Use Either for LeaderChanged state, see #2518

akka-cluster/src/main/scala/akka/cluster/ClusterEvent.scala

@@ -173,8 +173,14 @@ private[cluster] final class ClusterDomainEventPublisher extends Actor with Acto
   import InternalClusterAction._
 
   var latestGossip: Gossip = Gossip()
-  var stashedLeaderChanged: Option[LeaderChanged] = None
-  var publishedLeaderChanged: Option[LeaderChanged] = None
+
+  // Keep track of LeaderChanged event. Should not be published until
+  // convergence, and it should only be published when leader actually
+  // changed to another node. 3 states:
+  // - None: No LeaderChanged detected yet, nothing published yet
+  // - Some(Left): Stashed LeaderChanged to be published later, when convergence
+  // - Some(Right): Latest published LeaderChanged
+  var leaderChangedState: Option[Either[LeaderChanged, LeaderChanged]] = None
 
   def receive = {
     case PublishChanges(oldGossip, newGossip) ⇒ publishChanges(oldGossip, newGossip)
@@ -204,23 +210,26 @@ private[cluster] final class ClusterDomainEventPublisher extends Actor with Acto
     latestGossip = newGossip
     diff(oldGossip, newGossip) foreach { event ⇒
       event match {
-        case x @ LeaderChanged(_) if Some(x) == publishedLeaderChanged ⇒
+        case x @ LeaderChanged(_) if leaderChangedState == Some(Right(x)) ⇒
         // skip, this leader has already been published
 
         case x @ LeaderChanged(_) if oldGossip.convergence && newGossip.convergence ⇒
-          stashedLeaderChanged = None
-          publishedLeaderChanged = Some(x)
+          // leader changed and immediate convergence
+          leaderChangedState = Some(Right(x))
           eventStream publish x
 
         case x: LeaderChanged ⇒
           // publish later, when convergence
-          stashedLeaderChanged = Some(x)
+          leaderChangedState = Some(Left(x))
 
         case ConvergenceChanged(true) ⇒
-          stashedLeaderChanged foreach {
-            publishedLeaderChanged = stashedLeaderChanged
-            stashedLeaderChanged = None
-            eventStream publish _
+          // now it's convergence, publish eventual stashed LeaderChanged event
+          leaderChangedState match {
+            case Some(Left(x)) ⇒
+              leaderChangedState = Some(Right(x))
+              eventStream publish x
+
+            case _ ⇒ // nothing stashed
           }
           eventStream publish event
 
@@ -228,7 +237,10 @@ private[cluster] final class ClusterDomainEventPublisher extends Actor with Acto
           eventStream publish event
           // notify DeathWatch about unreachable node
           eventStream publish AddressTerminated(m.address)
-        case _ ⇒ eventStream publish event
+
+        case _ ⇒
+          // all other events
+          eventStream publish event
       }
     }
   }