Step 1: Add Akka Cluster features

build.sbt

@@ -13,6 +13,8 @@ libraryDependencies ++= {
   val logBackVersion = "1.2.3"
   Seq(
     "com.typesafe.akka"  %%  "akka-actor"                  %  akkaVersion,
+    "com.typesafe.akka"  %%  "akka-cluster"                %  akkaVersion,
+    "com.typesafe.akka"  %%  "akka-cluster-tools"          %  akkaVersion,
     "com.typesafe.akka"  %%  "akka-http"                   %  akkaHttpVersion,
     "com.typesafe.akka"  %%  "akka-stream"                 %  akkaVersion,
     "de.heikoseeberger"  %%  "akka-http-json4s"            %  akkaHttpJson4sVersion,

src/main/resources/application.conf

@@ -2,6 +2,33 @@ akka {
   loglevel = INFO
   stdout-loglevel = INFO
   loggers = ["akka.event.Logging$DefaultLogger"]
+
+  actor {
+    provider = "cluster"
+  }
+
+  remote {
+    log-remote-lifecycle-events = off
+
+    artery {
+      enabled = on
+      canonical.hostname = "127.0.0.1"
+      canonical.port = 2551
+      canonical.port = ${?akka.port}
+    }
+  }
+
+  cluster {
+    seed-nodes = [
+      "akka://reactive-tickets-system@127.0.0.1:2551",
+      "akka://reactive-tickets-system@127.0.0.1:2552"]
+
+    # auto downing is NOT safe for production deployments.
+    # you may want to use it during development, read more about it in the docs.
+    #
+    auto-down-unreachable-after = 10s
+  }
+
 }
 
 mongodb {

src/main/scala/HttpServerApp.scala

@@ -1,4 +1,5 @@
-import akka.actor.ActorSystem
+import akka.actor.{ActorSystem, PoisonPill}
+import akka.cluster.singleton.{ClusterSingletonManager, ClusterSingletonManagerSettings, ClusterSingletonProxy, ClusterSingletonProxySettings}
 import akka.event.Logging
 import akka.http.scaladsl.Http
 import akka.http.scaladsl.server.Directives
@@ -44,8 +45,24 @@ trait PersistenceModule { self: AkkaModule with SettingsModule =>
 }
 
 trait ServicesModule { self: AkkaModule with PersistenceModule =>
-  val ticketSellerSupervisor = system.actorOf(TicketSellerSupervisor.props(), TicketSellerSupervisor.Name)
-  val eventManager = system.actorOf(EventManager.props(eventRepository ,ticketSellerSupervisor), EventManager.Name)
+  // Initiates singleton TicketSellerSupervisor in the Cluster
+  val ticketSellerSupervisorSingleton =
+    system.actorOf(
+      ClusterSingletonManager.props(
+        singletonProps = TicketSellerSupervisor.props(),
+        terminationMessage = PoisonPill,
+        settings = ClusterSingletonManagerSettings(system).withSingletonName(s"${TicketSellerSupervisor.Name}-singleton")),
+      name = s"${TicketSellerSupervisor.Name}-singleton-manager")
+
+  // Initiates proxy for singleton
+  val ticketSellerSupervisorSingletonProxy =
+    system.actorOf(
+      ClusterSingletonProxy.props(
+        singletonManagerPath = ticketSellerSupervisorSingleton.path.toStringWithoutAddress,
+        settings = ClusterSingletonProxySettings(system).withSingletonName(s"${TicketSellerSupervisor.Name}-singleton")),
+      name = s"${TicketSellerSupervisor.Name}-singleton-proxy")
+
+  val eventManager = system.actorOf(EventManager.props(eventRepository, ticketSellerSupervisorSingletonProxy), EventManager.Name)
 }
 
 trait EndpointsModule { self: AkkaModule with ServicesModule =>