A practical and imaginary microservices for implementing an infrastructure for up and running distributed system with the latest technology and architecture like Vertical Slice Architecture, Event Driven Architecture, CQRS, Postgres, RabbitMQ and Nestjs. 🚀

💡 This project is not business-oriented and most of my focus was in the thechnical part for implement a distributed system with a sample project. In this project I implemented some concept in microservices like Messaging, Tracing, Event Driven Architecture, Vertical Slice Architecture, CQRS.

You can find Expressjs ported of this project in this link: 🔗 booking-microservices-expressjs

Table of Contents

• The Goals of This Project
• Plan
• Technologies - Libraries
• The Domain and Bounded Context - Service Boundary
• Structure of Project
• How to Use Migrations
• How to Run
  • Docker-Compose
  • Build
  • Run
  • Test
• Documentation Apis
• Support
• Contribution

The Goals of This Project

• ❇️ Using Vertical Slice Architecture for architecture level.
• ❇️ Using Data Centric Architecture based on CRUD in all Services.
• ❇️ Using Rabbitmq on top of amqp for Event Driven Architecture between our microservices.
• ❇️ Using Rest for internal communication between our microservices with axios.
• ❇️ Using Nestjs for web framework.
• ❇️ Using Nestjs CQRS for implementation of command and query with CommandBus and QueryBus.
• ❇️ Using Nestjs Typeorm for database level with postgres.
• ❇️ Using Nestjs Dependency Injection for handling dependency injection.
• ❇️ Using Nestjs Passport for authentication and authorization, base on JWT.
• ❇️ Using Nestjs Swagger for generate api documentation automatically.
• ❇️ Using Nestjs Logger for logging.
• ❇️ Using OpenTelemetry for distributed tracing top of Jaeger and Zipkin.
• ❇️ Using OpenTelemetry for monitoring top of Prometteuse and Grafana.
• ❇️ Using Joi for validation input in our handlers and endpoints.
• ❇️ Using dotenv for configuration management.
• ❇️ Using Unit Testing for testing small units and mocking our dependencies with Jest.
• ❇️ Using End-To-End Testing and Integration Testing for testing features with all dependencies using testcontainers.
• ❇️ Using ts-mapper for mapping our objects.
• ❇️ Using Problem Details standard for readable details of errors.
• ❇️ Using eslint and prettier for formatting of our code.
• ❇️ Using Docker-Compose for our deployment mechanism.
• 🚧 Using Nestjs MongoDB for read side with mongoose.
• 🚧 Using Domain Driven Design (DDD) to implement all business processes in microservices.
• 🚧 Using Inbox Pattern for ensuring message idempotency for receiver and Exactly once Delivery.
• 🚧 Using Outbox Pattern for ensuring no message is lost and there is at At Least One Delivery.

Plan

🌀This project is a work in progress, new features will be added over time.🌀

I will try to register future goals and additions in the Issues section of this repository.

High-level plan is represented in the table

Feature	Status
Identity Service	Completed ✔️
Flight Service	Completed ✔️
Passenger Service	Completed ✔️
Booking Service	Completed ✔️
Building Blocks	Completed ✔️

Technologies - Libraries

• ✔️ microsoft/TypeScript - TypeScript is a language for application-scale JavaScript.
• ✔️ nestjs/nest - Nest is a framework for building efficient, scalable Node.js server-side applications
• ✔️ nestjs/cqrs - A lightweight CQRS module for Nest framework (node.js)
• ✔️ nestjs/typeorm - TypeORM module for Nest
• ✔️ nestjs/swagger - OpenAPI (Swagger) module for Nest
• ✔️ nestjs/passport - Passport utilities module for Nest
• ✔️ amqp-node/amqplib - A library for making AMQP 0-9-1 clients for Node.JS
• ✔️ open-telemetry/opentelemetry-js - A framework for collecting traces, metrics, and logs from applications
• ✔️ siimon/prom-client - A prometheus client for Node.js that supports histogram, summaries, gauges and counters
• ✔️ axios/axios - Promise based HTTP client for the browser and node.js
• ✔️ motdotla/dotenv - Dotenv is a zero-dependency module that loads environment variables from a .env
• ✔️ PDMLab/http-problem-details - This library implements HTTP Problem details (RFC 7807) for HTTP APIs
• ✔️ hapijs/joi - The most powerful schema description language and data validator for JavaScript
• ✔️ jestjs/jest - A javascript framework for testing
• ✔️ testcontainers/testcontainers-node - A library to support tests with throwaway instances of Docker containers
• ✔️ faker-js/faker - Generate massive amounts of fake (but realistic) data for testing and development
• ✔️ florinn/typemoq - Simple mocking library for JavaScript targeting TypeScript development
• ✔️ ladjs/supertest - High-level abstraction for testing HTTP
• ✔️ eslint/eslint - ESLint is a tool for identifying and reporting on patterns found in ECMAScript/JavaScript code
• ✔️ prettier/prettier - Opinionated Code Formatter
• ✔️ vercel/async-retry - Retrying made simple, easy, and async
• ✔️ MarluanEspiritusanto/ts-mapper - A mapper for mapping one object to another

The Domain And Bounded Context - Service Boundary

• Identity Service: The Identity Service is a bounded context for the authentication and authorization of users using passport. This service is responsible for creating new users and their corresponding roles and permissions using Jwt for authentication and authorization.

