Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/1608#discussion_r15438461
--- Diff:
external/hbase/src/main/scala/org/apache/spark/hbase/HConnectionStaticCache.scala
---
@@ -0,0 +1,141 @@
+/*
+ * 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.hbase
+
+import java.util.HashMap
+import org.apache.hadoop.hbase.client.HConnection
+import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.atomic.AtomicLong
+import java.util.Timer
+import org.apache.hadoop.conf.Configuration
+import org.apache.hadoop.hbase.HConstants
+import org.apache.hadoop.hbase.client.HConnectionManager
+import java.util.TimerTask
+import scala.collection.mutable.MutableList
+import org.apache.spark.Logging
+
+/**
+ * A static caching class that will manage all HConnection in a worker
+ *
+ * The main idea is there is a hashMap with
+ * HConstants.HBASE_CLIENT_INSTANCE_ID which is
("hbase.client.instance.id")
+ *
+ * In that HashMap there is three things
+ * - HConnection
+ * - Number of checked out users of the HConnection
+ * - Time since the HConnection was last used
+ *
+ * There is also a Timer thread that will start up every 2 minutes
+ * When the Timer thread starts up it will look for HConnection with no
+ * checked out users and a last used time that is older then 1 minute.
+ *
+ * This class is not intended to be used by Users
+ */
+object HConnectionStaticCache extends Logging{
+ @transient private val hconnectionMap =
+ new HashMap[String, (HConnection, AtomicInteger, AtomicLong)]
--- End diff --
This is using a lot of the Java collection API instead of Scala API. I
think the latter would be more standard. In fact, it would help in a number of
cases, like the one in the next comment.
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