[SPARK-29477] Improve tooltip for Streaming tab

### What changes were proposed in this pull request?
Added tooltip for duration columns in the batch table of streaming tab of Web UI.

### Why are the changes needed?
Tooltips will help users in understanding columns of batch table of streaming tab.

### Does this PR introduce any user-facing change?
Yes

### How was this patch tested?
Manually tested.

Closes apache#26467 from iRakson/streaming_tab_tooltip.

Authored-by: root1 <[email protected]>
Signed-off-by: Sean Owen <[email protected]>

Author: iRakson

streaming/src/main/scala/org/apache/spark/streaming/ui/BatchPage.scala

@@ -37,10 +37,13 @@ private[ui] class BatchPage(parent: StreamingTab) extends WebUIPage("batch") {
   private def columns: Seq[Node] = {
     <th>Output Op Id</th>
       <th>Description</th>
-      <th>Output Op Duration</th>
+      <th>Output Op Duration {SparkUIUtils.tooltip("Time taken for all the jobs of this batch to" +
+        " finish processing from the time they were submitted.",
+        "top")}</th>
       <th>Status</th>
       <th>Job Id</th>
-      <th>Job Duration</th>
+      <th>Job Duration {SparkUIUtils.tooltip("Time taken from submission time to completion " +
+        "time of the job", "top")}</th>
       <th class="sorttable_nosort">Stages: Succeeded/Total</th>
       <th class="sorttable_nosort">Tasks (for all stages): Succeeded/Total</th>
       <th>Error</th>
@@ -381,7 +384,7 @@ private[ui] class BatchPage(parent: StreamingTab) extends WebUIPage("batch") {
       <thead>
         <tr>
           <th>Input</th>
-          <th>Metadata</th>
+          <th>Metadata {SparkUIUtils.tooltip("Batch Input Details", "right")}</th>
         </tr>
       </thead>
       <tbody>

streaming/src/test/scala/org/apache/spark/streaming/UISeleniumSuite.scala

@@ -151,8 +151,9 @@ class UISeleniumSuite
         summaryText should contain ("Total delay:")
 
         findAll(cssSelector("""#batch-job-table th""")).map(_.text).toSeq should be {
-          List("Output Op Id", "Description", "Output Op Duration", "Status", "Job Id",
-            "Job Duration", "Stages: Succeeded/Total", "Tasks (for all stages): Succeeded/Total",
+          List("Output Op Id", "Description", "Output Op Duration (?)", "Status", "Job Id",
+            "Job Duration (?)", "Stages: Succeeded/Total",
+            "Tasks (for all stages): Succeeded/Total",
             "Error")
         }
 
@@ -163,7 +164,7 @@ class UISeleniumSuite
 
         // Check job ids
         val jobIdCells = findAll(cssSelector( """#batch-job-table a""")).toSeq
-        jobIdCells.map(_.text) should be (List("0", "1", "2", "3"))
+        jobIdCells.map(_.text).filter(_.forall(_.isDigit)) should be (List("0", "1", "2", "3"))
 
         val jobLinks = jobIdCells.flatMap(_.attribute("href"))
         jobLinks.size should be (4)