From 7277d03e7a4230ab38ac98081ce139b1548d1089 Mon Sep 17 00:00:00 2001
From: Patrik Nordwall <patrik.nordwall@gmail.com>
Date: Wed, 1 Jul 2015 15:09:16 +0200
Subject: [PATCH] =clu #15404 Require at least one subscribe class

* also check ClusterDomainEvent isAssignableFrom
---
 .../cluster/metrics/ClusterMetricsExtensionSpec.scala     | 3 +--
 akka-cluster/src/main/scala/akka/cluster/Cluster.scala    | 8 ++++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/akka-cluster-metrics/src/multi-jvm/scala/akka/cluster/metrics/ClusterMetricsExtensionSpec.scala b/akka-cluster-metrics/src/multi-jvm/scala/akka/cluster/metrics/ClusterMetricsExtensionSpec.scala
index 84a2f818d3..0d681b8b1f 100644
--- a/akka-cluster-metrics/src/multi-jvm/scala/akka/cluster/metrics/ClusterMetricsExtensionSpec.scala
+++ b/akka-cluster-metrics/src/multi-jvm/scala/akka/cluster/metrics/ClusterMetricsExtensionSpec.scala
@@ -151,8 +151,7 @@ abstract class ClusterMetricsDisabledSpec extends MultiNodeSpec(ClusterMetricsDi
       // TODO ensure same contract
       //clusterView.clusterMetrics.size should ===(0)
       metricsView.clusterMetrics.size should ===(0)
-      cluster.subscribe(testActor, classOf[ClusterMetricsChanged])
-      expectMsgType[CurrentClusterState]
+      ClusterMetricsExtension(system).subscribe(testActor)
       expectNoMsg
       // TODO ensure same contract
       //clusterView.clusterMetrics.size should ===(0)
diff --git a/akka-cluster/src/main/scala/akka/cluster/Cluster.scala b/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
index a61c0dbdb1..69fd6b0e75 100644
--- a/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
@@ -206,7 +206,7 @@ class Cluster(val system: ExtendedActorSystem) extends Extension {
    * will be sent to the subscriber as the first message.
    */
   @varargs def subscribe(subscriber: ActorRef, to: Class[_]*): Unit =
-    clusterCore ! InternalClusterAction.Subscribe(subscriber, initialStateMode = InitialStateAsSnapshot, to.toSet)
+    subscribe(subscriber, initialStateMode = InitialStateAsSnapshot, to: _*)
 
   /**
    * Subscribe to one or more cluster domain events.
@@ -223,8 +223,12 @@ class Cluster(val system: ExtendedActorSystem) extends Extension {
    *
    * Note that for large clusters it is more efficient to use `InitialStateAsSnapshot`.
    */
-  @varargs def subscribe(subscriber: ActorRef, initialStateMode: SubscriptionInitialStateMode, to: Class[_]*): Unit =
+  @varargs def subscribe(subscriber: ActorRef, initialStateMode: SubscriptionInitialStateMode, to: Class[_]*): Unit = {
+    require(to.length > 0, "at least one `ClusterDomainEvent` class is required")
+    require(to.forall(classOf[ClusterDomainEvent].isAssignableFrom),
+      s"subscribe to `akka.cluster.ClusterEvent.ClusterDomainEvent` or subclasses, was [${to.map(_.getName).mkString(", ")}]")
     clusterCore ! InternalClusterAction.Subscribe(subscriber, initialStateMode, to.toSet)
+  }
 
   /**
    * Unsubscribe to all cluster domain events.