seredkin / game-of-three

a basic distributed app of two remote players exchanging int values

Build

Clone the Git repo, check out the default develop branch. The build the solution with Maven:

$ mvn clean install

Some maven build and test messages should end with

[INFO] BUILD SUCCESS

Then locate the largest jar file in the target directory $ cd target $ ls -lh

.. 18M Jul 30 13:42 game-of-three-0.0.1-SNAPSHOT.jar ..

Run

When in the target folder, run the player1 app in the terminal:

$ java -jar -Dspring.profiles.active=player1 game-of-three-0.0.1-SNAPSHOT.jar

Then open the second terminal (Cmd+T) and run the player2 app:

java -jar -Dspring.profiles.active=player2 game-of-three-0.0.1-SNAPSHOT.jar

Use web browser, curl console command or 'Postman'-like client to check the output of endpoints:

1. Play the game with a given first move value (sync endpoint): 'http://localhost:10001/player1/play/56'
2. Play the game with a given first move value (async endpoint): 'http://localhost:10001/player1/async/play/56'

Game Workflow

The player in role player1 always starts the game with a given or random int value in the range (0, Integer.MAX_VALUE-1). To use the random first move value, do not specify any value when initiating the game.

Example of the first move with the maximum possible value 0x7ffffffe:

  {
    "gameId": "6f109d4c-9ab3-4cf4-b047-3d2c3f4eec6d",
    "created": "2018-07-28T16:02:42.898",
    "eventId": "89e85051-452d-4ffc-ac1c-bfa59a2b06e4",
    "previousEventId": "EMPTY",
    "previousMoveValue": 0,
    "player": "PLAYER_1",
    "type": "START_GAME",
    "moveValue": 2147483646
  }

Players make sequential moves by modifying the opponents value within the range [-1, 1], dividing it by three and passing it to the opponent:

  {
    "gameId": "6f109d4c-9ab3-4cf4-b047-3d2c3f4eec6d",
    "created": "2018-07-28T16:02:43.022",
    "eventId": "0ba032cb-61eb-4b5e-96a8-0a216cee9f68",
    "previousEventId": "89e85051-452d-4ffc-ac1c-bfa59a2b06e4",
    "previousMoveValue": 2147483646,
    "player": "PLAYER_2",
    "type": "NEXT_MOVE",
    "moveValue": 715827882
  },
    {
      "gameId": "6f109d4c-9ab3-4cf4-b047-3d2c3f4eec6d",
      "created": "2018-07-28T16:02:43.053",
      "eventId": "6f626fec-9862-4d67-8105-1da0338dbe5b",
      "previousEventId": "0ba032cb-61eb-4b5e-96a8-0a216cee9f68",
      "previousMoveValue": 715827882,
      "player": "PLAYER_1",
      "type": "NEXT_MOVE",
      "moveValue": 238609294
    },

The one who gets the value 1 after its operation, is the winner. The END_GAME event instance has the player value of the winner and moveValue:1.

  {
    "gameId": "a2f0dd5b-5f36-421e-bd71-3c57dc2f0efa",
    "created": "2018-07-30T14:02:53.275",
    "eventId": "179b78d6-3978-457b-80e1-f4fe565c1180",
    "previousEventId": "318a9197-6f79-41e9-b9ae-ea4ad68be545",
    "previousMoveValue": 2,
    "player": "PLAYER_1",
    "type": "END_GAME",
    "moveValue": 1
  }

To play the game with maximum possible initial value: 'http://localhost:10001/player1/play/0xffffffe' which corresponds to Integer.MAX_VALUE-1

Available endpoints

Next move for all roles

Both application profiles 'player1' and 'player2' provide the POST endpoints to make the next move, receiving GameEvent POJO as JSON: 'http://$host:$port/$role'

Role player1

In addition to the basic 'next move' endpoints, two endpoints available: for making the first move and for playing the game in the automatic mode: GET 'http://localhost:10001/player1/start/44' - returns the GameEvent of START_GAME type with the given value GET 'http://localhost:10001/player1/start' - same as previous but with random move value

Remotely-managed workflow

Th GameEvent entity is the single communication element between the services. The first move's entity can be produced by calling an endpoint described in the 'Role player1' section.

Then remote client can produce its one move and post it to an appropriate player by using 'http://$host:$port/$role' template. The return value should be passed to the opponent.

When producing GameEvent instances remotely make sure to preserve consistent game identifier, player and event type information and move values.

Local development environment

As the application shares the codebase, there's an option to run all services on the same host which is convenient for development and integration testing purposes. Just run the app with both profiles specified:

java -jar -Dspring.profiles.active=player1,player2 game-of-three-0.0.1-SNAPSHOT.jar

and then use port 10002 for all communications.

Running on separate hosts

When launching the 'player1' service, override the property -Dopponent.host=http://player-2-host:10002

To override both service's running ports use standard Springs property -Dserver.port=any-int-val

Potential improvements and TODOs

1. Replace Random UUIDs with time-based UUIDs to make sure the sequential nature of the workflow.
2. Add Secure Hash field to ensure the consistency of communicated values.
3. Replace RestTemplate with KafkaTemplate to enforce async communication between services in the automatic play mode.