[SPARK-15083][WEB UI] History Server can OOM due to unlimited TaskUIData

## What changes were proposed in this pull request?

Based on #12990 by tankkyo

Since the History Server currently loads all application's data it can OOM if too many applications have a significant task count. `spark.ui.trimTasks` (default: false) can be set to true to trim tasks by `spark.ui.retainedTasks` (default: 10000)

(This is a "quick fix" to help those running into the problem until a update of how the history server loads app data can be done)

## How was this patch tested?

Manual testing and dev/run-tests

![spark-15083](https://cloud.githubusercontent.com/assets/13952758/17713694/fe82d246-63b0-11e6-9697-b87ea75ff4ef.png)

Author: Alex Bozarth <ajbozart@us.ibm.com>

Closes #14673 from ajbozarth/spark15083.

8 files changed, 248 insertions, 228 deletions

diff --git a/core/src/main/scala/org/apache/spark/internal/config/package.scala b/core/src/main/scala/org/apache/spark/internal/config/package.scala
index be3dac4d24..47174e4efe 100644
--- a/core/src/main/scala/org/apache/spark/internal/config/package.scala
+++ b/core/src/main/scala/org/apache/spark/internal/config/package.scala
@@ -114,4 +114,9 @@ package object config {
   private[spark] val PYSPARK_PYTHON = ConfigBuilder("spark.pyspark.python")
     .stringConf
     .createOptional
+
+  // To limit memory usage, we only track information for a fixed number of tasks
+  private[spark] val UI_RETAINED_TASKS = ConfigBuilder("spark.ui.retainedTasks")
+    .intConf
+    .createWithDefault(100000)
 }
diff --git a/core/src/main/scala/org/apache/spark/ui/jobs/JobProgressListener.scala b/core/src/main/scala/org/apache/spark/ui/jobs/JobProgressListener.scala
index 491f7160bc..d3a4f9d322 100644
--- a/core/src/main/scala/org/apache/spark/ui/jobs/JobProgressListener.scala
+++ b/core/src/main/scala/org/apache/spark/ui/jobs/JobProgressListener.scala
@@ -19,12 +19,13 @@ package org.apache.spark.ui.jobs
 
 import java.util.concurrent.TimeoutException
 
-import scala.collection.mutable.{HashMap, HashSet, ListBuffer}
+import scala.collection.mutable.{HashMap, HashSet, LinkedHashMap, ListBuffer}
 
 import org.apache.spark._
 import org.apache.spark.annotation.DeveloperApi
 import org.apache.spark.executor.TaskMetrics
 import org.apache.spark.internal.Logging
+import org.apache.spark.internal.config._
 import org.apache.spark.scheduler._
 import org.apache.spark.scheduler.SchedulingMode.SchedulingMode
 import org.apache.spark.storage.BlockManagerId
@@ -93,6 +94,7 @@ class JobProgressListener(conf: SparkConf) extends SparkListener with Logging {
 
   val retainedStages = conf.getInt("spark.ui.retainedStages", SparkUI.DEFAULT_RETAINED_STAGES)
   val retainedJobs = conf.getInt("spark.ui.retainedJobs", SparkUI.DEFAULT_RETAINED_JOBS)
+  val retainedTasks = conf.get(UI_RETAINED_TASKS)
 
   // We can test for memory leaks by ensuring that collections that track non-active jobs and
   // stages do not grow without bound and that collections for active jobs/stages eventually become
@@ -405,6 +407,11 @@ class JobProgressListener(conf: SparkConf) extends SparkListener with Logging {
       taskData.updateTaskMetrics(taskMetrics)
       taskData.errorMessage = errorMessage
 
+      // If Tasks is too large, remove and garbage collect old tasks
+      if (stageData.taskData.size > retainedTasks) {
+        stageData.taskData = stageData.taskData.drop(stageData.taskData.size - retainedTasks)
+      }
+
       for (
         activeJobsDependentOnStage <- stageIdToActiveJobIds.get(taskEnd.stageId);
         jobId <- activeJobsDependentOnStage;
diff --git a/core/src/main/scala/org/apache/spark/ui/jobs/StagePage.scala b/core/src/main/scala/org/apache/spark/ui/jobs/StagePage.scala
index ea7acc4734..a266164587 100644
--- a/core/src/main/scala/org/apache/spark/ui/jobs/StagePage.scala
+++ b/core/src/main/scala/org/apache/spark/ui/jobs/StagePage.scala
@@ -133,7 +133,14 @@ private[ui] class StagePage(parent: StagesTab) extends WebUIPage("stage") {
 
