.Net Core :: Slow first response

1.txt

$curl -o /dev/null -s -w %{time_total}\\n https://localhost:5001
0.470427

$curl -o /dev/null -s -w %{time_total}\\n https://localhost:5001
0.034931

$curl -o /dev/null -s -w %{time_total}\\n https://localhost:5001
0.037043

2.txt

# Start server

$dotnet dist/test.dll
info: Microsoft.Hosting.Lifetime[0]
      Now listening on: http://localhost:5000
info: Microsoft.Hosting.Lifetime[0]
      Now listening on: https://localhost:5001
      
info: Application.WarmupServices[0]
      Starting IHostedService...
      
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]

# Result

$curl -o /dev/null -s -w %{time_total}\\n https://localhost:5001
0.040194

$curl -o /dev/null -s -w %{time_total}\\n https://localhost:5001
0.035138

$curl -o /dev/null -s -w %{time_total}\\n https://localhost:5001
0.028956

Program.cs

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            })
        .ConfigureServices(
            services => services.AddHostedService<WarmupServices>());

}

WarmupServices.cs

public class WarmupServices : IHostedService, IDisposable
{
    private readonly ILogger _logger;
    private readonly HttpClient httpClient;

    public WarmupServices(ILogger<WarmupServices> logger)
    {
        _logger = logger;
        httpClient = new HttpClient();
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("Starting IHostedService...");

        httpClient.GetAsync("<Endpoint URL>");

        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("StoppingIHostedService...");
        return Task.CompletedTask;
    }

    public void Dispose()
    {
        httpClient?.Dispose();
    }
}

Beautiful

simple but effective