Configure options for the ASP.NET Core Kestrel web server

In the world of .NET Core development, there’s a superhero called Kestrel. It’s like the guardian of our web applications, handling all the incoming requests. But, to make it work the way we want, we need to configure it. In this guide, we’ll explore how to set up Kestrel in simple terms, covering the basics, making things secure with HTTPS, and diving into some cool features.

Getting Started: Basic Kestrel Setup

To begin, we tell Kestrel which door to use (like the entrance of a building). In our code, it looks like this:

`.ConfigureWebHostDefaults(webBuilder =>
{
    webBuilder.UseKestrel(options =>
    {
        options.Listen(IPAddress.Any, 5000);
    })
    .UseContentRoot(Directory.GetCurrentDirectory())
    .UseStartup<Startup>();
})

This says, “Hey Kestrel, listen to requests on any available door (IP address) on port 5000.”

Staying Secure with HTTPS

Security is crucial. To make our application use a secure connection (HTTPS), we tell Kestrel to use a special certificate:

.ConfigureWebHostDefaults(webBuilder =>
{
    webBuilder.UseKestrel(options =>
    {
        options.Listen(IPAddress.Any, 5000);
        options.Listen(IPAddress.Any, 5001, listenOptions =>
        {
            listenOptions.UseHttps("path/to/certificate.pfx", "certificatePassword");
        });
    })
    .UseContentRoot(Directory.GetCurrentDirectory())
    .UseStartup<Startup>();
})

This says, “Kestrel, listen on port 5001 too, but this time, use this special certificate for secure connections.”

Fine-Tuning with Advanced Configuration

For those who want to tweak things a bit more, there’s a way to customize how Kestrel behaves. We can adjust settings like how many people it can handle at once or how big a request it can handle:

.ConfigureWebHostDefaults(webBuilder =>
{
    webBuilder.UseKestrel(options =>
    {
        options.Limits.MaxConcurrentConnections = 100;
        options.Limits.MaxConcurrentUpgradedConnections = 100;
        options.Limits.MaxRequestBodySize = 10 * 1024; // 10 MB
    })
    .UseContentRoot(Directory.GetCurrentDirectory())
    .UseStartup<Startup>();
})

This says, “Hey Kestrel, let’s handle up to 100 people at the same time, and don’t accept requests larger than 10 MB.”

Thread Pool Configuration

Kestrel has a team of workers (threads) to handle requests efficiently. We can tell it how many team members it should have and how long they can rest:

.ConfigureWebHostDefaults(webBuilder =>
{
    webBuilder.UseKestrel(options =>
    {
        options.ThreadPoolMinCount = 2;
        options.ThreadPoolMaxCount = 100;
        options.ThreadPoolIdleTimeout = TimeSpan.FromMinutes(5);
    })
    .UseContentRoot(Directory.GetCurrentDirectory())
    .UseStartup<Startup>();
})

This says, “Kestrel, you have a team. Make sure there are at least 2 people in the team, but no more than 100. If someone is not busy, let them rest after 5 minutes.”

Reverse Proxies

Sometimes, our application is not directly facing the internet. It’s like having a friend (reverse proxy) answering the door first. We need to tell Kestrel how to deal with this:

.ConfigureWebHostDefaults(webBuilder =>
{
    webBuilder.UseKestrel(options =>
    {
        options.AddServerHeader = false;
        options.ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto;
    })
    .UseContentRoot(Directory.GetCurrentDirectory())
    .UseStartup<Startup>();
})

This says, “Kestrel, if someone asks, pretend you don’t have a name (server header). Also, if a friend (proxy) tells you who’s knocking, believe them.”

Conclusion

Configuring Kestrel might sound complex, but it’s like giving instructions to a friendly guard at the entrance of your app. By understanding these simple settings, you can make your app safer, faster, and work smoothly with the outside world. So, go ahead, explore Kestrel’s powers, and make your .NET Core applications shine!