       val stageData = stageDataOption.get
       val tasks = stageData.taskData.values.toSeq.sortBy(_.taskInfo.launchTime)
-      val numCompleted = tasks.count(_.taskInfo.finished)
+      val numCompleted = stageData.numCompleteTasks
+      val totalTasks = stageData.numActiveTasks +
+        stageData.numCompleteTasks + stageData.numFailedTasks
+      val totalTasksNumStr = if (totalTasks == tasks.size) {
+        s"$totalTasks"
+      } else {
+        s"$totalTasks, showing ${tasks.size}"
+      }
 
       val allAccumulables = progressListener.stageIdToData((stageId, stageAttemptId)).accumulables
       val externalAccumulables = allAccumulables.values.filter { acc => !acc.internal }
@@ -591,7 +598,8 @@ private[ui] class StagePage(parent: StagesTab) extends WebUIPage("stage") {
         <div>{summaryTable.getOrElse("No tasks have reported metrics yet.")}</div> ++
         aggMetrics ++
         maybeAccumulableTable ++
-        <h4 id="tasks-section">Tasks</h4> ++ taskTableHTML ++ jsForScrollingDownToTaskTable
+        <h4 id="tasks-section">Tasks ({totalTasksNumStr})</h4> ++
+          taskTableHTML ++ jsForScrollingDownToTaskTable
       UIUtils.headerSparkPage(stageHeader, content, parent, showVisualization = true)
     }
   }
diff --git a/core/src/main/scala/org/apache/spark/ui/jobs/UIData.scala b/core/src/main/scala/org/apache/spark/ui/jobs/UIData.scala
index 20dde7cec8..66b88129ee 100644
--- a/core/src/main/scala/org/apache/spark/ui/jobs/UIData.scala
+++ b/core/src/main/scala/org/apache/spark/ui/jobs/UIData.scala
@@ -18,7 +18,7 @@
 package org.apache.spark.ui.jobs
 
 import scala.collection.mutable
-import scala.collection.mutable.HashMap
+import scala.collection.mutable.{HashMap, LinkedHashMap}
 
 import org.apache.spark.JobExecutionStatus
 import org.apache.spark.executor.{ShuffleReadMetrics, ShuffleWriteMetrics, TaskMetrics}
@@ -97,7 +97,7 @@ private[spark] object UIData {
     var description: Option[String] = None
 
     var accumulables = new HashMap[Long, AccumulableInfo]
-    var taskData = new HashMap[Long, TaskUIData]
+    var taskData = new LinkedHashMap[Long, TaskUIData]
     var executorSummary = new HashMap[String, ExecutorSummary]
 
