SPARK-25973 Spark History Main page performance improvement (apache#81)

SPARK-25973 Spark History Main page performance improvement

Author: Willymontaz

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

@@ -31,8 +31,8 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
     val requestedIncomplete =
       Option(UIUtils.stripXSS(request.getParameter("showIncomplete"))).getOrElse("false").toBoolean
 
-    val allAppsSize = parent.getApplicationList()
-      .count(isApplicationCompleted(_) != requestedIncomplete)
+    val displayApplications = parent.getApplicationList()
+      .exists(isApplicationCompleted(_) != requestedIncomplete)
     val eventLogsUnderProcessCount = parent.getEventLogsUnderProcess()
     val lastUpdatedTime = parent.getLastUpdatedTime()
     val providerConfig = parent.getProviderConfig()
@@ -63,7 +63,7 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
             }
 
             {
-            if (allAppsSize > 0) {
+            if (displayApplications) {
               <script src={UIUtils.prependBaseUri("/static/dataTables.rowsGroup.js")}></script> ++
                 <div id="history-summary" class="row-fluid"></div> ++
                 <script src={UIUtils.prependBaseUri("/static/historypage.js")}></script> ++