c# - Setup RabbitMQ consumer in ASP.NET Core application

Question

I have an ASP.NET Core application where I would like to consume RabbitMQ messages.

I have successfully set up the publishers and consumers in command line applications, but I'm not sure how to set it up properly in a web application.

I was thinking of initializing it in Startup.cs, but of course it dies once startup is complete.

How to initialize the consumer in a the right way from a web app?

Answer 1

Use the Singleton pattern for a consumer/listener to preserve it while the application is running. Use the IApplicationLifetime interface to start/stop the consumer on the application start/stop.

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<RabbitListener>();
    }


    public void Configure(IApplicationBuilder app)
    {
        app.UseRabbitListener();
    }
}

public static class ApplicationBuilderExtentions
{
    //the simplest way to store a single long-living object, just for example.
    private static RabbitListener _listener { get; set; }

    public static IApplicationBuilder UseRabbitListener(this IApplicationBuilder app)
    {
        _listener = app.ApplicationServices.GetService<RabbitListener>();

        var lifetime = app.ApplicationServices.GetService<IApplicationLifetime>();

        lifetime.ApplicationStarted.Register(OnStarted);

        //press Ctrl+C to reproduce if your app runs in Kestrel as a console app
        lifetime.ApplicationStopping.Register(OnStopping);

        return app;
    }

    private static void OnStarted()
    {
        _listener.Register();
    }

    private static void OnStopping()
    {
        _listener.Deregister();    
    }
}

• You should take care of where your app is hosted. For example, IIS can recycle and stop your code from running.
• This pattern can be extended to a pool of listeners.