docs: Sample of edge initiated replicated event sourcing (#1083)

.github/workflows/checks.yml

@@ -200,3 +200,12 @@ jobs:
         run: |-
           cd samples/grpc/iot-service-scala
           sbt test -Dakka-projection.version=`cat ~/.version`
+
+      - name: gRPC sample Java charger RES identical impl check
+        run: |-
+          diff samples/grpc/local-drone-control-java/src/main/java/charging/ChargingStation.java samples/grpc/restaurant-drone-deliveries-service-java/src/main/java/charging/ChargingStation.java
+
+      - name: gRPC sample Scala charger RES identical impl check
+        run: |-
+          # RES sample should be identical
+          diff samples/grpc/local-drone-control-scala/src/main/scala/charging/ChargingStation.scala samples/grpc/restaurant-drone-deliveries-service-scala/src/main/scala/charging/ChargingStation.scala

samples/grpc/local-drone-control-java/README.md

@@ -47,6 +47,19 @@ Inspect the current state of the local delivery queue
 grpcurl -plaintext 127.0.0.1:8080 local.drones.DeliveriesQueueService.GetCurrentQueue
 ```
 
+Ask to charge the drone, with a charging station first created in the restaurant-drone-deliveries service:
+
+```shell
+grpcurl -d '{"drone_id":"drone1","charging_station_id":"station1"}' -plaintext 127.0.0.1:8080 local.drones.DroneService.GoCharge
+```
+
+Use the restaurant-drone-deliveries charge station inspection command to see the charging drones, and that they eventually
+complete their charging:
+
+```shell
+grpcurl -d '{"charging_station_id":"station1"}' -plaintext localhost:8101 charging.ChargingStationService.GetChargingStationState
+```
+
 ## Running the sample as a multi node service
 
 It is also possible to run this sample service as a multi node Akka Cluster, for that you need to start a PostgreSQL

samples/grpc/local-drone-control-java/pom.xml

@@ -22,13 +22,14 @@
         <akka-persistence-r2dbc.version>1.2.0</akka-persistence-r2dbc.version>
         <akka-management.version>1.5.0</akka-management.version>
         <akka-diagnostics.version>2.1.0</akka-diagnostics.version>
-        <akka-http.version>10.5.1</akka-http.version>
+        <akka-http.version>10.6.0</akka-http.version>
         <akka-grpc.version>2.4.0</akka-grpc.version>
         <akka-grpc-maven-plugin.version>2.4.0</akka-grpc-maven-plugin.version>
         <logback.version>1.2.13</logback.version>
         <prometheus.client.version>0.16.0</prometheus.client.version>
         <junit.version>4.13.1</junit.version>
         <scala.binary.version>2.13</scala.binary.version>
+        <protobuf-java.version>3.22.2</protobuf-java.version>
         <native.maven.plugin.version>0.9.26</native.maven.plugin.version>
         <mainClass>local.drones.Main</mainClass>
         <!-- needs to be defined to allow for overriding through mvn exec:exec -DAPP_CONFIG=local1.conf -->
@@ -166,6 +167,13 @@
             <version>${logback.version}</version>
         </dependency>
 
+        <!-- for using predefined protobuf message types, see also maven dependency plugin config below -->
+        <dependency>
+            <groupId>com.google.protobuf</groupId>
+            <artifactId>protobuf-java</artifactId>
+            <version>${protobuf-java.version}</version>
+        </dependency>
+
         <!-- Prometheus client for custom metrics -->
         <dependency>
             <groupId>io.prometheus</groupId>
@@ -244,12 +252,54 @@
                 </configuration>
             </plugin>
 
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>getClasspathFilenames</id>
+                        <goals>
+                            <!-- provides the jars of the classpath as properties inside of maven
+                                 so that we can refer to one of the jars in the exec plugin config below -->
+                            <goal>properties</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>unpack</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>unpack</goal>
+                        </goals>
+                        <configuration>
+                            <artifactItems>
+                                <artifactItem>
+                                    <groupId>com.google.protobuf</groupId>
+                                    <artifactId>protobuf-java</artifactId>
+                                    <version>${protobuf-java.version}</version>
+                                    <type>jar</type>
+                                    <overWrite>true</overWrite>
+                                    <outputDirectory>${project.build.directory}/proto</outputDirectory>
+                                    <includes>**/*.proto</includes>
+                                </artifactItem>
+                            </artifactItems>
+                            <overWriteReleases>false</overWriteReleases>
+                            <overWriteSnapshots>true</overWriteSnapshots>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+
             <plugin>
                 <groupId>com.lightbend.akka.grpc</groupId>
                 <artifactId>akka-grpc-maven-plugin</artifactId>
                 <version>${akka-grpc-maven-plugin.version}</version>
                 <configuration>
                     <language>Java</language>
+                    <protoPaths>
+                        <!-- include predefined google protobuf message types -->
+                        <protoPath>target/proto</protoPath>
+                        <!-- our own protobuf messages and gRPC services -->
+                        <protoPath>src/main/protobuf</protoPath>
+                    </protoPaths>
                 </configuration>
                 <executions>
                     <execution>