🚀 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 Sourcing, CQRS, DDD, gRpc, MongoDB, RabbitMq, Masstransit in .Net 8.

💡 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, Event Sourcing, CQRS, DDD and gRpc.

Table of Contents

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

The Goals of This Project

• ❇️ Using Vertical Slice Architecture for architecture level.
• ❇️ Using Domain Driven Design (DDD) to implement all business processes in microservices.
• ❇️ Using Rabbitmq on top of Masstransit for Event Driven Architecture between our microservices.
• ❇️ Using gRPC for internal communication between our microservices.
• ❇️ Using CQRS implementation with MediatR library.
• ❇️ Using Postgres for write side of some microservices.
• ❇️ Using MongoDB for read side of some microservices.
• ❇️ Using Event Store for write side of Booking-Microservice to store all historical state of aggregate.
• ❇️ 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.
• ❇️ Using Unit Testing for testing small units and mocking our dependencies with Nsubstitute.
• ❇️ Using End-To-End Testing and Integration Testing for testing features with all dependencies using testcontainers.
• ❇️ Using Fluent Validation and a Validation Pipeline Behaviour on top of MediatR.
• ❇️ Using Minimal API for all endpoints.
• ❇️ Using Health Check for reporting the health of app infrastructure components.
• ❇️ Using Docker-Compose and Kubernetes for our deployment mechanism.
• ❇️ Using Kibana on top of Serilog for logging.
• ❇️ Using OpenTelemetry for distributed tracing on top of Jaeger.
• ❇️ Using OpenTelemetry for monitoring on top of Prometheus and Grafana.
• ❇️ Using IdentityServer for authentication and authorization base on OpenID-Connect and OAuth2.
• ❇️ Using Yarp as a microservices gateway.
• ❇️ Using Kubernetes to achieve efficient scaling and ensure high availability for each of our microservices.
• ❇️ Using Nginx Ingress Controller for load balancing between our microservices top of Kubernetes.
• ❇️ Using cert-manager to Configure TLS in kubernetes cluster.

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	Completed ✔️

Technologies - Libraries

• ✔️ .NET 7 - .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
• ✔️ NewId - NewId can be used as an embedded unique ID generator that produces 128 bit (16 bytes) sequential IDs
• ✔️ 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
• ✔️ gRPC-dotnet - gRPC functionality for .NET.
• ✔️ 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.
• ✔️ Testcontainers - Testcontainers for .NET is a library to support tests with throwaway instances of Docker containers.
• ✔️ K6 - Modern load testing for developers and testers in the DevOps era.

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.

After saving data in write side, I save a Internal Command record in my Persist Messages storage (like something we do in outbox pattern) and after committing transaction in write side, trigger our command handler in read side and this handler could save their read models in our MongoDB database.

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 to Config SSL in your system:

Windows using Linux containers

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

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

macOS or Linux

dotnet dev-certs https -ep ${HOME}/.aspnet/https/aspnetapp.pfx -p $CREDENTIAL_PLACEHOLDER$
dotnet dev-certs https --trust

Docker Compose

To run this app in Docker, use the docker-compose.yaml and execute the below command at the root of the application:

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

Kubernetes

To configure TLS in the Kubernetes cluster, we need to install cert-manager based on the docs and run the following commands to apply TLS in our application. Here, we use Let's Encrypt to encrypt our certificate.

kubectl apply -f ./deployments/kubernetes/booking-cert-manager.yml

To apply all necessary deployments, pods, services, ingress, and config maps, please run the following command:

kubectl apply -f ./deployments/kubernetes/booking-microservices.yml

Build

To build all microservices, run this command in the root of the project:

dotnet build

Run

To run each microservice, run this command in the root of the Api folder of each microservice where the csproj file is located:

dotnet run

Test

To test all microservices, run this command in the root of the project:

dotnet 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/kgrzybek/modular-monolith-with-ddd
• https://github.com/oskardudycz/EventSourcing.NetCore
• https://github.com/thangchung/clean-architecture-dotnet
• https://github.com/pdevito3/MessageBusTestingInMemHarness

License

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