iterator[(K, S, Long)] + + /** Add or update state */ + def put(key: K, state: S, updatedTime: Long): Unit + + /** Remove a key */ + def remove(key: K): Unit + + /** + * Shallow copy `this` map to create a new state map. + * Updates to the new map should not mutate `this` map. + */ + def copy(): StateMap[K, S] + + def toDebugString(): String = toString() +} + +/** Companion object for [[StateMap]], with utility methods */ +private[streaming] object StateMap { + def empty[K: ClassTag, S: ClassTag]: StateMap[K, S] = new EmptyStateMap[K, S] + + def create[K: ClassTag, S: ClassTag](conf: SparkConf): StateMap[K, S] = { + val deltaChainThreshold = conf.getInt("spark.streaming.sessionByKey.deltaChainThreshold", + DELTA_CHAIN_LENGTH_THRESHOLD) + new OpenHashMapBasedStateMap[K, S](64, deltaChainThreshold) + } +} + +/** Specific implementation of SessionStore interface representing an empty map */ +private[streaming] class EmptyStateMap[K: ClassTag, S: ClassTag] extends StateMap[K, S] { + override def put(key: K, session: S, updateTime: Long): Unit = { + throw new NotImplementedError("put() should not be called on an EmptyStateMap") + } + override def get(key: K): Option[S] = None + override def getByTime(threshUpdatedTime: Long): Iterator[(K, S, Long)] = Iterator.empty + override def getAll(): Iterator[(K, S, Long)] = Iterator.empty + override def copy(): StateMap[K, S] = new EmptyStateMap[K, S] + override def remove(key: K): Unit = { } + override def toDebugString(): String = "" +} + + + +/** Implementation of StateMap based on Spark's OpenHashMap */ +private[streaming] class OpenHashMapBasedStateMap[K: ClassTag, S: ClassTag]( + @transient @volatile var parentStateMap: StateMap[K, S], + initialCapacity: Int = 64, + deltaChainThreshold: Int = DELTA_CHAIN_LENGTH_THRESHOLD + ) extends StateMap[K, S] { self => + + def this(initialCapacity: Int, deltaChainThreshold: Int) = this( + new EmptyStateMap[K, S], + initialCapacity = initialCapacity, + deltaChainThreshold = deltaChainThreshold) + + def this(deltaChainThreshold: Int) = this( + initialCapacity = 64, deltaChainThreshold = deltaChainThreshold) + + def this() = this(DELTA_CHAIN_LENGTH_THRESHOLD) + + @transient @volatile private var deltaMap = + new OpenHashMap[K, StateInfo[S]](initialCapacity) + + /** Get the session data if it exists */ + override def get(key: K): Option[S] = { + val stateInfo = deltaMap(key) + if (stateInfo != null) { + if (!stateInfo.deleted) { + Some(stateInfo.data) + } else { + None + } + } else { + parentStateMap.get(key) + } + } + + /** Get all the keys and states whose updated time is older than the give threshold time */ + override def getByTime(threshUpdatedTime: Long): Iterator[(K, S, Long)] = { + val oldStates = parentStateMap.getByTime(threshUpdatedTime).filter { case (key, value, _) => + !deltaMap.contains(key) + } + + val updatedStates = deltaMap.iterator.flatMap { case (key, stateInfo) => --- End diff -- both will exhaust the iterator. I think the concern is just readability. I am changing it.
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