NetCoreMediatrSample

Sample using Command and Query Responsibility Segregation (CQRS) implemented in .NET Core by using MediatR and using background workers, real-time metrics and monitoring, logging, validations and more

Some of the dependencies are:

• App.Metrics: Real time metrics and monitoring set up with InfluxDb and Grafana.
• AutoFixture: Auto generate test objects.
• AutoMapper: Eliminate a lot of boilerplate by auto mapping objects (eg. request and response).
• CorrelationId: Add Correlation ID to Http context to easier track errors.
• FluentAssertions: Better and easier assertions in tests.
• FluentValidation: Validating requests before they are handled.
• Hangfire: Background worker.
• MediatR: Dispatching request/response, commands, queries, notifications and events.
• Microsoft.EntityFrameworkCore: Object-relational mapping.
• Microsoft.Extensions.Logging: Logging API that allow other providers.
• Moq: Mocking framework used for testing.
• StructureMap: IoC Container.
• Xunit: Testing framework.

Running on .NET Core 2.1

Structure

• Src: Source of the application.
• DataModel: Models for the database/store.
• Test: Application tests (right now only unit tests).

Src

Src is structured by having each feature in a single file. That gives the following structure:

• Controllers: All the controllers with endpoints exposed.
• Features: All features (eg. User/GetUser.cs).
• Infrastructure: Infrastructure for the application it self (eg. Middlewares, Filters, Pipeline).
• ThirdParty: Third party services (eg. Facebook login).

Setting up application

The application require 2 databases - one for the application it self and one for Hangfire.

1. Create a new appsettings to your ASPNETCORE_ENVIRONMENT (eg appsettings.Development.json) and add the 2 new connection strings for application and Hangfire.
2. Run database changes to the application database by running the command dotnet ef database update -s ../Src inside DataModel folder (see commands in DataModel/DatabaseContext.cs).

Setting up real time metrics

Real time metrics require Grafana and InfluxDb.

1. Add InfluxDb options to appsettings.
2. Download Grafana dashboard here.

Logging

Logging is set up with Microsoft.Extensions.Logging which means you can add logging providers by your self to it. As now it is set up as follow:

• Status codes 5xx, that are caused by an exception, are logged as critical.
• Other status codes, that are caused by an exception, are logged as warning.
• The whole pipeline (request to response) is logged as information.

Critical and warning logs are named <endpoint> :: [<status code>] <exception message> and contain request, stacktrace and correlation id.

The user receives error message and correlation id in production. For non-production environments the stacktrace is also included.

Build and run with Docker

$ docker build -t aspnetapp .
$ docker run -d -p 8080:80 --name myapp aspnetapp