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Nest Logo HANGMAN

Description

project to learn about DDD and Event Sourcing

in a Docker setup using Eventstore

Goal : Have a complete template application for a Domain Driven/ Event Sourced backend using NestJS.

ToDo / Done

  • Setup NestJS architecture
  • API controller and GraphQL resolver use the games.service for mutation and query
  • Setup CQRS Game domain: commands, commandhandlers, call aggregate methods, applying events to aggregate, catching event in eventhandler
  • dockerize project, app + projections container
  • setup projection-db with typeorm: eventhandlers update projection
  • service has methods using typeorm that return the results from the projections-db
  • Build eventstore module with custom publisher, custom eventbus, and reading from/ writing to EventstoreDB using evenstore client. Learned a lot about NestJS dependency injection
  • extract new module into npm library
  • aggregate's applied events are stored in eventstoredb
  • eventstore module is subscribed to eventstore stream and adds new events to the NestJS cqrs EventBus (meaning it will end up in the EventHandlers)
  • added ViewEventBus to the eventstore module, including writing a custom ViewUpdater decorator. Any class decorated with this decorator (typing enforces it needs a handle method) will get registered in the ViewUpdaters. Any event published onto the ViewEventBus will look for the matching registered updater class, and will call it's handle method
  • added ViewUpdater classes that update the projection to the application. Decorated with @ViewUpdaterHandler(EventClass) it will handle the event coming from EventstoreDB
  • implement multiple aggregates/ streams possibility into the nestjs-eventstoredb library

sept 2022

  • NestJS new setup working latest version
  • better filestructure
  • GQL working
  • Games domain working via CQRS
  • Dockerize the project
  • Eventstore setup working
  • Add Users domain (Aggregate with createNew method, commands, cmdhandlers, events, eventhandlers, viewupdaterhandlers)
  • TypeORM setup working
  • Updaters are updating projections
  • TypeORM migrations
  • Merge updateDependencies branch to master
  • using latest dependencies versions complete, merge updateDependencies branch to master
  • store last processed event checkpoint, on app init only replay from checkpoint (read checkpoint from stream)
  • update dependencies
  • include config in repo instead of .env for easier sharing and running of project
  • replay events: dangerous admin thing only anyway, so just remove position entries from mongodb and restart app
  • Add Auth module
  • add docker build in github checks
  • cache-manager to store username:userId pairs in memory
  • createUser check username doesn't exist
  • [won't do, node.js not the right tool for this] store aggregate in cache and keep updated on changes. So the aggregate doesnt have to be built up from all events when the aggregate is needed
  • Add User to Game
  • Change user info flow incl update all (both at this point) projections
  • Support multiple updaters for one event (each domain can have it's own updater for the same event) lib change
  • eventstore lib: Fix uncaught in promise on game-id not found
  • Try again revive aggregate from json
  • Use Redis for cache
  • use internal repository for aggregates (will only work within the single node process. Fallback to redis, then fallback to replay from events)
  • Swap projection database type for mongodb
  • Store last read position for each projection. Able to add a new projection and rebuild only that one (not overwrite the others)
  • add snapshot functionality to eventstore library
  • Implement actual hangman logic. Goal: backend is ready for comm with frontend
  • Setup websocket server
  • fix typeorm migration:generate in correct folder
  • ...

Frontend:

  • setup hangman app in this dockerized project
  • add user login and start new game UI (pick wordToGuess from randomized public api)
  • setup websocket client: connect to server on login, receive init message in redux middleware, mutate state (after making guess, the backend sends the so far rightly guessed characters on the correct positions)
  • [ ]

Known issues

  • when working on the npm package, npm link to test out the latest version of the package without publishing makes NestJS clash. something with peer dependencies?

Installation

prepare .env file for environment variables with content:

(for testing purposes, .env is included in the repository)

DIR_DATA_PATH="$PWD"
CONTAINER_COMMAND="npm run start"
CONTAINER_SCALE="1"
APP_PORT=5050
CONTAINER_PORT=4000
EVENTSTORE_CLUSTER_SIZE=1
EVENTSTORE_RUN_PROJECTIONS=All
EVENTSTORE_START_STANDARD_PROJECTIONS=true
EVENTSTORE_EXT_TCP_PORT=1113
EVENTSTORE_EXT_HTTP_PORT=2113
EVENTSTORE_INSECURE=true
EVENTSTORE_ENABLE_EXTERNAL_TCP=true
EVENTSTORE_ENABLE_ATOM_PUB_OVER_HTTP=true
EVENT_STORE_HOSTNAME=hangman-eventstore
PROJECTIONS_HOSTNAME=hangman-projections
PROJECTIONS_PORT=3310
PROJECTIONS_CREDENTIALS_USERNAME=root
PROJECTIONS_CREDENTIALS_PASSWORD=example
PROJECTIONS_DB_TYPE=mysql
PROJECTIONS_DATABASE=hangman-projections
STORE_STATE_DB_TYPE=mongodb
STORE_STATE_HOSTNAME=hangman-position
STORE_STATE_PORT=27017
STORE_STATE_USERNAME=root
STORE_STATE_PASSWORD=example
STORE_STATE_DB=hangman-position
MONGO_PROJECTIONS_HOSTNAME=127.0.0.1
MONGO_PROJECTIONS_PORT=27017
MONGO_PROJECTIONS_CREDENTIALS_USERNAME=root
MONGO_PROJECTIONS_CREDENTIALS_PASSWORD=example
MONGO_PROJECTIONS_DB_TYPE=mongodb
MONGO_PROJECTIONS_DATABASE=hangman-projections-mongo
GQL_PLAYGROUND=enabled
JWT_SECRET=test
EXPIRES_IN=1h

Migrations

Will be run on start of the container

To run manually:

$ docker-compose exec hangman-ddd-events npm run migration:run

# after adding model(s) or make changes to models, generate new migration:
$ docker-compose exec hangman-ddd-events npm run migration:generate -- [migration-name]
$ docker-compose build

Running the app

# development
$ docker-compose up

Interfaces

Test

# unit tests
$ npm run test

# e2e tests
$ npm run test:e2e

# test coverage
$ npm run test:cov