Added FSM to the Node's ClusterCommandDaemon to manage the cluster command state as an FSM. Also added tests for all the FSM state changes.

Signed-off-by: Jonas Bonér <jonas@jonasboner.com>

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

@@ -46,24 +46,48 @@ trait MetaDataChangeListener { // FIXME add management and notification for Meta
 sealed trait ClusterMessage extends Serializable
 
 /**
- * Command to join the cluster.
+ * Cluster commands sent by the USER.
  */
-case class Join(node: Address) extends ClusterMessage
+object UserAction {
 
-/**
+  /**
+   * Command to join the cluster. Sent when a node (reprsesented by 'address')
+   * wants to join another node (the receiver).
+   */
+  case class Join(address: Address) extends ClusterMessage
+
+  /**
    * Command to leave the cluster.
    */
-case class Leave(node: Address) extends ClusterMessage
+  case object Leave extends ClusterMessage
 
-/**
- * Command to mark node as temporay down.
+  /**
+   * Command to mark node as temporary down.
    */
-case class Down(node: Address) extends ClusterMessage
+  case object Down extends ClusterMessage
+
+  /**
+   * Command to mark a node to be removed from the cluster immediately.
+   */
+  case object Exit extends ClusterMessage
+}
 
 /**
+ * Cluster commands sent by the LEADER.
+ * Node: Leader can also send UserActions but not vice versa.
+ */
+object LeaderAction {
+
+  /**
+   * Command to set a node to Up (from Joining).
+   */
+  case object Up extends ClusterMessage
+
+  /**
    * Command to remove a node from the cluster immediately.
    */
-case class Remove(node: Address) extends ClusterMessage
+  case object Remove extends ClusterMessage
+}
 
 /**
  * Represents the address and the current status of a cluster member node.
@@ -87,6 +111,7 @@ object MemberStatus {
   case object Leaving extends MemberStatus
   case object Exiting extends MemberStatus
   case object Down extends MemberStatus
+  case object Removed extends MemberStatus
 }
 
 // sealed trait PartitioningStatus
@@ -153,20 +178,92 @@ case class Gossip(
       ")"
 }
 
-// FIXME ClusterCommandDaemon with FSM trait
 /**
- * Single instance. FSM managing the different cluster nodes states.
- * Serialized access to Node.
+ * FSM actor managing the different cluster nodes states.
+ * Single instance - e.g. serialized access to Node - message after message.
  */
-final class ClusterCommandDaemon(system: ActorSystem, node: Node) extends Actor {
-  val log = Logging(system, "ClusterCommandDaemon")
+final class ClusterCommandDaemon(system: ActorSystem, node: Node) extends Actor with FSM[MemberStatus, Unit] {
 
-  def receive = {
-    case Join(address)   ⇒ node.joining(address)
-    case Leave(address)  ⇒ //node.leaving(address)
-    case Down(address)   ⇒ //node.downing(address)
-    case Remove(address) ⇒ //node.removing(address)
-    case unknown         ⇒ log.error("Unknown message sent to cluster daemon [" + unknown + "]")
+  // start in JOINING
+  startWith(MemberStatus.Joining, Unit)
+
+  // ========================
+  // === IN JOINING ===
+  when(MemberStatus.Joining) {
+    case Event(LeaderAction.Up, _) ⇒
+      node.up()
+      goto(MemberStatus.Up)
+  }
+
+  // ========================
+  // === IN UP ===
+  when(MemberStatus.Up) {
+    case Event(UserAction.Down, _) ⇒
+      node.downing()
+      goto(MemberStatus.Down)
+
+    case Event(UserAction.Leave, _) ⇒
+      node.leaving()
+      goto(MemberStatus.Leaving)
+
+    case Event(UserAction.Exit, _) ⇒
+      node.exiting()
+      goto(MemberStatus.Exiting)
+
+    case Event(LeaderAction.Remove, _) ⇒
+      node.removing()
+      goto(MemberStatus.Removed)
+  }
+
+  // ========================
+  // === IN LEAVING ===
+  when(MemberStatus.Leaving) {
+    case Event(UserAction.Down, _) ⇒
+      node.downing()
+      goto(MemberStatus.Down)
+
+    case Event(LeaderAction.Remove, _) ⇒
+      node.removing()
+      goto(MemberStatus.Removed)
+  }
+
+  // ========================
+  // === IN EXITING ===
+  when(MemberStatus.Exiting) {
+    case Event(LeaderAction.Remove, _) ⇒
+      node.removing()
+      goto(MemberStatus.Removed)
+  }
+
+  // ========================
+  // === IN DOWN ===
+  when(MemberStatus.Down) {
+    // FIXME How to transition from DOWN => JOINING when node comes back online. Can't just listen to Gossip message since it is received be another actor. How to fix this?
+    case Event(LeaderAction.Remove, _) ⇒
+      node.removing()
+      goto(MemberStatus.Removed)
+  }
+
+  // ========================
+  // === IN REMOVED ===
+  when(MemberStatus.Removed) {
+    case command ⇒
+      log.warning("Removed node [{}] received cluster   command [{}]", system.name, command)
+      stay
+  }
+
+  // ========================
+  // === GENERIC AND UNHANDLED COMMANDS ===
+  whenUnhandled {
+    // should be able to handle Join in any state
+    case Event(UserAction.Join(address), _) ⇒
+      node.joining(address)
+      stay
+
+    case Event(command, _) ⇒ {
+      log.warning("Unhandled command [{}] in state [{}]", command, stateName)
+      stay
+    }
   }
 }
 
