[LIVY-415][CORE][FOLLOWUP] Fix static object creation issue for SessionState

## What changes were proposed in this pull request?

In LIVY-415, we changed `SessionState` to static object instead of case class. This is OK for `SessionState`, but for `FinishedSessionState`, it requires `time` field to be set during object creation. Using static object will never reflect the actual `time` when object is created. So here propose to fix it.

CC aa8y please take a review, this is introduced in your changes.

## How was this patch tested?

Existing tests.

Author: jerryshao <sshao@hortonworks.com>

Closes #67 from jerryshao/LIVY-415-followup.

core/src/main/scala/org/apache/livy/sessions/SessionState.scala

@@ -37,9 +37,9 @@ object SessionState {
     case "running" => Running
     case "busy" => Busy
     case "shutting_down" => ShuttingDown
-    case "error" => Error
-    case "dead" => Dead
-    case "success" => Success
+    case "error" => Error()
+    case "dead" => Dead()
+    case "success" => Success()
     case _ => throw new IllegalArgumentException(s"Illegal session state: $s")
   }
 
@@ -57,15 +57,12 @@ object SessionState {
 
   object ShuttingDown extends SessionState("shutting_down", false)
 
-  case class Error(override val time: Long) extends
+  case class Error(override val time: Long = System.nanoTime()) extends
     FinishedSessionState("error", true, time)
-  object Error extends Error(System.nanoTime)
 
-  case class Dead(override val time: Long) extends
+  case class Dead(override val time: Long = System.nanoTime()) extends
     FinishedSessionState("dead", false, time)
-  object Dead extends Dead(System.nanoTime)
 
-  case class Success(override val time: Long) extends
+  case class Success(override val time: Long = System.nanoTime()) extends
     FinishedSessionState("success", false, time)
-  object Success extends Success(System.nanoTime)
 }

integration-test/src/main/scala/org/apache/livy/test/framework/LivyRestClient.scala

@@ -111,9 +111,9 @@ class LivyRestClient(val httpClient: AsyncHttpClient, val livyEndpoint: String)
   }
 
   class BatchSession(id: Int) extends Session(id, BATCH_TYPE) {
-    def verifySessionDead(): Unit = verifySessionState(SessionState.Dead)
+    def verifySessionDead(): Unit = verifySessionState(SessionState.Dead())
     def verifySessionRunning(): Unit = verifySessionState(SessionState.Running)
-    def verifySessionSuccess(): Unit = verifySessionState(SessionState.Success)
+    def verifySessionSuccess(): Unit = verifySessionState(SessionState.Success())
   }
 
   class InteractiveSession(id: Int) extends Session(id, INTERACTIVE_TYPE) {
@@ -226,7 +226,7 @@ class LivyRestClient(val httpClient: AsyncHttpClient, val livyEndpoint: String)
         .setBody(mapper.writeValueAsString(requestBody))
         .execute()
 
-      verifySessionState(SessionState.Dead)
+      verifySessionState(SessionState.Dead())
     }
 
     def verifySessionIdle(): Unit = {

repl/src/main/scala/org/apache/livy/repl/Session.scala

@@ -136,7 +136,7 @@ class Session(
       entries
     }(interpreterExecutor)
 
-    future.onFailure { case _ => changeState(SessionState.Error) }(interpreterExecutor)
+    future.onFailure { case _ => changeState(SessionState.Error()) }(interpreterExecutor)
     future
   }
 
@@ -297,7 +297,7 @@ class Session(
               (TRACEBACK -> traceback)
 
           case Interpreter.ExecuteAborted(message) =>
-            changeState(SessionState.Error)
+            changeState(SessionState.Error())
 
             (STATUS -> ERROR) ~
               (EXECUTION_COUNT -> executionCount) ~

server/src/main/scala/org/apache/livy/server/batch/BatchSession.scala

@@ -178,9 +178,9 @@ class BatchSession(
           _state = SessionState.Running
           info(s"Batch session $id created [appid: ${appId.orNull}, state: ${state.toString}, " +
             s"info: ${appInfo.asJavaMap}]")
-        case SparkApp.State.FINISHED => _state = SessionState.Success
+        case SparkApp.State.FINISHED => _state = SessionState.Success()
         case SparkApp.State.KILLED | SparkApp.State.FAILED =>
-          _state = SessionState.Dead
+          _state = SessionState.Dead()
         case _ =>
       }
     }

server/src/main/scala/org/apache/livy/server/interactive/InteractiveSession.scala

@@ -398,7 +398,7 @@ class InteractiveSession(
   }
 
   if (client.isEmpty) {
-    transition(Dead)
+    transition(Dead())
     val msg = s"Cannot recover interactive session $id because its RSCDriver URI is unknown."
     info(msg)
     sessionLog = IndexedSeq(msg)
@@ -435,7 +435,7 @@ class InteractiveSession(
         // this callback might be triggered. Check and don't call stop() to avoid nested called
         // if the session is already shutting down.
         if (serverSideState != SessionState.ShuttingDown) {
-          transition(SessionState.Error)
+          transition(SessionState.Error())
           stop()
           app.foreach { a =>
             info(s"Failed to ping RSC driver for session $id. Killing application.")
@@ -474,7 +474,7 @@ class InteractiveSession(
           _.kill()
         }
     } finally {
-      transition(SessionState.Dead)
+      transition(SessionState.Dead())
     }
   }
 
@@ -611,7 +611,7 @@ class InteractiveSession(
       debug(s"$this app state changed from $oldState to $newState")
       newState match {
         case SparkApp.State.FINISHED | SparkApp.State.KILLED | SparkApp.State.FAILED =>
-          transition(SessionState.Dead)
+          transition(SessionState.Dead())
         case _ =>
       }
     }

server/src/test/scala/org/apache/livy/sessions/SessionManagerSpec.scala

@@ -98,9 +98,9 @@ class SessionManagerSpec extends FunSpec with Matchers with LivyBaseUnitTestSuit
       }
 
       // Stopped session should be gc-ed after retained timeout
-      for (s <- Seq(SessionState.Error,
-        SessionState.Success,
-        SessionState.Dead)) {
+      for (s <- Seq(SessionState.Error(),
+        SessionState.Success(),
+        SessionState.Dead())) {
         eventually(timeout(30 seconds), interval(100 millis)) {
           changeStateAndCheck(s) { sm => sm.get(session.id) should be (None) }
         }