Booking-Microservices-Sample

Booking Microservices is a Sample application for booking ticket. This application based on different software architecture and technologies like .Net Core, CQRS, DDD, Vertical Slice Architecture, Docker, kubernetes, tye, MassTransit, RabbitMQ, gRPC, yarp reverse proxy, Identity Server, Redis, SqlServer, Entity Framework Core, Event Sourcing and different level of testing.

🌀 This repository is a work in progress and will be completed over time 🚀

Table of Contents

• The Goals of This Project
• Plan
• Technologies - Libraries
• The Domain and Bounded Context - Service Boundary
• Structure of Project
• Prerequisites
• How to Run
  • Docker Compose
  • Kubernetes
• Support
• Contribution

The Goals of This Project

• Microservices based on Domain Driven Design (DDD) implementation.
• Correct separation of bounded contexts for each microservice.
• Communication between bounded contexts through asynchronous MessageBus and events.
• Simple CQRS implementation and event driven architecture.
• Using Best Practice and New Technologies and Design Patterns.
• Using Docker-Compose and Kubernetes for our deployment mechanism.
• Implementing various types of testing like Unit Testing, Integration Testing.

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
API Gateway	Completed ✔️
Identity Service	Completed ✔️
Flight Service	Completed ✔️
Passenger Service	Completed ✔️
Booking Service	Completed ✔️
Building Blocks	In Progress 👷‍♂️

Technologies - Libraries

• ✔️ .NET 6 - .NET Framework and .NET Core, including ASP.NET and ASP.NET Core
• ✔️ MVC Versioning API - Set of libraries which add service API versioning to ASP.NET Web API, OData with ASP.NET Web API, and ASP.NET Core
• ✔️ EF Core - Modern object-database mapper for .NET. It supports LINQ queries, change tracking, updates, and schema migrations
• ✔️ Masstransit - Distributed Application Framework for .NET.
• ✔️ MediatR - Simple, unambitious mediator implementation in .NET.
• ✔️ FluentValidation - Popular .NET validation library for building strongly-typed validation rules
• ✔️ Swagger & Swagger UI - Swagger tools for documenting API's built on ASP.NET Core
• ✔️ Serilog - Simple .NET logging with fully-structured events
• ✔️ Polly - Polly is a .NET resilience and transient-fault-handling library that allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, and Fallback in a fluent and thread-safe manner
• ✔️ Scrutor - Assembly scanning and decoration extensions for Microsoft.Extensions.DependencyInjection
• ✔️ Opentelemetry-dotnet - The OpenTelemetry .NET Client
• ✔️ DuendeSoftware IdentityServer - The most flexible and standards-compliant OpenID Connect and OAuth 2.x framework for ASP.NET Core
• ✔️ EasyCaching - Open source caching library that contains basic usages and some advanced usages of caching which can help us to handle caching more easier.
• ✔️ Mapster - Convention-based object-object mapper in .NET.
• ✔️ Hellang.Middleware.ProblemDetails - A middleware for handling exception in .Net Core
• ✔️ IdGen - Twitter Snowflake-alike ID generator for .Net
• ✔️ Yarp - Reverse proxy toolkit for building fast proxy servers in .NET
• ✔️ Tye - Developer tool that makes developing, testing, and deploying microservices and distributed applications easier
• ✔️ MagicOnion - gRPC based HTTP/2 RPC Streaming Framework for .NET, .NET Core and Unity.
• ✔️ EventStore - The open-source, functional database with Complex Event Processing.
• ✔️ MongoDB.Driver - .NET Driver for MongoDB.
• ✔️ xUnit.net - A free, open source, community-focused unit testing tool for the .NET Framework.
• ✔️ Respawn - Respawn is a small utility to help in resetting test databases to a clean state.

The Domain And Bounded Context - Service Boundary

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

I used yarp reverse proxy to route synchronous and asynchronous requests to the corresponding microservice. 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 (IdentityServer) 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 MassTransit 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 Run

Config Certificate

Run the following commands for Config SSL in your system

dotnet dev-certs https -ep %USERPROFILE%\.aspnet\https\aspnetapp.pfx -p {password here}
dotnet dev-certs https --trust

Note: for running this command in powershell use $env:USERPROFILE instead of %USERPROFILE%

Docker Compose

Run this app in docker using the docker-compose.yaml file with the below command at the root of the application:

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

Documentation Apis

Each microservice uses swagger open api, navigate to /swagger for a list of every endpoint. For testing apis I used the REST Client plugin for VSCode running this file booking.rest.

Support

If you like my work, feel free to:

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

Thanks a bunch for supporting me!

Contribution

Contributions are always welcome! Please take a look at the contribution guidelines pages first.

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.

Project References & Credits

• https://github.com/jbogard/ContosoUniversityDotNetCore-Pages
• https://github.com/kgrzybek/modular-monolith-with-ddd
• https://github.com/oskardudycz/EventSourcing.NetCore
• https://github.com/thangchung/clean-architecture-dotnet
• https://github.com/jasontaylordev/CleanArchitecture
• https://github.com/pdevito3/MessageBusTestingInMemHarness
• https://github.com/devmentors/FeedR

License

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