The goal of this project is the creation of a basic lobby system with a frontend using Godot and a backend server built in Java using the Quarkus framework. For documentation on the the frontend check this repository.
Language: Java 11
Framework: Quarkus
- Java JDK 11+
- Maven 3.8+
- MongoDB Accessible on the internet
- The easiest way I found to do this for free is with Mongodb's Cloud Platform
In order to run locally you will need to create the file src/main/resources/application-local.properties. This file will allow you to modify your properties when running the application locally, the only property that is required is quarkus.mongodb.connection-string in order to allow our server to connect to the database.
Note: The
.gitignorewill ignore this file by default so you should not have to worry about putting in Database Credentials on a public repo, and the line can be removed if you fork this into a private repository
Example application-local.properties:
# Database (REQUIRED)
quarkus.mongodb.connection-string=mongodb+srv://readwrite:[email protected]/game?retryWrites=true&w=majority
# Gives trace level logging for our code making local debugging easier.
quarkus.log.category."org.landister".level=TRACE
# Set Logging Levels
quarkus.log.console.format=%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p [%c] (%t) %s%e%n
quarkus.log.category."org.mongodb.driver".level=WARN
quarkus.log.level=INFOOnce your properties file is in place you can run your application in dev mode using:
mvn compile quarkus:dev -Dquarkus.profile=localOr if you have make installed using:
make startTip: Navigating to
localhost:8080will give you a 404 page with a list of links you can hit that come default with quarkus. Theq/devlink is useful to explore and better understand what the different java beans and build processes created by the code.
Tip: Dev mode includes
live updatesmeaning most code change will take effect without having to recompile (although some changes such as property changes will require a recompile)
Once the server is up and running either locally or on a hosted provider, the Godot Frontend can be connected by modifying the Websocket Host-> Hostname Url as noted here in the Updating Server Host Information section.
There are lots of ways to deploy your application on the interwebs. I have used Google Cloud in the past and you should be able to get that working for free or close too. I think that AWS may also have some free options. But I have recently started playing around with Digital Ocean and I have really like the interface and simplicity of it. The pricing is also very reasonable(not totally free). The rest of this demo assumes you are creating a single instance of the backend server at the lowest price for DO($5 a month). And keep in mind that the app can be deleted and redeployed fairly easily using the Github CI/CD process included with this repo and the rate is pro-rated for when the application is actually up. Meaning you can create an account deploy it play around with it for a couple hours then delete it and it will only cost you like $0.20
Tip: Don't forget to delete the instance :)
The GitHub CI/CD process specified later in this README builds our application as an image that is later deployed into a running container. In order to store this image we need access to an Image Registry.
DigitalOcean offers a way to create a container repository. The free level lets you create a single repo that will hold enough data to house at least one version of our image.
Note: If you have access to a different container registry you would rather use that is fine, but you may need to make some changes to the Gitlab CI/CD Pipeline.
This repository includes a .github/workflows folder that will create a Github Workflow by default. But in order for it to work there are two secrets that will need to be added to your repo's "secrets" which can be done through the setting menu, documented here
Note: You will need to activate your Github Workflows which can be done through the
Actionstab on your repo
Important: Since we are using the
doctlcommand (DO's proprietary CLI) if you want to use a different image repository you will need to modify the CI pipeline to usedockerinstead.
| Name | Value | Example |
|---|---|---|
| DIGITALOCEAN_ACCESS_TOKEN | Token retrieved from the DO cloud ui. API -> Generate New TokenSee Creating Repository Secrets section of the frontend README for more info |
|
| REGISTRY_BASE_URL | Base url retrieved from the Container page. Should probably be registry.digitalocean.com |
registry.digitalocean.com |
| REGISTRY_NAME | Registry name should be the part after the / so if your url looks like registry.digitalocean.com/myrepo it would be myrepo |
myrepo |
| DATABASE_URL | Database Url (should include credentials) IMPORANT: You must escape all of the &s with a \ |
mongodb+srv://readwrite:[email protected]/database?retryWrites=true\&w=majority |
The pipeline associated with pushing the image to the image repository is .github/workflows/deploy-image. This should be done every time you commit to the main branch based on the push section located at line 10. Note that it will only happen if the commit includes a change to the src folder, pom.xml, etc... (assuming workflows were activated). So the easiest way to test this workflow is by just adding a space to the end of the pom.xml and pushing a commit.
