Remove samples (#22288)

Add code, that was used for documentation to the appropriate projects
or akka-docs.

akka-docs/rst/scala/code/docs/cluster/FactorialFrontend.scala

@@ -0,0 +1,101 @@
+package scala.docs.cluster
+
+import scala.concurrent.duration._
+import com.typesafe.config.ConfigFactory
+import akka.actor.Actor
+import akka.actor.ActorLogging
+import akka.actor.ActorSystem
+import akka.actor.Props
+import akka.cluster.Cluster
+import akka.routing.FromConfig
+import akka.actor.ReceiveTimeout
+import scala.util.Try
+import scala.concurrent.Await
+
+//#frontend
+class FactorialFrontend(upToN: Int, repeat: Boolean) extends Actor with ActorLogging {
+
+  val backend = context.actorOf(
+    FromConfig.props(),
+    name = "factorialBackendRouter")
+
+  override def preStart(): Unit = {
+    sendJobs()
+    if (repeat) {
+      context.setReceiveTimeout(10.seconds)
+    }
+  }
+
+  def receive = {
+    case (n: Int, factorial: BigInt) =>
+      if (n == upToN) {
+        log.debug("{}! = {}", n, factorial)
+        if (repeat) sendJobs()
+        else context.stop(self)
+      }
+    case ReceiveTimeout =>
+      log.info("Timeout")
+      sendJobs()
+  }
+
+  def sendJobs(): Unit = {
+    log.info("Starting batch of factorials up to [{}]", upToN)
+    1 to upToN foreach { backend ! _ }
+  }
+}
+//#frontend
+
+object FactorialFrontend {
+  def main(args: Array[String]): Unit = {
+    val upToN = 200
+
+    val config = ConfigFactory.parseString("akka.cluster.roles = [frontend]").
+      withFallback(ConfigFactory.load("factorial"))
+
+    val system = ActorSystem("ClusterSystem", config)
+    system.log.info("Factorials will start when 2 backend members in the cluster.")
+    //#registerOnUp
+    Cluster(system) registerOnMemberUp {
+      system.actorOf(
+        Props(classOf[FactorialFrontend], upToN, true),
+        name = "factorialFrontend")
+    }
+    //#registerOnUp
+
+  }
+}
+
+// not used, only for documentation
+abstract class FactorialFrontend2 extends Actor {
+  //#router-lookup-in-code
+  import akka.cluster.routing.ClusterRouterGroup
+  import akka.cluster.routing.ClusterRouterGroupSettings
+  import akka.cluster.metrics.AdaptiveLoadBalancingGroup
+  import akka.cluster.metrics.HeapMetricsSelector
+
+  val backend = context.actorOf(
+    ClusterRouterGroup(
+      AdaptiveLoadBalancingGroup(HeapMetricsSelector),
+      ClusterRouterGroupSettings(
+        totalInstances = 100, routeesPaths = List("/user/factorialBackend"),
+        allowLocalRoutees = true, useRole = Some("backend"))).props(),
+    name = "factorialBackendRouter2")
+  //#router-lookup-in-code
+}
+
+// not used, only for documentation
+abstract class FactorialFrontend3 extends Actor {
+  //#router-deploy-in-code
+  import akka.cluster.routing.ClusterRouterPool
+  import akka.cluster.routing.ClusterRouterPoolSettings
+  import akka.cluster.metrics.AdaptiveLoadBalancingPool
+  import akka.cluster.metrics.SystemLoadAverageMetricsSelector
+
+  val backend = context.actorOf(
+    ClusterRouterPool(AdaptiveLoadBalancingPool(
+      SystemLoadAverageMetricsSelector), ClusterRouterPoolSettings(
+      totalInstances = 100, maxInstancesPerNode = 3,
+      allowLocalRoutees = false, useRole = Some("backend"))).props(Props[FactorialBackend]),
+    name = "factorialBackendRouter3")
+  //#router-deploy-in-code
+}