     def hasInput: Boolean = inputBytes > 0
diff --git a/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_expectation.json b/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_expectation.json
index 11eec0b49c..96d86b7278 100644
--- a/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_expectation.json
+++ b/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_expectation.json
@@ -39,21 +39,21 @@
     }
   }
 }, {
-  "taskId" : 5,
-  "index" : 5,
+  "taskId" : 1,
+  "index" : 1,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.505GMT",
+  "launchTime" : "2015-05-06T13:03:06.502GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 30,
+    "executorDeserializeTime" : 31,
     "executorRunTime" : 350,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 1,
+    "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -74,26 +74,26 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 3675510,
+      "writeTime" : 3934399,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 1,
-  "index" : 1,
+  "taskId" : 5,
+  "index" : 5,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.502GMT",
+  "launchTime" : "2015-05-06T13:03:06.505GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 31,
+    "executorDeserializeTime" : 30,
     "executorRunTime" : 350,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 0,
+    "resultSerializationTime" : 1,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -114,22 +114,22 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 3934399,
+      "writeTime" : 3675510,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 4,
-  "index" : 4,
+  "taskId" : 0,
+  "index" : 0,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.504GMT",
+  "launchTime" : "2015-05-06T13:03:06.494GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 31,
+    "executorDeserializeTime" : 32,
     "executorRunTime" : 349,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
@@ -137,7 +137,7 @@
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
-      "bytesRead" : 60488,
+      "bytesRead" : 49294,
       "recordsRead" : 10000
     },
     "outputMetrics" : {
@@ -154,15 +154,15 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 83022,
+      "writeTime" : 3842811,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 7,
-  "index" : 7,
+  "taskId" : 3,
+  "index" : 3,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.506GMT",
+  "launchTime" : "2015-05-06T13:03:06.504GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
@@ -173,7 +173,7 @@
     "executorRunTime" : 349,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 0,
+    "resultSerializationTime" : 2,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -194,13 +194,13 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 2579051,
+      "writeTime" : 1311694,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 3,
-  "index" : 3,
+  "taskId" : 4,
+  "index" : 4,
   "attempt" : 0,
   "launchTime" : "2015-05-06T13:03:06.504GMT",
   "executorId" : "driver",
@@ -213,7 +213,7 @@
     "executorRunTime" : 349,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 2,
+    "resultSerializationTime" : 1,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -234,30 +234,30 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 1311694,
+      "writeTime" : 83022,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 0,
-  "index" : 0,
+  "taskId" : 7,
+  "index" : 7,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.494GMT",
+  "launchTime" : "2015-05-06T13:03:06.506GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 32,
+    "executorDeserializeTime" : 31,
     "executorRunTime" : 349,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 1,
+    "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
-      "bytesRead" : 49294,
+      "bytesRead" : 60488,
       "recordsRead" : 10000
     },
     "outputMetrics" : {
@@ -274,7 +274,7 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 3842811,
+      "writeTime" : 2579051,
       "recordsWritten" : 10
     }
   }
@@ -479,25 +479,25 @@
     }
   }
 }, {
-  "taskId" : 16,
-  "index" : 16,
+  "taskId" : 9,
+  "index" : 9,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:07.001GMT",
+  "launchTime" : "2015-05-06T13:03:06.915GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 10,
+    "executorDeserializeTime" : 9,
     "executorRunTime" : 84,
     "resultSize" : 2010,
-    "jvmGcTime" : 5,
+    "jvmGcTime" : 0,
     "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
-      "bytesRead" : 70564,
+      "bytesRead" : 60489,
       "recordsRead" : 10000
     },
     "outputMetrics" : {
@@ -514,22 +514,22 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 108320,
+      "writeTime" : 101664,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 19,
-  "index" : 19,
+  "taskId" : 16,
+  "index" : 16,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:07.012GMT",
+  "launchTime" : "2015-05-06T13:03:07.001GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 5,
+    "executorDeserializeTime" : 10,
     "executorRunTime" : 84,
     "resultSize" : 2010,
     "jvmGcTime" : 5,
@@ -554,30 +554,30 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 95788,
+      "writeTime" : 108320,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 9,
-  "index" : 9,
+  "taskId" : 19,
+  "index" : 19,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.915GMT",
+  "launchTime" : "2015-05-06T13:03:07.012GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 9,
+    "executorDeserializeTime" : 5,
     "executorRunTime" : 84,
     "resultSize" : 2010,
-    "jvmGcTime" : 0,
+    "jvmGcTime" : 5,
     "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
-      "bytesRead" : 60489,
+      "bytesRead" : 70564,
       "recordsRead" : 10000
     },
     "outputMetrics" : {
@@ -594,25 +594,25 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 101664,
+      "writeTime" : 95788,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 20,
-  "index" : 20,
+  "taskId" : 14,
+  "index" : 14,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:07.014GMT",
+  "launchTime" : "2015-05-06T13:03:06.925GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 3,
+    "executorDeserializeTime" : 6,
     "executorRunTime" : 83,
     "resultSize" : 2010,
-    "jvmGcTime" : 5,
+    "jvmGcTime" : 0,
