Akka Cluster Sharding example

Introduction

This is a Scala Sbt Akka Cluster project that demonstrates how to setup Akka Cluster Sharding on the example of the sea battle game server.

This project builds up to examples of

• Event Sourcing
  
• Command query responsibility segregation (CQRS)
  
• Akka Persistence.

The project has the load test in the following GitHub repo sea-battle-load-test

Compile

$ sbt compile

Test

$ sbt test

Deploy

This script runs MySQL database server and apps in containers :

• node1 with API route and shards
• node2 with shards

$ ./build_deploy_local.sh

Applications will start and see each other the cluster will start successfully

- Cluster Node [akka://ActorSystem@node2:2552] - Welcome from [akka://ActorSystem@node1:2551]
- Member is Up: akka://ActorSystem@node1:2551
- Member is Joined: akka://ActorSystem@node2:2552
- Member is Up: akka://ActorSystem@node2:2552

Akka Event Sourcing Actors uses a database to store events and snapshots, during application startup we will see in the log

- Database initialized successfully

If the application failed to connect to the database server, we will see the corresponding message and reason in the log

- An error occurred while initializing the database: ...

Test manualy

You can call GRPC API methods manualy with grpcurl util. By default, API port is 8080.

grpcurl \ 
-d '{"player1": {"id": "4e0453ee-c7ba-11ec-9d64-0242ac120002"}, "player2": {"id": "541042b6-c7ba-11ec-9d64-0242ac120002"}}' 
-plaintext \
-import-path /home/capdev/Projects/sea-battle/src/main/protobuf \
-proto battle.proto \
localhost:8080 battle.BattleService/start

Add node

if you want more secondary nodes with shards, you need add :

  node3:
    build: .
    environment:
      - ARTERY_HOST=node3
      - SEED1_HOST=node1
      - SEED1_PORT=2551
      - SEED2_HOST=node2
      - SEED2_PORT=2552
      - DB_HOST=mysql