[SPARK-6077] Remove streaming tab while stopping StreamingContext

Currently we would create a new streaming tab for each streamingContext even if there's already one on the same sparkContext which would cause duplicate StreamingTab created and none of them is taking effect.
snapshot: https://www.dropbox.com/s/t4gd6hqyqo0nivz/bad%20multiple%20streamings.png?dl=0
How to reproduce:
1)
import org.apache.spark.SparkConf
import org.apache.spark.streaming.
{Seconds, StreamingContext}
import org.apache.spark.storage.StorageLevel
val ssc = new StreamingContext(sc, Seconds(1))
val lines = ssc.socketTextStream("localhost", 9999, StorageLevel.MEMORY_AND_DISK_SER)
val words = lines.flatMap(_.split(" "))
val wordCounts = words.map(x => (x, 1)).reduceByKey(_ + _)
wordCounts.print()
ssc.start()
.....
2)
ssc.stop(false)
val ssc = new StreamingContext(sc, Seconds(1))
val lines = ssc.socketTextStream("localhost", 9999, StorageLevel.MEMORY_AND_DISK_SER)
val words = lines.flatMap(_.split(" "))
val wordCounts = words.map(x => (x, 1)).reduceByKey(_ + _)
wordCounts.print()
ssc.start()

Author: lisurprise <zhichao.li@intel.com>

Closes #4828 from zhichao-li/master and squashes the following commits:

c329806 [lisurprise] add test for attaching/detaching streaming tab
51e6c7f [lisurprise] move detach method into StreamingTab
31a44fa [lisurprise] add unit test for attaching and detaching new tab
db25ed2 [lisurprise] clean code
8281bcb [lisurprise] clean code
193c542 [lisurprise] remove streaming tab while closing streaming context

3 files changed, 72 insertions, 44 deletions

diff --git a/core/src/main/scala/org/apache/spark/ui/WebUI.scala b/core/src/main/scala/org/apache/spark/ui/WebUI.scala
index ec68837a15..ea548f2312 100644
--- a/core/src/main/scala/org/apache/spark/ui/WebUI.scala
+++ b/core/src/main/scala/org/apache/spark/ui/WebUI.scala
@@ -20,14 +20,15 @@ package org.apache.spark.ui
 import javax.servlet.http.HttpServletRequest
 
 import scala.collection.mutable.ArrayBuffer
+import scala.collection.mutable.HashMap
 import scala.xml.Node
 
 import org.eclipse.jetty.servlet.ServletContextHandler
 import org.json4s.JsonAST.{JNothing, JValue}
 
-import org.apache.spark.{Logging, SecurityManager, SparkConf}
 import org.apache.spark.ui.JettyUtils._
 import org.apache.spark.util.Utils
+import org.apache.spark.{Logging, SecurityManager, SparkConf}
 
 /**
  * The top level component of the UI hierarchy that contains the server.
@@ -45,6 +46,7 @@ private[spark] abstract class WebUI(
 
   protected val tabs = ArrayBuffer[WebUITab]()
   protected val handlers = ArrayBuffer[ServletContextHandler]()
+  protected val pageToHandlers = new HashMap[WebUIPage, ArrayBuffer[ServletContextHandler]]
   protected var serverInfo: Option[ServerInfo] = None
   protected val localHostName = Utils.localHostName()
   protected val publicHostName = Option(conf.getenv("SPARK_PUBLIC_DNS")).getOrElse(localHostName)
@@ -60,14 +62,30 @@ private[spark] abstract class WebUI(
     tab.pages.foreach(attachPage)
     tabs += tab
   }
+  
+  def detachTab(tab: WebUITab) {
+    tab.pages.foreach(detachPage)
+    tabs -= tab
+  }
+  
+  def detachPage(page: WebUIPage) {
+    pageToHandlers.remove(page).foreach(_.foreach(detachHandler))
+  }
 
   /** Attach a page to this UI. */
   def attachPage(page: WebUIPage) {
     val pagePath = "/" + page.prefix
-    attachHandler(createServletHandler(pagePath,
-      (request: HttpServletRequest) => page.render(request), securityManager, basePath))
-    attachHandler(createServletHandler(pagePath.stripSuffix("/") + "/json",
-      (request: HttpServletRequest) => page.renderJson(request), securityManager, basePath))
+    val renderHandler = createServletHandler(pagePath,
+      (request: HttpServletRequest) => page.render(request), securityManager, basePath)
+    val renderJsonHandler = createServletHandler(pagePath.stripSuffix("/") + "/json",
+      (request: HttpServletRequest) => page.renderJson(request), securityManager, basePath)
+    attachHandler(renderHandler)
+    attachHandler(renderJsonHandler)
+    pageToHandlers.getOrElseUpdate(page, ArrayBuffer[ServletContextHandler]())
+      .append(renderHandler)
+    pageToHandlers.getOrElseUpdate(page, ArrayBuffer[ServletContextHandler]())
+      .append(renderJsonHandler)
+    
   }
 
