Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/126#discussion_r10950330
--- Diff:
core/src/main/scala/org/apache/spark/util/TimeStampedWeakValueHashMap.scala ---
@@ -0,0 +1,133 @@
+/*
+ * 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.util
+
+import scala.collection.{JavaConversions, immutable}
+
+import java.util
+import java.lang.ref.WeakReference
+import java.util.concurrent.ConcurrentHashMap
+
+import org.apache.spark.Logging
+import java.util.concurrent.atomic.AtomicInteger
+
+private[util] case class TimeStampedWeakValue[T](timestamp: Long,
weakValue: WeakReference[T]) {
+ def this(timestamp: Long, value: T) = this(timestamp, new
WeakReference[T](value))
+}
+
+/**
+ * A map that stores the timestamp of when a key was inserted along with
the value,
+ * while ensuring that the values are weakly referenced. If the value is
garbage collected and
+ * the weak reference is null, get() operation returns the key be
non-existent. However,
+ * the key is actually not removed in the current implementation.
Key-value pairs whose
+ * timestamps are older than a particular threshold time can then be
removed using the
+ * clearOldValues method. It exposes a scala.collection.mutable.Map
interface to allow it to be a
+ * drop-in replacement for Scala HashMaps.
+ *
+ * Internally, it uses a Java ConcurrentHashMap, so all operations on this
HashMap are thread-safe.
+ */
+
+private[spark] class TimeStampedWeakValueHashMap[A, B]()
+ extends WrappedJavaHashMap[A, B, A, TimeStampedWeakValue[B]] with
Logging {
+
+ /** Number of inserts after which keys whose weak ref values are null
will be cleaned */
+ private val CLEANUP_INTERVAL = 1000
+
+ /** Counter for counting the number of inserts */
+ private val insertCounts = new AtomicInteger(0)
+
+ protected[util] val internalJavaMap: util.Map[A,
TimeStampedWeakValue[B]] = {
+ new ConcurrentHashMap[A, TimeStampedWeakValue[B]]()
+ }
+
+ protected[util] def newInstance[K1, V1](): WrappedJavaHashMap[K1, V1, _,
_] = {
+ new TimeStampedWeakValueHashMap[K1, V1]()
+ }
+
+ override def +=(kv: (A, B)): this.type = {
+ // Cleanup null value at certain intervals
+ if (insertCounts.incrementAndGet() % CLEANUP_INTERVAL == 0) {
+ cleanNullValues()
+ }
+ super.+=(kv)
+ }
+
+ override def get(key: A): Option[B] = {
+ Option(internalJavaMap.get(key)) match {
+ case Some(weakValue) =>
+ val value = weakValue.weakValue.get
+ if (value == null) {
+ internalJavaMap.remove(key)
+ }
+ Option(value)
+ case None =>
+ None
+ }
--- End diff --
Not the same logic. This when value is null this makes the function return
Some(null) instead of None. Changing map to flatMap is the solution.
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