Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/126#discussion_r10551528
--- Diff:
core/src/main/scala/org/apache/spark/util/TimeStampedWeakValueHashMap.scala ---
@@ -0,0 +1,112 @@
+/*
+ * 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
+
+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
--- End diff --
This is a case where we really should be using the
[ReferenceQueue](http://docs.oracle.com/javase/7/docs/api/java/lang/ref/ReferenceQueue.html)
cleanup mechanism.
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