     "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
@@ -634,25 +634,25 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 97716,
+      "writeTime" : 95646,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 14,
-  "index" : 14,
+  "taskId" : 20,
+  "index" : 20,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.925GMT",
+  "launchTime" : "2015-05-06T13:03:07.014GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 6,
+    "executorDeserializeTime" : 3,
     "executorRunTime" : 83,
     "resultSize" : 2010,
-    "jvmGcTime" : 0,
+    "jvmGcTime" : 5,
     "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
@@ -674,7 +674,7 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 95646,
+      "writeTime" : 97716,
       "recordsWritten" : 10
     }
   }
diff --git a/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names___runtime_expectation.json b/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names___runtime_expectation.json
index 11eec0b49c..96d86b7278 100644
--- a/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names___runtime_expectation.json
+++ b/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names___runtime_expectation.json
@@ -39,21 +39,21 @@
     }
   }
 }, {
-  "taskId" : 5,
-  "index" : 5,
+  "taskId" : 1,
+  "index" : 1,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.505GMT",
+  "launchTime" : "2015-05-06T13:03:06.502GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 30,
+    "executorDeserializeTime" : 31,
     "executorRunTime" : 350,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 1,
+    "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -74,26 +74,26 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 3675510,
+      "writeTime" : 3934399,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 1,
-  "index" : 1,
+  "taskId" : 5,
+  "index" : 5,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.502GMT",
+  "launchTime" : "2015-05-06T13:03:06.505GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 31,
+    "executorDeserializeTime" : 30,
     "executorRunTime" : 350,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 0,
+    "resultSerializationTime" : 1,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -114,22 +114,22 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 3934399,
+      "writeTime" : 3675510,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 4,
-  "index" : 4,
+  "taskId" : 0,
+  "index" : 0,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.504GMT",
+  "launchTime" : "2015-05-06T13:03:06.494GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 31,
+    "executorDeserializeTime" : 32,
     "executorRunTime" : 349,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
@@ -137,7 +137,7 @@
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
-      "bytesRead" : 60488,
+      "bytesRead" : 49294,
       "recordsRead" : 10000
     },
     "outputMetrics" : {
@@ -154,15 +154,15 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 83022,
+      "writeTime" : 3842811,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 7,
-  "index" : 7,
+  "taskId" : 3,
+  "index" : 3,
   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:06.506GMT",
+  "launchTime" : "2015-05-06T13:03:06.504GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
@@ -173,7 +173,7 @@
     "executorRunTime" : 349,
     "resultSize" : 2010,
     "jvmGcTime" : 7,
-    "resultSerializationTime" : 0,
+    "resultSerializationTime" : 2,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
     "inputMetrics" : {
@@ -194,13 +194,13 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 2579051,
+      "writeTime" : 1311694,
       "recordsWritten" : 10
     }
   }
 }, {
-  "taskId" : 3,
-  "index" : 3,
+  "taskId" : 4,
+  "index" : 4,
   "attempt" : 0,
   "launchTime" : "2015-05-06T13:03:06.504GMT",
   "executorId" : "driver",
@@ -213,7 +213,7 @@
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diff --git a/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names__runtime_expectation.json b/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names__runtime_expectation.json
index 9528d872ef..e0e9e8140c 100644
--- a/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names__runtime_expectation.json
+++ b/core/src/test/resources/HistoryServerExpectations/stage_task_list_w__sortBy_short_names__runtime_expectation.json
@@ -39,21 +39,21 @@
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   "attempt" : 0,
-  "launchTime" : "2015-05-06T13:03:07.341GMT",
+  "launchTime" : "2015-05-06T13:03:07.243GMT",
   "executorId" : "driver",
   "host" : "localhost",
   "taskLocality" : "PROCESS_LOCAL",
   "speculative" : false,
   "accumulatorUpdates" : [ ],
   "taskMetrics" : {
-    "executorDeserializeTime" : 13,
+    "executorDeserializeTime" : 5,
     "executorRunTime" : 18,
     "resultSize" : 2065,
-    "jvmGcTime" : 5,
+    "jvmGcTime" : 0,
     "resultSerializationTime" : 0,
     "memoryBytesSpilled" : 0,
     "diskBytesSpilled" : 0,
@@ -794,7 +794,7 @@
     },
     "shuffleWriteMetrics" : {
       "bytesWritten" : 1710,
-      "writeTime" : 98069,
+      "writeTime" : 89664,
       "recordsWritten" : 10
     }
   }
diff --git a/core/src/test/scala/org/apache/spark/status/api/v1/AllStagesResourceSuite.scala b/core/src/test/scala/org/apache/spark/status/api/v1/AllStagesResourceSuite.scala
index f684e16c25..1bfb0c1547 100644
--- a/core/src/test/scala/org/apache/spark/status/api/v1/AllStagesResourceSuite.scala
+++ b/core/src/test/scala/org/apache/spark/status/api/v1/AllStagesResourceSuite.scala
@@ -19,7 +19,7 @@ package org.apache.spark.status.api.v1
 
 import java.util.Date
 
-import scala.collection.mutable.HashMap
+import scala.collection.mutable.LinkedHashMap
 
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.scheduler.{StageInfo, TaskInfo, TaskLocality}
@@ -28,7 +28,7 @@ import org.apache.spark.ui.jobs.UIData.{StageUIData, TaskUIData}
 class AllStagesResourceSuite extends SparkFunSuite {
 
   def getFirstTaskLaunchTime(taskLaunchTimes: Seq[Long]): Option[Date] = {
-    val tasks = new HashMap[Long, TaskUIData]
+    val tasks = new LinkedHashMap[Long, TaskUIData]
     taskLaunchTimes.zipWithIndex.foreach { case (time, idx) =>
       tasks(idx.toLong) = TaskUIData(
         new TaskInfo(idx, idx, 1, time, "", "", TaskLocality.ANY, false), None)