Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/126#discussion_r10553150
--- Diff: core/src/main/scala/org/apache/spark/util/BoundedHashMap.scala ---
@@ -0,0 +1,67 @@
+/*
+ * 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.mutable.{ArrayBuffer, SynchronizedMap}
+
+import java.util.{Collections, LinkedHashMap}
+import java.util.Map.{Entry => JMapEntry}
+import scala.reflect.ClassTag
+
+/**
+ * A map that upper bounds the number of key-value pairs present in it. It
can be configured to
+ * drop the least recently user pair or the earliest inserted pair. It
exposes a
+ * scala.collection.mutable.Map interface to allow it to be a drop-in
replacement for Scala
+ * HashMaps.
+ *
+ * Internally, a Java LinkedHashMap is used to get insert-order or
access-order behavior.
+ * Note that the LinkedHashMap is not thread-safe and hence, it is wrapped
in a
+ * Collections.synchronizedMap. However, getting the Java HashMap's
iterator and
+ * using it can still lead to ConcurrentModificationExceptions. Hence, the
iterator()
+ * function is overridden to copy the all pairs into an ArrayBuffer and
then return the
+ * iterator to the ArrayBuffer. Also, the class apply the trait
SynchronizedMap which
+ * ensures that all calls to the Scala Map API are synchronized. This
together ensures
+ * that ConcurrentModificationException is never thrown.
+ *
+ * @param bound max number of key-value pairs
+ * @param useLRU true = least recently used/accessed will be dropped when
bound is reached,
+ * false = earliest inserted will be dropped
+ */
+private[spark] class BoundedHashMap[A, B](bound: Int, useLRU: Boolean)
+ extends WrappedJavaHashMap[A, B, A, B] with SynchronizedMap[A, B] {
+
+ protected[util] val internalJavaMap = Collections.synchronizedMap(new
LinkedHashMap[A, B](
+ bound / 8, (0.75).toFloat, useLRU) {
+ override protected def removeEldestEntry(eldest: JMapEntry[A, B]):
Boolean = {
+ size() > bound
+ }
+ })
+
+ protected[util] def newInstance[K1, V1](): WrappedJavaHashMap[K1, V1, _,
_] = {
--- End diff --
Oopsie. I thought them to be public. Seems like I didnt.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