The application can be created by running pipeline Create Backend Application on Digital Ocean supplied by the .github/workflows/create-app.yml. Note that the application infrastructure specs are based on the config/digital-ocean/spec.yml file. This file can be customized based on the spec found here
Repository: Make sure to replace the repository information in the spec with your repo info, should just be a name change.
Machine: Defaulting to a single instance of the most basic pod instance (512 mb of memory and 1 shared CPU). it is the cheapest option at $5 a month as of the writing of this README, and can easily be deleted and redeployed using this pipeline again.
Note: If you want to test out your app with more than a your friend(s) you can up your memory and cpu options with a different
slugwhich you can find using thedoctl apps tier instance-size listcommand.
Region: Defaults to your closest region but more regions can be found using the doctl apps list-regions command.
Important: Be careful if you remove the
namefield. Doing so could result in multiple instances of your application being deployed which could result in an unpleasant bill. You should also throw a couple billing alerts on you Digital Ocean instance just to be safe.
The Create Backend Application on Digital Ocean assumes the container repository has already been created and the image has been deployed (see Build Image and Push above for instructions on how to do this). And it also assumes that there is a "latest" tagged image.
The workflow is set in a way that it needs to be run manually in order to prevent accidental multiple deployments. More about manual deployments can be found here and an example of running the manual workflow can be found in the frontend README.
After everything is set up navigate to actions in the Github UI and run Create Backend Application in Digital Ocean workflow.
Easiest way to validate your deployment is by using the DO UI. Navigate to cloud.digitalocean.com > Apps and find the application named lobby-example-app-backend.
Find your app's endpoint by hitting the Live Appbutton to get the base URL and then navigate to the path /q/health
Once you have validated your application has been deployed the only thing left is to setup the Frontend End and update the host information to point to your newly deployed server
At this point you should be able to register/login to your server and start a new game.
Below I have tried to document some of the basics of how the application works, and how the code is layed out.
flowchart TD
subgraph gc[Godot Client]
gLogin(Login Scene)
gLobby(Main/Game Lobby Scene)
gGame(InGame Scene)
end
subgraph qs[Quarkus Server]
qLogin(Login Controller)
qLobby(Lobby Controller)
qGame(Game Controller)
cache[(In-Memory Cache)]
end
db[(MongoDB Database)]
gLogin --1. Check Credentials--> qLogin
qLogin -- 2. Retrieve User Info --> db
qLogin --3. Send JWT Token--> gLogin
gLogin -- 4. User Logged In --> gLobby
qLobby -- Store/Retrieve Lobby Info --> cache
gLobby -- "5. Retrieve Game List/Game Lobby Info" --> qLobby
gLobby -- "6. Start Game" --> gGame
gGame -- "7. Get Game Info" --> qGame
qGame -- Store/Retrieve Game Info --> cache
style gc fill:#0B8384,stroke:#333,stroke-width:4px
style qs fill:#EE0000,stroke:#333,stroke-width:4px
style db fill:#4DB33D,stroke:#333,stroke-width:4px
Tip: While this repo is a single code base that contains the controllers for the Login/Lobby/InGame. There is no reason it could not be deployed separately as a Login Server, Lobby Server, and set of In Game Servers. Which is how I would probably want to do it in a production environment.
Tip: The "In-Memory" cache is just a java object in this implementation meaning a reboot wipes out your cache, and multiple servers don't share the same cache. But I would probably make it a Redis Server or similar technology if I had more time.
