Fix bug that applications status uncorrect on JobHistory UI.

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

@@ -19,6 +19,7 @@ package org.apache.spark.deploy.history
 
 import java.io.{BufferedInputStream, FileNotFoundException, InputStream, IOException, OutputStream}
 import java.util.concurrent.{ExecutorService, Executors, TimeUnit}
+import java.util.UUID
 import java.util.zip.{ZipEntry, ZipOutputStream}
 
 import scala.collection.mutable
@@ -73,7 +74,7 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
   // The modification time of the newest log detected during the last scan. This is used
   // to ignore logs that are older during subsequent scans, to avoid processing data that
   // is already known.
-  private var lastModifiedTime = -1L
+  private var lastScanTime = -1L
 
   // Mapping of application IDs to their metadata, in descending end time order. Apps are inserted
   // into the map in order, so the LinkedHashMap maintains the correct ordering.
@@ -179,15 +180,14 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
    */
   private[history] def checkForLogs(): Unit = {
     try {
+      val newLastScanTime = getNewLastScanTime()
       val statusList = Option(fs.listStatus(new Path(logDir))).map(_.toSeq)
         .getOrElse(Seq[FileStatus]())
-      var newLastModifiedTime = lastModifiedTime
       val logInfos: Seq[FileStatus] = statusList
         .filter { entry =>
           try {
             getModificationTime(entry).map { time =>
-              newLastModifiedTime = math.max(newLastModifiedTime, time)
-              time >= lastModifiedTime
+              time >= lastScanTime
             }.getOrElse(false)
           } catch {
             case e: AccessControlException =>
@@ -224,12 +224,29 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
           }
         }
 
-      lastModifiedTime = newLastModifiedTime
+      lastScanTime = newLastScanTime
     } catch {
       case e: Exception => logError("Exception in checking for event log updates", e)
     }
   }
 
+  private def getNewLastScanTime(): Long = {
+    val fileName = "." + UUID.randomUUID().toString
+    val path = new Path(logDir, fileName)
+    val fos = fs.create(path)
+
+    try {
+      fos.close()
+      fs.getFileStatus(path).getModificationTime
+    } catch {
+      case e: Exception =>
+        logError("Exception encountered when attempting to update last scan time", e)
+        lastScanTime
+    } finally {
+      fs.delete(path)
+    }
+  }
+
   override def writeEventLogs(
       appId: String,
       attemptId: Option[String],