@@ -274,7 +371,7 @@ class Node(system: ActorSystemImpl) extends Extension {
   log.info("Node [{}] - Starting cluster Node...", remoteAddress)
 
   // try to join the node defined in the 'akka.cluster.node-to-join' option
-  join()
+  autoJoin()
 
   // start periodic gossip to random nodes in cluster
   private val gossipCanceller = system.scheduler.schedule(gossipInitialDelay, gossipFrequency) {
@@ -369,6 +466,7 @@ class Node(system: ActorSystemImpl) extends Extension {
   // ========================================================
 
   /**
+   * State transition to JOINING.
    * New node joining.
    */
   @tailrec
@@ -397,6 +495,31 @@ class Node(system: ActorSystemImpl) extends Extension {
     }
   }
 
+  /**
+   * State transition to UP.
+   */
+  private[cluster] final def up() {}
+
+  /**
+   * State transition to LEAVING.
+   */
+  private[cluster] final def leaving() {}
+
+  /**
+   * State transition to EXITING.
+   */
+  private[cluster] final def exiting() {}
+
+  /**
+   * State transition to REMOVED.
+   */
+  private[cluster] final def removing() {}
+
+  /**
+   * State transition to DOWN.
+   */
+  private[cluster] final def downing() {}
+
   /**
    * Receive new gossip.
    */
@@ -444,9 +567,9 @@ class Node(system: ActorSystemImpl) extends Extension {
   /**
    * Joins the pre-configured contact point and retrieves current gossip state.
    */
-  private def join() = nodeToJoin foreach { address ⇒
+  private def autoJoin() = nodeToJoin foreach { address ⇒
     val connection = clusterCommandConnectionFor(address)
-    val command = Join(remoteAddress)
+    val command = UserAction.Join(remoteAddress)
     log.info("Node [{}] - Sending [{}] to [{}] through connection [{}]", remoteAddress, command, address, connection)
     connection ! command
   }
@@ -501,16 +624,18 @@ class Node(system: ActorSystemImpl) extends Extension {
   }
 
   /**
-   * Switches the state in the FSM.
+   * Switches the member status.
+   *
+   * @param newStatus the new member status
+   * @param oldState the state to change the member status in
+   * @return the updated new state with the new member status
    */
-  @tailrec
-  final private def switchStatusTo(newStatus: MemberStatus) {
+  private def switchMemberStatusTo(newStatus: MemberStatus, state: State): State = {
     log.info("Node [{}] - Switching membership status to [{}]", remoteAddress, newStatus)
 
-    val localState = state.get
-    val localSelf = localState.self
+    val localSelf = state.self
 
-    val localGossip = localState.latestGossip
+    val localGossip = state.latestGossip
     val localMembers = localGossip.members
 
     val newSelf = localSelf copy (status = newStatus)
@@ -526,9 +651,7 @@ class Node(system: ActorSystemImpl) extends Extension {
     val versionedGossip = newGossip + vclockNode
     val seenVersionedGossip = versionedGossip seen remoteAddress
 
-    val newState = localState copy (self = newSelf, latestGossip = seenVersionedGossip)
-
-    if (!state.compareAndSet(localState, newState)) switchStatusTo(newStatus) // recur if we failed update
+    state copy (self = newSelf, latestGossip = seenVersionedGossip)
   }
 
