[SPARK-11338] [WEBUI] Prepend app links on HistoryPage with uiRoot path

[SPARK-11338: HistoryPage not multi-tenancy enabled ...](https://issues.apache.org/jira/browse/SPARK-11338)
- `HistoryPage.scala` ...prepending all page links with the web proxy (`uiRoot`) path
- `HistoryServerSuite.scala` ...adding a test case to verify all site-relative links are prefixed when the environment variable `APPLICATION_WEB_PROXY_BASE` (or System property `spark.ui.proxyBase`) is set

Author: Christian Kadner <ckadner@us.ibm.com>

Closes #9291 from ckadner/SPARK-11338 and squashes the following commits:

01d2f35 [Christian Kadner] [SPARK-11338][WebUI] nit fixes
d054bd7 [Christian Kadner] [SPARK-11338][WebUI] prependBaseUri in method makePageLink
8bcb3dc [Christian Kadner] [SPARK-11338][WebUI] Prepend application links on HistoryPage with uiRoot path

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

@@ -161,7 +161,7 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
       info: ApplicationHistoryInfo,
       attempt: ApplicationAttemptInfo,
       isFirst: Boolean): Seq[Node] = {
-    val uiAddress = HistoryServer.getAttemptURI(info.id, attempt.attemptId)
+    val uiAddress = UIUtils.prependBaseUri(HistoryServer.getAttemptURI(info.id, attempt.attemptId))
     val startTime = UIUtils.formatDate(attempt.startTime)
     val endTime = if (attempt.endTime > 0) UIUtils.formatDate(attempt.endTime) else "-"
     val duration =
@@ -190,8 +190,7 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
       {
         if (renderAttemptIdColumn) {
           if (info.attempts.size > 1 && attempt.attemptId.isDefined) {
-            <td><a href={HistoryServer.getAttemptURI(info.id, attempt.attemptId)}>
-              {attempt.attemptId.get}</a></td>
+            <td><a href={uiAddress}>{attempt.attemptId.get}</a></td>
           } else {
             <td>&nbsp;</td>
           }
@@ -218,9 +217,9 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
   }
 
   private def makePageLink(linkPage: Int, showIncomplete: Boolean): String = {
-    "/?" + Array(
+    UIUtils.prependBaseUri("/?" + Array(
       "page=" + linkPage,
       "showIncomplete=" + showIncomplete
-    ).mkString("&")
+      ).mkString("&"))
   }
 }

core/src/test/scala/org/apache/spark/deploy/history/HistoryServerSuite.scala

@@ -29,7 +29,7 @@ import org.scalatest.{BeforeAndAfter, Matchers}
 import org.scalatest.mock.MockitoSugar
 
 import org.apache.spark.{JsonTestUtils, SecurityManager, SparkConf, SparkFunSuite}
-import org.apache.spark.ui.SparkUI
+import org.apache.spark.ui.{SparkUI, UIUtils}
 
 /**
  * A collection of tests against the historyserver, including comparing responses from the json
@@ -261,7 +261,24 @@ class HistoryServerSuite extends SparkFunSuite with BeforeAndAfter with Matchers
       l <- links
       attrs <- l.attribute("href")
     } yield (attrs.toString)
-    justHrefs should contain(link)
+    justHrefs should contain (UIUtils.prependBaseUri(resource = link))
+  }
+
+  test("relative links are prefixed with uiRoot (spark.ui.proxyBase)") {
+    val proxyBaseBeforeTest = System.getProperty("spark.ui.proxyBase")
+    val uiRoot = Option(System.getenv("APPLICATION_WEB_PROXY_BASE")).getOrElse("/testwebproxybase")
+    val page = new HistoryPage(server)
+    val request = mock[HttpServletRequest]
+
+    // when
+    System.setProperty("spark.ui.proxyBase", uiRoot)
+    val response = page.render(request)
+    System.setProperty("spark.ui.proxyBase", Option(proxyBaseBeforeTest).getOrElse(""))
+
+    // then
+    val urls = response \\ "@href" map (_.toString)
+    val siteRelativeLinks = urls filter (_.startsWith("/"))
+    all (siteRelativeLinks) should startWith (uiRoot)
   }
 
   def getContentAndCode(path: String, port: Int = port): (Int, Option[String], Option[String]) = {