   /** Attach a handler to this UI. */
diff --git a/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala b/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala
index 6a972381fa..0d155982a8 100644
--- a/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala
+++ b/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala
@@ -17,20 +17,24 @@
 
 package org.apache.spark.ui
 
+import javax.servlet.http.HttpServletRequest
+
 import scala.collection.JavaConversions._
+import scala.xml.Node
 
-import org.openqa.selenium.{By, WebDriver}
 import org.openqa.selenium.htmlunit.HtmlUnitDriver
+import org.openqa.selenium.{By, WebDriver}
 import org.scalatest._
 import org.scalatest.concurrent.Eventually._
 import org.scalatest.selenium.WebBrowser
 import org.scalatest.time.SpanSugar._
 
-import org.apache.spark._
 import org.apache.spark.LocalSparkContext._
+import org.apache.spark._
 import org.apache.spark.api.java.StorageLevels
 import org.apache.spark.shuffle.FetchFailedException
 
+
 /**
  * Selenium tests for the Spark Web UI.
  */
@@ -310,4 +314,46 @@ class UISeleniumSuite extends FunSuite with WebBrowser with Matchers with Before
       }
     }
   }
+
+  test("attaching and detaching a new tab") {
+    withSpark(newSparkContext()) { sc =>
+      val sparkUI = sc.ui.get
+
+      val newTab = new WebUITab(sparkUI, "foo") {
+        attachPage(new WebUIPage("") {
+          def render(request: HttpServletRequest): Seq[Node] = {
+            <b>"html magic"</b>
+          }
+        })
+      }
+      sparkUI.attachTab(newTab)
+      eventually(timeout(10 seconds), interval(50 milliseconds)) {
+        go to (sc.ui.get.appUIAddress.stripSuffix("/"))
+        find(cssSelector("""ul li a[href*="jobs"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="stages"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="storage"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="environment"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="foo"]""")) should not be(None)
+      }
+      eventually(timeout(10 seconds), interval(50 milliseconds)) {
+        // check whether new page exists
+        go to (sc.ui.get.appUIAddress.stripSuffix("/") + "/foo")
+        find(cssSelector("b")).get.text should include ("html magic")
+      }
+      sparkUI.detachTab(newTab)
+      eventually(timeout(10 seconds), interval(50 milliseconds)) {
+        go to (sc.ui.get.appUIAddress.stripSuffix("/"))
+        find(cssSelector("""ul li a[href*="jobs"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="stages"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="storage"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="environment"]""")) should not be(None)
+        find(cssSelector("""ul li a[href*="foo"]""")) should be(None)
+      }
+      eventually(timeout(10 seconds), interval(50 milliseconds)) {
+        // check new page not exist
+        go to (sc.ui.get.appUIAddress.stripSuffix("/") + "/foo")
+        find(cssSelector("b")) should be(None)
+      }
+    }
+  }
 }
diff --git a/core/src/test/scala/org/apache/spark/ui/UISuite.scala b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
index 92a21f82f3..77a038dc17 100644
--- a/core/src/test/scala/org/apache/spark/ui/UISuite.scala
+++ b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.ui
 
 import java.net.ServerSocket
-import javax.servlet.http.HttpServletRequest
 
 import scala.io.Source
 import scala.util.{Failure, Success, Try}
@@ -28,9 +27,8 @@ import org.scalatest.FunSuite
 import org.scalatest.concurrent.Eventually._
 import org.scalatest.time.SpanSugar._
 
-import org.apache.spark.{SparkContext, SparkConf}
 import org.apache.spark.LocalSparkContext._
-import scala.xml.Node
+import org.apache.spark.{SparkConf, SparkContext}
 
 class UISuite extends FunSuite {
 
@@ -72,40 +70,6 @@ class UISuite extends FunSuite {
     }
   }
 
-  ignore("attaching a new tab") {
-    withSpark(newSparkContext()) { sc =>
-      val sparkUI = sc.ui.get
-
-      val newTab = new WebUITab(sparkUI, "foo") {
-        attachPage(new WebUIPage("") {
-          def render(request: HttpServletRequest): Seq[Node] = {
-            <b>"html magic"</b>
-          }
-        })
-      }
-      sparkUI.attachTab(newTab)
-      eventually(timeout(10 seconds), interval(50 milliseconds)) {
-        val html = Source.fromURL(sparkUI.appUIAddress).mkString
-        assert(!html.contains("random data that should not be present"))
-
-        // check whether new page exists
-        assert(html.toLowerCase.contains("foo"))
-
-        // check whether other pages still exist
-        assert(html.toLowerCase.contains("stages"))
-        assert(html.toLowerCase.contains("storage"))
-        assert(html.toLowerCase.contains("environment"))
-        assert(html.toLowerCase.contains("executors"))
-      }
-
-      eventually(timeout(10 seconds), interval(50 milliseconds)) {
-        val html = Source.fromURL(sparkUI.appUIAddress.stripSuffix("/") + "/foo").mkString
-        // check whether new page exists
-        assert(html.contains("magic"))
-      }
-    }
-  }
-
   test("jetty selects different port under contention") {
     val server = new ServerSocket(0)
     val startPort = server.getLocalPort