Add close() method to Coordination for resource cleanup

coordination-etcd/src/main/scala/de/heikoseeberger/constructr/coordination/etcd/EtcdCoordination.scala

@@ -162,6 +162,9 @@ final class EtcdCoordination(clusterName: String, system: ActorSystem) extends C
   override def refresh(self: Address, ttl: FiniteDuration) =
     addSelfOrRefresh(self, ttl)
 
+  override def close(): Future[Done] =
+    Future.successful(Done)
+
   private def addSelfOrRefresh(self: Address, ttl: FiniteDuration) = {
     val node  = getUrlEncoder.encodeToString(self.toString.getBytes(UTF_8))
     val query = Uri.Query("ttl" -> toSeconds(ttl), "value" -> self.toString)

coordination/src/main/scala/de/heikoseeberger/constructr/coordination/Coordination.scala

@@ -55,11 +55,11 @@ trait Coordination {
   def getNodes(): Future[Set[Address]]
 
   /**
-    * Akquire a lock for bootstrapping the cluster (first node).
+    * Acquire a lock for bootstrapping the cluster (first node).
     *
     * @param self self node
     * @param ttl TTL for the lock
-    * @return true, if lock could be akquired, else false
+    * @return true, if lock could be acquired, else false
     */
   def lock(self: Address, ttl: FiniteDuration): Future[Boolean]
 
@@ -80,4 +80,11 @@ trait Coordination {
     * @return future signaling done
     */
   def refresh(self: Address, ttl: FiniteDuration): Future[Done]
+
+  /**
+    * Performs resource cleanup on termination
+    *
+    * @return future signaling done
+    */
+  def close(): Future[Done]
 }

core/src/main/scala/de/heikoseeberger/constructr/ConstructrMachine.scala

@@ -22,9 +22,9 @@ import akka.actor.{ Address, FSM, Props, Status }
 import akka.cluster.Cluster
 import akka.cluster.ClusterEvent.{ InitialStateAsEvents, MemberJoined, MemberUp }
 import akka.pattern.pipe
-import akka.stream.ActorMaterializer
 import de.heikoseeberger.constructr.coordination.Coordination
 import scala.concurrent.duration.{ Duration, FiniteDuration }
+import scala.util.{ Success, Failure => SFailure }
 
 object ConstructrMachine {
 
@@ -105,8 +105,7 @@ final class ConstructrMachine(
     s"ttl-factor must be greater or equal 1 + ((coordination-timeout * (1 + nr-of-retries) + retry-delay * nr-of-retries)/ refresh-interval), i.e. $minTtlFactor, but was $ttlFactor!"
   )
 
-  private implicit val mat = ActorMaterializer()
-  private val cluster      = Cluster(context.system)
+  private val cluster = Cluster(context.system)
 
   startWith(State.GettingNodes, Data(Set.empty, State.GettingNodes, nrOfRetries))
 
@@ -295,6 +294,18 @@ final class ConstructrMachine(
 
   initialize()
 
+  // Performs resource cleanup on termination
+
+  onTermination {
+    case se: StopEvent =>
+      log.warning("StopEvent received, reason: {}. Closing Coordinator for resource cleanup",
+                  se.reason)
+      coordination.close().onComplete {
+        case Success(_)  => log.info("Coordinator closed successfully")
+        case SFailure(e) => log.error(e, "Coordinator failed to close")
+      }
+  }
+
   // Helpers
 
   private def retry(retryState: ConstructrMachine.State) =

core/src/test/scala/de/heikoseeberger/constructr/ConstructrMachineSpec.scala

@@ -45,6 +45,9 @@ final class ConstructrMachineSpec extends WordSpec with Matchers with BeforeAndA
         boom(),
         delayed(1.hour.dilated, system.scheduler)(noNodes())
       )
+      when(coordination.close()).thenReturn(
+        Future.successful(Done)
+      )
 
       val monitor = TestProbe()
       val machine = system.actorOf(
@@ -103,6 +106,9 @@ final class ConstructrMachineSpec extends WordSpec with Matchers with BeforeAndA
         boom(),
         Future.successful(Done)
       )
+      when(coordination.close()).thenReturn(
+        Future.successful(Done)
+      )
 
       val monitor = TestProbe()
       val machine = system.actorOf(
@@ -228,6 +234,10 @@ final class ConstructrMachineSpec extends WordSpec with Matchers with BeforeAndA
         Future.successful(Done)
       )
 
+      when(coordination.close()).thenReturn(
+        Future.successful(Done)
+      )
+
       val nrOfRetries = 2
       val monitor     = TestProbe()
       val machine = system.actorOf(