   /**

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

@@ -1,3 +1,7 @@
+/**
+ * Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
+ */
+
 package akka.cluster
 
 import java.net.InetSocketAddress

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

@@ -0,0 +1,156 @@
+/**
+ * Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.cluster
+
+import akka.testkit._
+import akka.actor.Address
+
+class ClusterCommandDaemonFSMSpec extends AkkaSpec(
+  """
+  akka {
+    actor {
+      provider = akka.remote.RemoteActorRefProvider
+    }
+  }
+  """) with ImplicitSender {
+
+  "A ClusterCommandDaemon FSM" must {
+
+    "start in Joining" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+    }
+
+    "be able to switch from Joining to Up" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+    }
+
+    "be able to switch from Up to Down" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Down
+      fsm.stateName must be(MemberStatus.Down)
+    }
+
+    "be able to switch from Up to Leaving" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Leave
+      fsm.stateName must be(MemberStatus.Leaving)
+    }
+
+    "be able to switch from Up to Exiting" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Exit
+      fsm.stateName must be(MemberStatus.Exiting)
+    }
+
+    "be able to switch from Up to Removed" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! LeaderAction.Remove
+      fsm.stateName must be(MemberStatus.Removed)
+    }
+
+    "be able to switch from Leaving to Down" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Leave
+      fsm.stateName must be(MemberStatus.Leaving)
+      fsm ! UserAction.Down
+      fsm.stateName must be(MemberStatus.Down)
+    }
+
+    "be able to switch from Leaving to Removed" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Leave
+      fsm.stateName must be(MemberStatus.Leaving)
+      fsm ! LeaderAction.Remove
+      fsm.stateName must be(MemberStatus.Removed)
+    }
+
+    "be able to switch from Exiting to Removed" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Exit
+      fsm.stateName must be(MemberStatus.Exiting)
+      fsm ! LeaderAction.Remove
+      fsm.stateName must be(MemberStatus.Removed)
+    }
+
+    "be able to switch from Down to Removed" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Down
+      fsm.stateName must be(MemberStatus.Down)
+      fsm ! LeaderAction.Remove
+      fsm.stateName must be(MemberStatus.Removed)
+    }
+
+    "not be able to switch from Removed to any other state" in {
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! LeaderAction.Remove
+      fsm.stateName must be(MemberStatus.Removed)
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Removed)
+      fsm ! UserAction.Leave
+      fsm.stateName must be(MemberStatus.Removed)
+      fsm ! UserAction.Down
+      fsm.stateName must be(MemberStatus.Removed)
+      fsm ! UserAction.Exit
+      fsm.stateName must be(MemberStatus.Removed)
+      fsm ! LeaderAction.Remove
+      fsm.stateName must be(MemberStatus.Removed)
+    }
+
+    "remain in the same state when receiving a Join command" in {
+      val address = Address("akka", system.name)
+
+      val fsm = TestFSMRef(new ClusterCommandDaemon(system, system.node))
+      fsm.stateName must be(MemberStatus.Joining)
+      fsm ! UserAction.Join(address)
+      fsm.stateName must be(MemberStatus.Joining)
+
+      fsm ! LeaderAction.Up
+      fsm.stateName must be(MemberStatus.Up)
+      fsm ! UserAction.Join(address)
+      fsm.stateName must be(MemberStatus.Up)
+
+      fsm ! UserAction.Leave
+      fsm.stateName must be(MemberStatus.Leaving)
+      fsm ! UserAction.Join(address)
+      fsm.stateName must be(MemberStatus.Leaving)
+
+      fsm ! UserAction.Down
+      fsm.stateName must be(MemberStatus.Down)
+      fsm ! UserAction.Join(address)
+      fsm.stateName must be(MemberStatus.Down)
+    }
+  }
+}

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

@@ -1,6 +1,7 @@
 /**
  *  Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
  */
+
 package akka.cluster
 
 import akka.testkit._

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

@@ -1,3 +1,7 @@
+/**
+ * Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
+ */
+
 package akka.cluster
 
 import java.net.InetSocketAddress

akka-docs/scala/fsm.rst

@@ -440,7 +440,7 @@ and in the following.
 Event Tracing
 -------------
 
-The setting ``akka.actor.debug.fsm`` in `:ref:`configuration` enables logging of an
+The setting ``akka.actor.debug.fsm`` in :ref:`configuration` enables logging of an
 event trace by :class:`LoggingFSM` instances::
 
   class MyFSM extends Actor with LoggingFSM[X, Z] {