Address Patrick's comments

core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala

@@ -32,7 +32,7 @@ import org.apache.spark.ui.JettyUtils._
 import org.apache.spark.util.Utils
 
 /**
- * A web server that renders SparkUIs of finished applications.
+ * A web server that renders SparkUIs of completed applications.
  *
  * For the standalone mode, MasterWebUI already achieves this functionality. Thus, the
  * main use case of the HistoryServer is in other deploy modes (e.g. Yarn or Mesos).
@@ -61,8 +61,8 @@ class HistoryServer(
   // A timestamp of when the disk was last accessed to check for log updates
   private var lastLogCheckTime = -1L
 
-  // Number of complete applications found in this directory
-  private var numApplicationsTotal = 0
+  // Number of completed applications found in this directory
+  private var numCompletedApplications = 0
 
   @volatile private var stopped = false
 
@@ -125,11 +125,11 @@ class HistoryServer(
    * Check for any updates to event logs in the base directory. This is only effective once
    * the server has been bound.
    *
-   * If a new finished application is found, the server renders the associated SparkUI
+   * If a new completed application is found, the server renders the associated SparkUI
    * from the application's event logs, attaches this UI to itself, and stores metadata
    * information for this application.
    *
-   * If the logs for an existing finished application are no longer found, the server
+   * If the logs for an existing completed application are no longer found, the server
    * removes all associated information and detaches the SparkUI.
    */
   def checkForLogs() = synchronized {
@@ -164,8 +164,8 @@ class HistoryServer(
           }
         }
 
-        // Track the total number of complete applications observed this round
-        numApplicationsTotal = logInfos.size
+        // Track the total number of completed applications observed this round
+        numCompletedApplications = logInfos.size
 
       } catch {
         case t: Throwable => logError("Exception in checking for event log updates", t)
@@ -176,10 +176,10 @@ class HistoryServer(
   }
 
   /**
-   * Render a new SparkUI from the event logs if the associated application is finished.
+   * Render a new SparkUI from the event logs if the associated application is completed.
    *
    * HistoryServer looks for a special file that indicates application completion in the given
-   * directory. If this file exists, the associated application is regarded to be complete, in
+   * directory. If this file exists, the associated application is regarded to be completed, in
    * which case the server proceeds to render the SparkUI. Otherwise, the server does nothing.
    */
   private def renderSparkUI(logDir: FileStatus, logInfo: EventLoggingInfo) {
@@ -200,7 +200,7 @@ class HistoryServer(
       val startTime = appListener.startTime
       val endTime = appListener.endTime
       val lastUpdated = getModificationTime(logDir)
-      ui.setAppName(appName + " (finished)")
+      ui.setAppName(appName + " (completed)")
       appIdToInfo(appId) = ApplicationHistoryInfo(appId, appName, startTime, endTime,
         lastUpdated, sparkUser, path, ui)
     }
@@ -216,14 +216,14 @@ class HistoryServer(
   /** Return the address of this server. */
   def getAddress: String = "http://" + publicHost + ":" + boundPort
 
-  /** Return the total number of application logs found, whether or not the UI is retained. */
-  def getNumApplications: Int = numApplicationsTotal
+  /** Return the number of completed applications found, whether or not the UI is rendered. */
+  def getNumApplications: Int = numCompletedApplications
 
   /** Return when this directory was last modified. */
   private def getModificationTime(dir: FileStatus): Long = {
     try {
       val logFiles = fileSystem.listStatus(dir.getPath)
-      if (logFiles != null) {
+      if (logFiles != null && !logFiles.isEmpty) {
         logFiles.map(_.getModificationTime).max
       } else {
         dir.getModificationTime
@@ -283,5 +283,5 @@ private[spark] case class ApplicationHistoryInfo(
     logDirPath: Path,
     ui: SparkUI) {
   def started = startTime != -1
-  def finished = endTime != -1
+  def completed = endTime != -1
 }

