Step 2: Add Akka Cluster Sharding features

build.sbt

@@ -13,8 +13,7 @@ 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-cluster-sharding"       %  akkaVersion,
     "com.typesafe.akka"  %%  "akka-http"                   %  akkaHttpVersion,
     "com.typesafe.akka"  %%  "akka-stream"                 %  akkaVersion,
     "de.heikoseeberger"  %%  "akka-http-json4s"            %  akkaHttpJson4sVersion,

src/main/scala/HttpServerApp.scala

@@ -1,5 +1,5 @@
-import akka.actor.{ActorSystem, PoisonPill}
-import akka.cluster.singleton.{ClusterSingletonManager, ClusterSingletonManagerSettings, ClusterSingletonProxy, ClusterSingletonProxySettings}
+import akka.actor.ActorSystem
+import akka.cluster.sharding.{ClusterSharding, ClusterShardingSettings}
 import akka.event.Logging
 import akka.http.scaladsl.Http
 import akka.http.scaladsl.server.Directives
@@ -8,7 +8,7 @@ import api.{CustomExceptionHandling, EventHttpEndpoint}
 import com.typesafe.config.{Config, ConfigFactory}
 import persistence.EventRepository
 import reactivemongo.api.{MongoConnection, MongoDriver}
-import services.{EventManager, TicketSellerSupervisor}
+import services.{EventManager, TicketSeller}
 
 import scala.concurrent.Await
 import scala.concurrent.duration._
@@ -45,24 +45,16 @@ trait PersistenceModule { self: AkkaModule with SettingsModule =>
 }
 
 trait ServicesModule { self: AkkaModule with PersistenceModule =>
-  // 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)
+  // Initiates ShardRegion for TicketSeller
+  val ticketSellerShardRegion =
+    ClusterSharding(system).start(
+      typeName = TicketSeller.Name,
+      entityProps = TicketSeller.props(),
+      settings = ClusterShardingSettings(system),
+      extractEntityId = TicketSeller.Sharding.extractEntityId,
+      extractShardId = TicketSeller.Sharding.extractShardId)
+
+  val eventManager = system.actorOf(EventManager.props(eventRepository, ticketSellerShardRegion), EventManager.Name)
 }
 
 trait EndpointsModule { self: AkkaModule with ServicesModule =>

src/main/scala/services/TicketSeller.scala

@@ -1,6 +1,7 @@
 package services
 
 import akka.actor.{Actor, FSM, Props}
+import akka.cluster.sharding.ShardRegion
 import domain.{Ticket, _}
 
 object TicketSeller {
@@ -37,6 +38,16 @@ object TicketSeller {
     }
   }
 
+  object Sharding {
+    val extractEntityId: ShardRegion.ExtractEntityId = {
+      case msg @ EventMessage(jobId, _) => (jobId.toString, msg)
+    }
+
+    val extractShardId: ShardRegion.ExtractShardId = {
+      case EventMessage(jobId, _) => (math.abs(jobId.toString.hashCode) % 100).toString
+    }
+  }
+
 }
 
 class TicketSeller extends Actor with FSM[TicketSeller.State, TicketSeller.BoxOffice] {