[SPARK-28564][CORE] Access history application defaults to the last attempt id

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

@@ -79,7 +79,18 @@ class HistoryServer(
       }
 
       val appId = parts(1)
-      val attemptId = if (parts.length >= 3) Some(parts(2)) else None
+      var shouldAppendAttemptId = false
+      val attemptId = if (parts.length >= 3) {
+        Some(parts(2))
+      } else {
+        val lastAttemptId = provider.getApplicationInfo(appId).flatMap(_.attempts.head.attemptId)
+        if (lastAttemptId.isDefined) {
+          shouldAppendAttemptId = true
+          lastAttemptId
+        } else {
+          None
+        }
+      }
 
       // Since we may have applications with multiple attempts mixed with applications with a
       // single attempt, we need to try both. Try the single-attempt route first, and if an
@@ -97,7 +108,17 @@ class HistoryServer(
       // the app's UI, and all we need to do is redirect the user to the same URI that was
       // requested, and the proper data should be served at that point.
       // Also, make sure that the redirect url contains the query string present in the request.
-      val requestURI = req.getRequestURI + Option(req.getQueryString).map("?" + _).getOrElse("")
+      val attemptPart = if (shouldAppendAttemptId) {
+        if (!req.getRequestURI.endsWith("/")) {
+          "/" + attemptId.get
+        } else {
+          attemptId.get
+        }
+      } else {
+        ""
+      }
+      val requestURI = req.getRequestURI +
+        attemptPart + Option(req.getQueryString).map("?" + _).getOrElse("")
       res.sendRedirect(res.encodeRedirectURL(requestURI))
     }
 

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

@@ -632,6 +632,49 @@ class HistoryServerSuite extends SparkFunSuite with BeforeAndAfter with Matchers
     }
   }
 
+  test("SPARK-28564: Access history application defaults to the last attempt id") {
+
+    def getRedirectUrl(url: URL): (Int, String) = {
+      val connection = url.openConnection().asInstanceOf[HttpURLConnection]
+      connection.setRequestMethod("GET")
+      connection.setUseCaches(false)
+      connection.setDefaultUseCaches(false)
+      connection.setInstanceFollowRedirects(false)
+      connection.connect()
+      val code = connection.getResponseCode()
+      val location = connection.getHeaderField("Location")
+      (code, location)
+    }
+
+    def buildPageAttemptUrl(appId: String, attemptId: Option[Int]): URL = {
+      attemptId match {
+        case Some(id) =>
+          new URL(s"http://localhost:$port/history/$appId/$id")
+        case None =>
+          new URL(s"http://localhost:$port/history/$appId")
+      }
+    }
+
+    val oneAttemptAppId = "local-1430917381534"
+    HistoryServerSuite.getUrl(buildPageAttemptUrl(oneAttemptAppId, None))
+
+    val multiAttemptAppid = "local-1430917381535"
+    val lastAttemptId = Some(2)
+    val lastAttemptUrl = buildPageAttemptUrl(multiAttemptAppid, lastAttemptId)
+    Seq(None, Some(1), Some(2)).foreach { attemptId =>
+      val url = buildPageAttemptUrl(multiAttemptAppid, attemptId)
+      val (code, location) = getRedirectUrl(url)
+      assert(code === 302, s"Unexpected status code $code for $url")
+      attemptId match {
+        case None =>
+          assert(location.stripSuffix("/") === lastAttemptUrl.toString, s"Unexpected url")
+        case _ =>
+          assert(location.stripSuffix("/") === url.toString, s"Unexpected url")
+      }
+      HistoryServerSuite.getUrl(new URL(location))
+    }
+  }
+
   def getContentAndCode(path: String, port: Int = port): (Int, Option[String], Option[String]) = {
     HistoryServerSuite.getContentAndCode(new URL(s"http://localhost:$port/api/v1/$path"))
   }