Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/9256#discussion_r44094830
--- 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]
--- End diff --
nit: this method can return `this` since it's immutable.
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