Added log messages when leadership is gained or lost (#25053)

akka-cluster/src/test/scala/akka/cluster/ClusterLogSpec.scala

@@ -0,0 +1,57 @@
+/**
+ *  Copyright (C) 2009-2018 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.cluster
+
+import akka.actor.{ Address, ExtendedActorSystem }
+import akka.cluster.InternalClusterAction.LeaderActionsTick
+import akka.testkit.{ AkkaSpec, EventFilter, ImplicitSender }
+
+object ClusterLogSpec {
+  val config = """
+    akka.cluster {
+      auto-down-unreachable-after = 0s
+      publish-stats-interval = 0 s # always, when it happens
+      failure-detector.implementation-class = akka.cluster.FailureDetectorPuppet
+    }
+    akka.actor.provider = "cluster"
+    akka.remote.log-remote-lifecycle-events = off
+    akka.remote.netty.tcp.port = 0
+    akka.remote.artery.canonical.port = 0
+    akka.loglevel = "INFO"
+    akka.loggers = ["akka.testkit.TestEventListener"]
+    """
+
+}
+
+class ClusterLogSpec extends AkkaSpec(ClusterLogSpec.config) with ImplicitSender {
+
+  val selfAddress: Address = system.asInstanceOf[ExtendedActorSystem].provider.getDefaultAddress
+
+  val cluster = Cluster(system)
+  def clusterView: ClusterReadView = cluster.readView
+
+  "A Cluster" must {
+
+    "Log a message when becoming and stopping being a leader" in {
+      EventFilter
+        .info(occurrences = 1, pattern = "is the new leader")
+        .intercept {
+          cluster.join(selfAddress)
+        }
+
+      awaitCond(clusterView.isSingletonCluster)
+      clusterView.self.address should ===(selfAddress)
+      clusterView.members.map(_.address) should ===(Set(selfAddress))
+      awaitAssert(clusterView.status should ===(MemberStatus.Up))
+
+      EventFilter
+        .info(occurrences = 1, pattern = "is no longer the leader")
+        .intercept {
+          cluster.down(selfAddress)
+        }
+    }
+
+  }
+}