core/src/main/scala/org/apache/spark/deploy/history/HistoryServerArguments.scala

@@ -55,8 +55,12 @@ private[spark] class HistoryServerArguments(args: Array[String]) {
     }
     val fileSystem = Utils.getHadoopFileSystem(new URI(logDir))
     val path = new Path(logDir)
-    if (!fileSystem.exists(path) || !fileSystem.getFileStatus(path).isDir) {
-      System.err.println("Logging directory specified is invalid: %s".format(logDir))
+    if (!fileSystem.exists(path)) {
+      System.err.println("Logging directory specified does not exist: %s".format(logDir))
+      printUsageAndExit(1)
+    }
+    if (!fileSystem.getFileStatus(path).isDir) {
+      System.err.println("Logging directory specified is not a directory: %s".format(logDir))
       printUsageAndExit(1)
     }
   }

core/src/main/scala/org/apache/spark/deploy/history/IndexPage.scala

@@ -63,8 +63,8 @@ private[spark] class IndexPage(parent: HistoryServer) {
     val appName = if (info.started) info.name else info.logDirPath.getName
     val uiAddress = parent.getAddress + info.ui.basePath
     val startTime = if (info.started) WebUI.formatDate(info.startTime) else "Not started"
-    val endTime = if (info.finished) WebUI.formatDate(info.endTime) else "Not finished"
-    val difference = if (info.started && info.finished) info.endTime - info.startTime else -1L
+    val endTime = if (info.completed) WebUI.formatDate(info.endTime) else "Not finished"
+    val difference = if (info.started && info.completed) info.endTime - info.startTime else -1L
     val duration = if (difference > 0) WebUI.formatDuration(difference) else "---"
     val sparkUser = if (info.started) info.sparkUser else "Unknown user"
     val logDirectory = info.logDirPath.getName

core/src/main/scala/org/apache/spark/deploy/master/Master.scala

@@ -667,7 +667,7 @@ private[spark] class Master(
     if (!eventLogPaths.isEmpty) {
       try {
         val replayBus = new ReplayListenerBus(eventLogPaths, fileSystem, compressionCodec)
-        val ui = new SparkUI(replayBus, appName + " (finished)", "/history/" + app.id)
+        val ui = new SparkUI(replayBus, appName + " (completed)", "/history/" + app.id)
         ui.start()
         replayBus.replay()
         app.desc.appUiUrl = ui.basePath

core/src/main/scala/org/apache/spark/scheduler/ApplicationEventListener.scala

@@ -20,9 +20,8 @@ package org.apache.spark.scheduler
 /**
  * A simple listener for application events.
  *
- * This listener assumes at most one of each of SparkListenerApplicationStart and
- * SparkListenerApplicationEnd will be received. Otherwise, only the latest event
- * of each type will take effect.
+ * This listener expects to hear events from a single application only. If events
+ * from multiple applications are seen, the behavior is unspecified.
  */
 private[spark] class ApplicationEventListener extends SparkListener {
   var appName = "<Not Started>"

core/src/main/scala/org/apache/spark/scheduler/EventLoggingListener.scala

@@ -17,6 +17,8 @@
 
 package org.apache.spark.scheduler
 
+import scala.collection.mutable
+
 import org.apache.hadoop.fs.{FileSystem, Path}
 import org.json4s.jackson.JsonMethods._
 
@@ -118,6 +120,9 @@ private[spark] object EventLoggingListener extends Logging {
   val COMPRESSION_CODEC_PREFIX = "COMPRESSION_CODEC_"
   val APPLICATION_COMPLETE = "APPLICATION_COMPLETE"
 
+  // A cache for compression codecs to avoid creating the same codec many times
+  private val codecMap = new mutable.HashMap[String, CompressionCodec]
+
   def isEventLogFile(fileName: String): Boolean = {
     fileName.startsWith(LOG_PREFIX)
   }
@@ -174,11 +179,11 @@ private[spark] object EventLoggingListener extends Logging {
         compressionCodec = filePaths
           .find { path => isCompressionCodecFile(path.getName) }
           .map { path =>
-          val codec = EventLoggingListener.parseCompressionCodec(path.getName)
-          val conf = new SparkConf
-          conf.set("spark.io.compression.codec", codec)
-          CompressionCodec.createCodec(conf)
-        },
+            val codec = EventLoggingListener.parseCompressionCodec(path.getName)
+            val conf = new SparkConf
+            conf.set("spark.io.compression.codec", codec)
+            codecMap.getOrElseUpdate(codec, CompressionCodec.createCodec(conf))
+          },
         applicationComplete = filePaths.exists { path => isApplicationCompleteFile(path.getName) }
       )
     } catch {