• Flight Service: The Flight Service is a bounded context CRUD service to handle flight related operations.

• Passenger Service: The Passenger Service is a bounded context for managing passenger information, tracking activities and subscribing to get notification for out of stock products.

• Booking Service: The Booking Service is a bounded context for managing all operation related to booking ticket.

Structure of Project

In this project I used a mix of clean architecture, vertical slice architecture and I used feature folder structure to structure my files.

Each microservice has its dependencies such as databases, files etc. Each microservice is decoupled from other microservices and developed and deployed separately. Microservices talk to each other with Rest or gRPC for synchronous calls and use RabbitMq or Kafka for asynchronous calls.

We have a separate microservice Identity for authentication and authorization of each request. Once signed-in users are issued a JWT token. This token is used by other microservices to validate the user, read claims and allow access to authorized/role specific endpoints.

I used RabbitMQ as my MessageBroker for async communication between microservices using the eventual consistency mechanism. Each microservice uses amqp to interface with RabbitMQ providing, messaging, availability, reliability, etc.

Microservices are event based which means they can publish and/or subscribe to any events occurring in the setup. By using this approach for communicating between services, each microservice does not need to know about the other services or handle errors occurred in other microservices.

I treat each request as a distinct use case or slice, encapsulating and grouping all concerns from front-end to back. When adding or changing a feature in an application in n-tire architecture, we are typically touching many "layers" in an application. We are changing the user interface, adding fields to models, modifying validation, and so on. Instead of coupling across a layer, we couple vertically along a slice. We minimize coupling between slices, and maximize coupling in a slice.

With this approach, each of our vertical slices can decide for itself how to best fulfill the request. New features only add code, we're not changing shared code and worrying about side effects.

Instead of grouping related action methods in one controller, as found in traditional ASP.net controllers, I used the REPR pattern. Each action gets its own small endpoint, consisting of a route, the action, and an IMediator instance (see MediatR). The request is passed to the IMediator instance, routed through a Mediatr pipeline where custom middleware can log, validate and intercept requests. The request is then handled by a request specific IRequestHandler which performs business logic before returning the result.

The use of the mediator pattern in my controllers creates clean and thin controllers. By separating action logic into individual handlers we support the Single Responsibility Principle and Don't Repeat Yourself principles, this is because traditional controllers tend to become bloated with large action methods and several injected Services only being used by a few methods.

I used CQRS to decompose my features into small parts that makes our application:

• Maximize performance, scalability and simplicity.
• Easy to maintain and add features to. Changes only affect one command or query, avoiding breaking changes or creating side effects.
• It gives us better separation of concerns and cross-cutting concern (with help of mediatr behavior pipelines), instead of bloated service classes doing many things.

Using the CQRS pattern, we cut each business functionality into vertical slices, for each of these slices we group classes (see technical folders structure) specific to that feature together (command, handlers, infrastructure, repository, controllers, etc). In our CQRS pattern each command/query handler is a separate slice. This is where you can reduce coupling between layers. Each handler can be a separated code unit, even copy/pasted. Thanks to that, we can tune down the specific method to not follow general conventions (e.g. use custom SQL query or even different storage). In a traditional layered architecture, when we change the core generic mechanism in one layer, it can impact all methods.

How to Use Migrations

Note: For easy using of migrations commands in typeorm, I add some scripts in package.json and base on these scripts we can use below commands to generate and run migrations easily.

For generating a new migration use this command in the root of each microservice:

npm run migration:generate -- src/data/migrations/new-migration-name

Also for running migration use this command in the root of each microservice:

npm run migration:run  

How to Run

Docker Compose

Use the command below to run our infrastructure with docker using the infrastructure.yaml file at the root of the app:

docker-compose -f ./deployments/docker-compose/infrastructure.yaml up -d

Todo

I will add docker-compsoe for up and running whole app here in the next...

Build

To build each microservice, run this command in the root directory of each microservice where the package.json file is located:

npm run build

Run

To run each microservice, run this command in the root of the microservice where package.json is located:

npm run dev

Test

To test each microservice, run this command in the root directory of the microservice where the package.json file is located:

npm test

Documentation Apis

Each microservice has a Swagger OpenAPI. Browse to /swagger for a list of endpoints.

As part of API testing, I created the booking.rest file which can be run with the REST Client VSCode plugin.

Support

If you like my work, feel free to:

• ⭐ this repository. And we will be happy together :)

Thanks a bunch for supporting me!

Contribution

Thanks to all contributors, you're awesome and this wouldn't be possible without you! The goal is to build a categorized, community-driven collection of very well-known resources.

Please follow this contribution guideline to submit a pull request or create the issue.

Project References & Credits

• https://github.com/jbogard/ContosoUniversityDotNetCore-Pages
• https://github.com/nestjs

License

This project is made available under the MIT license. See LICENSE for details.