📦src
┣ 📂main
┃ ┣ 📂java.org.landister.lobby.backend
┃ ┃ ┣ 📂mapper ➊
┃ ┃ ┣ 📂model❷
┃ ┃ ┃ ┣ 📂dao Ⓐ
┃ ┃ ┃ ┣ 📂enums Ⓑ
┃ ┃ ┃ ┣ 📂request Ⓒ
┃ ┃ ┃ ┣ 📂response Ⓒ
┃ ┃ ┃ ┣ 📂session Ⓓ
┃ ┃ ┃ ┗ 📂shared Ⓔ
┃ ┃ ┣ 📂services
┃ ┃ ┣ 📂util
┃ ┃ ┗ 📂websocket❸
┃ ┃ ┃ ┣ 📂games
┃ ┃ ┃ ┃ ┗ 📜WalkingSimulator.java Ⓔ
┃ ┃ ┃ ┣ 📜BaseController.java Ⓐ
┃ ┃ ┃ ┣ 📜ChatController.java Ⓑ
┃ ┃ ┃ ┣ 📜LobbyController.java Ⓒ
┃ ┃ ┃ ┗ 📜LoginController.java Ⓓ
┃ ┗ 📂resources
┃ ┃ ┗ 📜application.properties
┣ 📜LICENSE
┣ 📜Makefile ❹
┣ 📜README.md
┣ 📜pom.xml
- mappers: A set of Mappers used to translate to/from a DTO(Data Transfer Object) to a Request or Response
- model: POJOs representing different pieces of the application
- A. Database Objects
- B. Shared enums used across our model
- C. request: Client to Server request/ response: Server to Client responses
- D. Used to save user information for in-memory cache
- E. Inner objects shared across our model
- websocket: WebSocket Connection Controllers
- A. BaseController: Controller that is extended by all the other Websocket Controllers (except login). This is where our common logic lives
- B. ChatController: Extended by controllers that use the chat functionality. Contains logic for sending messages to specific users and all users in a game
- C. LobbyController: Controller backing the initial login screen
- D. LoginController: Controller backing the main lobby, and game lobby screen
- E. WalkingSimulator: Controller backing our example game
- MakeFile Utilizes make to run commands
Communication from the frontend to the backend happen using WebSockets. With the data being passed using the JSON Format for the most part. This provides an easier way for both our client and server to pass and interpret multiple pieces of information at once.
When a user logins to our application we will retrieve that users info and return back a JWT that will be used for validation and will contain the user's username information. And the Godot client will store that token as a cookie for future use. See the BaseControler for the validation logic.
Note: The JWT has a 5 hour expiration by default and currently has no logic for automatic refresh.
If we are able to successfully login, we will check to see if the user is currently in a an in-progress game and put them there if so. Or if not we will put the user in the main lobby and refresh the list of active games.
sequenceDiagram
participant Client as User's Godot Client
participant Controller as Quarkus Server
participant Database as Database
note right of Client: User Enters login info and hit's "LOGIN"
Client->>+Controller: Get: { requestType: LOGIN }
Database->>Controller: Retrieve User Info
Controller->>-Client: Send: <JWT Token>
Client->>Client: Save token in Cookie
Client->>Client: Load Lobby View
critical Send Initial Request from User
Client->>+Controller: Get: { requestType: INITIAL_REQUEST }
Database->>Controller: Retrieve User's Game Data
Controller->>Client: Send: { type: load_assets }
option No Game Data Found for User
Controller->>Client: Send: { type: leave_game }
Client->>Controller: Get: { requestType: REFRESH_LOBBY }
Controller->>Client: Send: { type: game_list, game: <Open Game's Info> }
Client->>Client: Update Game List with Open Games
option User is Currently In-Game
Controller->>Client: Send: { type: join_game }
Client->>Client: Load Game View
end
The host of a game lobby in which a valid number of players have joined, has the option of starting the game. Once started a message will be sent to all the clients in the game and they will load the "In Game Scene". From there the server will request that the host decide on the spawn points and send that info back to the server, where the server will relay that information to the rest of the clients currently in the game.
Note: I am not going to go over the "restart" logic but it works effectively the same way.
sequenceDiagram
participant UClient as Host Godot Client
participant GClient as Peer's Godot Clients
participant Controller as Quarkus Server
participant Database as Database
note right of UClient: Host hits "START" from Game Lobby
rect rgb(191, 223, 255)
note right of UClient: Lobby Controller
UClient->>+Controller: Request: { requestType: START_GAME }
Controller->>UClient: Response: { type: start_game }
Controller->>GClient: Response: { type: start_game }
end
UClient-->>UClient: Load Game Scene
GClient-->>GClient: Load Game Scene
rect rgb(225, 225, 153)
note right of UClient: InGame Controller
UClient->>+Controller: Request: { requestType: INITIAL_REQUEST }
Controller-->>Controller: Validate Request is from Host
Database-->>Controller: Retrieve Game Info
Controller->>UClient: Response: { type: load_assets }
UClient-->>UClient: "Load Player/Goal Spawn Points"
UClient->>+Controller: Request: { requestType: LOAD_ASSETS, <Spawn Point Info> }
Controller-->>Database: Update Game Info
Controller->>GClient: Response: { type: map_setup, player: <Player Location>, goal: <Goal Spawn> }
GClient->>GClient: Update scene
Controller->>UClient: Response: { type: map_setup, player: <Player Location>, goal: <Goal Spawn> }
UClient->>UClient: Update scene
end
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