[SPARK-21809] : Made changes as per comments

Reverted the function getStandAloneAppId() to take in function as parameter, removing unused variable taskTableHtml in StagePage.scala and adding additional check for displaying accumulator column in task table

Author: pgandhi

core/src/main/resources/org/apache/spark/ui/static/executorspage.js

@@ -126,10 +126,7 @@ $(document).ready(function () {
 
     executorsSummary = $("#active-executors");
 
-    var app_id = getStandAloneAppId();
-    buildExecutorDataTables(app_id);
-
-    function buildExecutorDataTables(appId) {
+    getStandAloneAppId(function (appId) {
 
         var endPoint = createRESTEndPoint(appId);
         $.getJSON(endPoint, function (response, status, jqXHR) {
@@ -548,5 +545,5 @@ $(document).ready(function () {
 
             });
         });
-    }
+    });
 });

core/src/main/resources/org/apache/spark/ui/static/stagepage.js

@@ -36,7 +36,7 @@ $.extend( $.fn.dataTable.ext.type.order, {
     }
 } );
 
-// This function will only parse the URL under certain formate
+// This function will only parse the URL under certain format
 // e.g. https://axonitered-jt1.red.ygrid.yahoo.com:50509/history/application_1502220952225_59143/stages/stage/?id=0&attempt=0
 function stageEndPoint(appId) {
     var words = document.baseURI.split('/');
@@ -103,10 +103,7 @@ $(document).ready(function () {
         "</div>");
 
     tasksSummary = $("#active-tasks");
-    var app_id = getStandAloneAppId();
-    buildStageDataTables(app_id);
-
-    function buildStageDataTables(appId) {
+    getStandAloneAppId(function (appId) {
 
         var endPoint = stageEndPoint(appId);
         $.getJSON(endPoint, function(response, status, jqXHR) {
@@ -386,7 +383,7 @@ $(document).ready(function () {
                         },
                         {
                             data : function (row, type) {
-                                if (accumulator_table.length > 0) {
+                                if (accumulator_table.length > 0 && row.accumulatorUpdates.length > 0) {
                                     return row.accumulatorUpdates[0].name + ' : ' + row.accumulatorUpdates[0].update;
                                 } else {
                                     return 0;
@@ -467,5 +464,5 @@ $(document).ready(function () {
                 }
             });
         });
-    }
+    });
 });

core/src/main/resources/org/apache/spark/ui/static/utils.js

@@ -57,24 +57,27 @@ function formatLogsCells(execLogs, type) {
     return result;
 }
 
-function getStandAloneAppId() {
+function getStandAloneAppId(cb) {
     var words = document.baseURI.split('/');
     var ind = words.indexOf("proxy");
     if (ind > 0) {
         var appId = words[ind + 1];
-        return appId;
+        cb(appId);
+        return;
     }
     ind = words.indexOf("history");
     if (ind > 0) {
         var appId = words[ind + 1];
-        return appId;
+        cb(appId);
+        return;
     }
     //Looks like Web UI is running in standalone mode
     //Let's get application-id using REST End Point
     $.getJSON(location.origin + "/api/v1/applications", function(response, status, jqXHR) {
         if (response && response.length > 0) {
-            var appId = response[0].id
-            return appId;
+            var appId = response[0].id;
+            cb(appId);
+            return;
         }
     });
 }

core/src/main/scala/org/apache/spark/ui/jobs/StagePage.scala

@@ -206,7 +206,7 @@ private[ui] class StagePage(parent: StagesTab) extends WebUIPage("stage") {
         }
       }
       val currentTime = System.currentTimeMillis()
-      val (taskTable, taskTableHTML) = try {
+      val taskTable = try {
         val _taskTable = new TaskPagedTable(
           parent.conf,
           UIUtils.prependBaseUri(parent.basePath) +
@@ -225,17 +225,11 @@ private[ui] class StagePage(parent: StagesTab) extends WebUIPage("stage") {
           desc = taskSortDesc,
           executorsListener = executorsListener
         )
-        (_taskTable, _taskTable.table(page))
+        _taskTable.table(page)
+        _taskTable
       } catch {
         case e @ (_ : IllegalArgumentException | _ : IndexOutOfBoundsException) =>
-          val errorMessage =
-            <div class="alert alert-error">
-              <p>Error while rendering stage table:</p>
-              <pre>
-                {Utils.exceptionString(e)}
-              </pre>
-            </div>
-          (null, errorMessage)
+          null
       }
 
       val jsForScrollingDownToTaskTable =