=clu,dc #23340 additional test to see a node take over monitoring of remote DC (#23342)

akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala

@@ -14,7 +14,7 @@ import akka.remote.testconductor.RoleName
 import akka.remote.testkit.{ FlightRecordingSupport, MultiNodeSpec, STMultiNodeSpec }
 import akka.testkit._
 import akka.testkit.TestEvent._
-import akka.actor.{ ActorSystem, Address }
+import akka.actor.{ Actor, ActorRef, ActorSystem, Address, Deploy, PoisonPill, Props, RootActorPath }
 import akka.event.Logging.ErrorLevel
 
 import scala.concurrent.duration._
@@ -22,9 +22,9 @@ import scala.collection.immutable
 import java.util.concurrent.ConcurrentHashMap
 
 import akka.remote.DefaultFailureDetectorRegistry
-import akka.actor.ActorRef
-import akka.actor.Actor
-import akka.actor.RootActorPath
+import akka.cluster.ClusterEvent.{ CurrentClusterState, MemberEvent, MemberExited, MemberRemoved }
+
+import scala.concurrent.Await
 
 object MultiNodeClusterSpec {
 
@@ -312,6 +312,46 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec with WatchedByCoro
     }
   }
 
+  def awaitMemberRemoved(toBeRemovedAddress: Address, timeout: FiniteDuration = 25.seconds): Unit = within(timeout) {
+    if (toBeRemovedAddress == cluster.selfAddress) {
+      enterBarrier("registered-listener")
+
+      cluster.leave(toBeRemovedAddress)
+      enterBarrier("member-left")
+
+      awaitCond(cluster.isTerminated, remaining)
+      enterBarrier("member-shutdown")
+    } else {
+      val exitingLatch = TestLatch()
+
+      val awaiter = system.actorOf(Props(new Actor {
+        def receive = {
+          case MemberRemoved(m, _) if m.address == toBeRemovedAddress ⇒
+            exitingLatch.countDown()
+          case _ ⇒
+          // ignore
+        }
+      }).withDeploy(Deploy.local))
+      cluster.subscribe(awaiter, classOf[MemberEvent])
+      enterBarrier("registered-listener")
+
+      // in the meantime member issues leave
+      enterBarrier("member-left")
+
+      // verify that the member is EXITING
+      try Await.result(exitingLatch, timeout) catch {
+        case cause: Exception ⇒
+          throw new AssertionError(s"Member ${toBeRemovedAddress} was not removed within ${timeout}!", cause)
+      }
+      awaiter ! PoisonPill // you've done your job, now die 
+
+      enterBarrier("member-shutdown")
+      markNodeAsUnavailable(toBeRemovedAddress)
+    }
+
+    enterBarrier("member-totally-shutdown")
+  }
+
   def awaitAllReachable(): Unit =
     awaitAssert(clusterView.unreachableMembers should ===(Set.empty))