Europa Overview

A sample dotnet core 2.0 application demonstrating messaging, CQRS and microservices.

Architecture

• Web: ASP.NET Core MVC
• Micro-services: CQRS Style commands and queries

Write Service

• Writes are made to a Postgres database
• Dapper is used for sql execution
• In a master-slave arrangement these changes would be written to the master

Query Service

• Reads are made against postgres database views
• Dapper is used for sql execution
• In a master-slave arrangement these reads would be made against the slave

Search Service

• In response to events occuring, a Solr search index is updated.
• In response to queries, Solr is searched and its results returned.

Feed Service

• Handles podcast feed retrieval / refreshes.

Messaging Infrastructure

• Messages are defined as

  • IEvent: Raised to commicate that an event has occurred within the domain.
  • ICommand: Send to change somthing in the domain.
  • IQuery: Requested to retrieve information about the domain

• Dispatchers dispatch messages to the rabbit bus

  • ICommandDispatcher, IQueryDispatcher and IEventDispatcher

• Executors execute a message that has been received.

  • Starting a new scope
  • Resolving the appropriate handler
  • Executing the handler by passing in the message to be handled.

Other Infrastructure

• Database maintenance performed using FluentMigrator
• Message validation performed using FluentValidation
• Unit of Work implementation to perform multiple Dapper Sql operations in the context of a transaction.
• Unit testing using xUnit, Fluent Assertions and Moq.

Nuget Packages Used

• Messaging
  • EasyNetQ
  • RabbitMQ
• Infrastructure
  • Autofac
  • Autofac.Extensions.DependencyInjection
  • Dapper
  • Dapper.SimpleCRUD.NetCore
  • FluentMigrator
  • FluentMigrator.Runner
  • Npgsql
• Testing
  • FubarDev.NDbUnit.Core
  • FubarDev.NDbUnit.Postgresql
  • FluentAssertions
  • FluentAssertions.AspNetCore.Mvc
  • Moq
• Web
  • AutoMapper
  • FluentValidation.AspNetCore

Instructions for running

Run Application via docker compose

docker-compose up --build

Run Tests via docker compose

docker-compose -f docker-compose.test.yml up --build --abort-on-container-exit

Stop and remove all containers

docker stop $(docker ps -a -q)
docker rm $(docker ps -a -q)

Related Links

• Download .NET Core 2 https://www.microsoft.com/net/download/core
• DockerHub images
  • https://hub.docker.com/r/microsoft/dotnet/
  • https://hub.docker.com/r/microsoft/aspnetcore/
• Related Blog Posts
  • http://udidahan.com/2009/12/09/clarified-cqrs/
  • https://martinfowler.com/bliki/CQRS.html