Started on guide page

akka-edge-docs/src/main/paradox/guide.md

@@ -18,7 +18,8 @@ the local center to pick up available orders closest to their location.
 2. [Coarse Grained Location Replication](guide/2-drone-location-to-cloud-service.md)
 3. [Restaurant Deliveries Service](guide/3-restaurant-deliveries-service.md)
 4. [Local Drone Delivery Selection](guide/4-local-drone-delivery-selection.md)
-5. [Deploying the Services](guide/5-deploying-the-services.md)
+5. [Drone Charging Station](guide/5-charging-station.md)
+6. [Deploying the Services](guide/6-deploying-the-services.md)
 
 @@@
 

akka-edge-docs/src/main/paradox/guide/5-charging-station.md

@@ -0,0 +1,32 @@
+# Drone Charging Station
+
+To showcase active-active replication between edge and cloud we'll now add a @extref[Replicated Event Sourced Entity](akka-projection:grpc-replicated-event-sourcing-transport.html)
+in the form of a charging station. The charging stations are created with a location id placing them in one of the 
+local-drone-control edge services where the entity is replicated. Drones in that location can request to charge in the
+charging station, and be charged if there is a free charging slot.
+
+## Charging station entity
+
+The API for creating a replicated event sourced behavior extends the regular event sourced behavior. It accepts three
+different commands from the outside `Create` to initialize a charging station, `StartCharging` to start a charging session
+for a drone if possible and `GetState` to query the station for its current state. There is also a private `ChargingCompleted`
+command that the entity can send to itself.
+
+The `Create` command leads to a `Created` event which is persisted and initialized the charging station.
+
+When a slot is free and a drone requests charging a `ChargingStarted` event is persisted and once charging a drone has
+completed a `ChargingCompleted` event is persisted:
+
+Scala
+:  @@snip [ChargingStation.scala](/samples/grpc/local-drone-control-scala/src/main/scala/charging/ChargingStation.scala) { #commands #events }
+
+Java
+:  @@snip [ChargingStation.java](/samples/grpc/local-drone-control-java/src/main/java/charging/ChargingStation.java) { #commands #events }
+
+
+
+The charging station is a simplified replicated entity in that it doesn't really expect any possible conflicts, stations
+are created in the central cloud and replicated to the edge, updates related to drones currently charging in the station
+happen at the edge and are replicated to the cloud. Akka replicated event sourcing provides APIs for both CRDTs where
+conflicts are automatically handled by the data structure and business domain level conflict resolution. For more details 
+about see the @extref[Akka documentation](akka:replicated-eventsourcing.html).

samples/grpc/local-drone-control-java/src/main/java/charging/ChargingStation.java

@@ -28,7 +28,7 @@ public class ChargingStation
     extends ReplicatedEventSourcedBehavior<
         ChargingStation.Command, ChargingStation.Event, ChargingStation.State> {
 
-  // commands and replies
+  // #commands
   public interface Command extends CborSerializable {}
 
   public static final class Create implements Command {
@@ -81,8 +81,9 @@ public CompleteCharging(String droneId) {
       this.droneId = droneId;
     }
   }
+  // #commands
 
-  // events
+  // #events
   public interface Event extends CborSerializable {}
 
   public static final class Created implements Event {
@@ -125,7 +126,7 @@ public ChargingDrone(String droneId, Instant chargingDone, String replicaId) {
       this.replicaId = replicaId;
     }
   }
-
+  // #events
   public static final class State implements CborSerializable {
     public final int chargingSlots;
     public final Set<ChargingDrone> dronesCharging;

samples/grpc/local-drone-control-scala/src/main/scala/charging/ChargingStation.scala

@@ -32,7 +32,7 @@ import scala.math.Ordered.orderingToOrdered
 
 object ChargingStation {
 
-  // commands and replies
+  // #commands
   sealed trait Command extends CborSerializable {}
   case class Create(
       locationId: String,
@@ -51,15 +51,17 @@ object ChargingStation {
       extends Command
 
   private case class CompleteCharging(droneId: String) extends Command
+  // #commands
 
-  // events
+  // #events
   sealed trait Event extends CborSerializable {}
   case class Created(locationId: String, chargingSlots: Int) extends Event
   case class ChargingStarted(droneId: String, chargeComplete: Instant)
       extends Event
       with StartChargingResponse
 
   case class ChargingCompleted(droneId: String) extends Event
+  // #events
 
   case class ChargingDrone(
       droneId: String,