Chat

Description

Proof of concept of a scalable microservice architecture using DDD / CQRS / Repository pattern

Tech Stack: Nestjs, Typescript, Redis, gRPC, Socket.io, Nx, Pm2, RabbitMQ, MongoDB

Intallation

yarn install
yarn global pm2 @nrwl/cli

docker run -d -p 6379:6379 redis

yarn start:build-all
yarn start:prod-all

Usage

After creating user, create chat room by using the username of the receiver as a route param. i.e. /chat/user1

Architecture

• Client: using socket.io to communicate with the gateway
• Gateway: using gRPC to connect to the Chat Service
• Chat Service: using Redis as in-memory for storage only and connects through rabbitmq to Chat History Service for permanent storage
• Chat History Service: permanent storage using mongodb (or elasticsearch at some point)

Chat Service

• application
  • commands
  • controllers
  • events
  • queries
  • sagas
• domain
  • entities
  • contracts
• infrastucture
  • repositories

Chat History Service

Client Structure

• core: configuration files for the 3rd party libs (apollo client, etc)
• components: react components. each component is structred as: components/index/styles
• pages: represents application pages. each page is independent from each other and is structed like a component. (also includes routes)
• store: state managment related files:
  • redux:
    • actions
    • reducers
    • middleware
    • effects
    • selectors
    • types
  • apollo:
    • containers
    • selectors
• services: api calls, graphql queries/mutations
• utils
• constants
• context: hocs and context api
• hooks

DDD approach

• core: configuration files for the 3rd party libs (apollo client, etc)
• component lib: react components. each component is structred as: components/index/styles
  • atoms
  • molecules
  • organisms (error handers etc)
• components: same as component lib, but for app specific components and
  • organisms
• store: global state managment related files:
  • redux:
    • actions
    • reducers
    • middleware
    • effects
    • selectors
    • types
  • apollo:
    • containers
    • selectors
• services: api calls, graphql queries/mutations
• utils: shared utils
• constants: shared constants
• context: hocs and context api
• hooks: shared hooks
• modules: in most cases represents application pages, also contains an app module which contains app logic (routes, themes, appbar). each page is independent from each other
  • home
    • store: state managment related files:
      • redux:
        • actions
        • reducers
        • middleware
        • effects
        • selectors
        • types
      • apollo:
        • containers
        • selectors
    • services: api calls, graphql queries/mutations
    • utils
    • constants
    • context: hocs and context api
    • hooks
    • componentes: organisms, layouts are in component folder
    • Component.ts: page is in top level
    • index.ts
  • routes.tsx
  • index.ts

NOTE: everything in top level (shared components, hooks, utils) must be well documented using storybook, jsdoc

NOTE: store, services, utils, constants, context, hooks can be split into shared lib if they are not app specific

NOTE: for component development follow atomic design for exmplanation atomic design

Contract Lib

Library containing contract interfaces from each service

Proto Lib

Library containing proto files and ts interfaces for grpc

Resources

• Tackle Business Complexity in a Microservice with DDD and CQRS Patterns
• Clean Architecture Talk by Jason Taylor
• Exploring CQRS and Event Sourcing
• Nestjs gRPC
• Nestjs CQRS
• Building Microservices: Using Node.js with DDD, CQRS, and Event Sourcing