Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/718#discussion_r13365793
--- Diff:
core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala ---
@@ -0,0 +1,203 @@
+/*
+ * 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.deploy.history
+
+import java.io.FileNotFoundException
+import java.util.concurrent.atomic.AtomicReference
+
+import scala.collection.mutable
+
+import org.apache.hadoop.fs.{FileStatus, Path}
+
+import org.apache.spark.{Logging, SecurityManager, SparkConf}
+import org.apache.spark.scheduler._
+import org.apache.spark.ui.SparkUI
+import org.apache.spark.util.Utils
+
+private[history] class FsHistoryProvider(conf: SparkConf) extends
ApplicationHistoryProvider
+ with Logging {
+
+ // Interval between each check for event log updates
+ private val UPDATE_INTERVAL_MS =
conf.getInt("spark.history.fs.updateInterval", 10) * 1000
+
+ private val logDir = conf.get("spark.history.fs.logDirectory")
+ private val fs = Utils.getHadoopFileSystem(logDir)
+
+ // A timestamp of when the disk was last accessed to check for log
updates
+ private var lastLogCheckTimeMs = -1L
+
+ // List of applications, in order from newest to oldest.
+ private val appList = new
AtomicReference[Seq[ApplicationHistoryInfo]](Nil)
--- End diff --
Is there a reason not to just use an `ArrayBuffer` here and add some
synchronization around resetting and reading it? This `AtomicReference` thing
is a little bit clunky and I don't see any performance argument for it.
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