asp.net core: What is the best practice to execute code in a container application for kubernetes

Question

I created a container application for kube.netes project pattern. I want to run there a service that listens to messages and do work in an endless loop. I execute it from Configure method Startup.cs . From some references this is the place to do so. Before that i register all services to ConfigureServices method like a normal asp.net app. Also, I want to use IApplicationLifetime.ApplicationStopping to be triggered. I didn't find a way to achieve both things: execute the code of the task listener and controlling the callback of ApplicationStopping. this is my Configure method

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            var cancellationToken = new CancellationTokenSource();
            var tasksListener = app.ApplicationServices.GetRequiredService<ITaskListener>();
            var appLifetime = app.ApplicationServices.GetRequiredService<IApplicationLifetime>();
            appLifetime.ApplicationStopping.Register(() =>
            {
                Console.WriteLine("ApplicationStopping is stopping");
            });
            tasksListener.Listen(cancellationToken.Token).Wait();
            app.Run(async (context) =>
            {
                await tasksListener.Listen(cancellationToken.Token);
            });
        }

I'm able to stop the application and see the print, but the code inside app.Run isn't executed. If I switch this code:

            app.Run(async (context) =>
            {
                await tasksListener.Listen(cancellationToken.Token);
            });

with this:

                tasksListener.Listen(cancellationToken.Token).Wait();

so the code is executed but then IApplicationLifetime.ApplicationStopping won't be executed. Any idea?

Answer 1

for those who encounter same problem I'll update that the solution for me was simply delete Startup.cs and do everything from Program.cs , so it will look like this

    public class Program
    {
        public static void Main(string[] args)
        {
            IWorker worker = new Worker();
            CancellationTokenSource cancellationToken = new CancellationTokenSource();
            CreateWebHostBuilder(args, worker, cancellationToken).Build().RunAsync();
            worker.Work(cancellationToken.Token).Wait();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args, IWorker worker, CancellationTokenSource cancellationToken) =>
            WebHost.CreateDefaultBuilder(args)
            .Configure((app) =>
            {
                var appLifetime = app.ApplicationServices.GetRequiredService<IApplicationLifetime>();
                appLifetime.GracefullyTerminate(worker, cancellationToken);
            });
    }

what i found out is that Startup.cs fit to implement app service that get calls from outside. app.Run refer to what will happen when a request will come.

In addition, microsoft launched in .net core 3.0 a Worker Service project template that fit exactly to this purpose. you can find reference here https://learn.microsoft.com/en-us/as.net/core/fundamentals/host/hosted-services?view=as.netcore-3.1&tabs=visual-studio