Asp.Net Core 3 正常关机抛出 OperationCanceledException [英] Asp.Net Core 3 graceful shutdown throws OperationCanceledException

问题描述

我正在尝试正常终止 ASP.Net Core 3.1 服务(将在 Kubernetes 中运行).当 Kubernetes 停止服务时，它会向应用程序发送一个 SIGTERM 事件，此时我希望在终止之前完成正在进行的请求(这可能需要几秒钟)...我想我可以在托管服务中捕获它，如下面，因此不会立即停止.

I'm trying to gracefully terminate a ASP.Net Core 3.1 service (which will run in Kubernetes). When Kubernetes stops a service, it will send a SIGTERM event to the application, at which point I want in-flight requests to complete (which may take several seconds) before terminating... I think I can catch this in a hostedservice, as below, and hence not stop immediately.

以下有效，但超时 5 秒或更长时间，我收到 OperationCanceledException.任何人都可以解释为什么我会收到 OperationCanceledException 或者如何解释延迟 SIGTERM 事件以允许正常关闭的替代方法?

The following works, but with a timeout of 5 seconds or longer, I receive an OperationCanceledException. Could anyone shed any light on why I get an OperationCanceledException or how shed any light on an alternative way to delay a SIGTERM event, to allow a graceful shutdown?

    public static int Main(string[] args)
    {
        var logger = NLogBuilder
            .ConfigureNLog("nlog.config")
            .GetCurrentClassLogger();
        try
        {
            CreateHostBuilder(args)
                .ConfigureServices((hostBuilderContext, services) => { services.AddHostedService<LifetimeEventsHostedService>(); })
                .Build()
                .Run();

            return 0;
        }
        catch (Exception e)
        {
            logger.Fatal(e, "Stopping due to exception");

            return -1;
        }
        finally
        {
            LogManager.Shutdown();
        }
    }

这是托管服务...

    internal class LifetimeEventsHostedService : IHostedService
    {
        private readonly Microsoft.Extensions.Logging.ILogger _logger;
        private readonly IHostApplicationLifetime _appLifetime;

        public LifetimeEventsHostedService(
            ILogger<LifetimeEventsHostedService> logger,
            IHostApplicationLifetime appLifetime)
        {
            _logger = logger;
            _appLifetime = appLifetime;
        }

        public Task StartAsync(CancellationToken cancellationToken)
        {
            _appLifetime.ApplicationStarted.Register(OnStarted);
            _appLifetime.ApplicationStopping.Register(OnStopping);
            _appLifetime.ApplicationStopped.Register(OnStopped);

            return Task.CompletedTask;
        }

        public Task StopAsync(CancellationToken cancellationToken)
        {
            return Task.CompletedTask;
        }

        private void OnStarted()
        {
            _logger.LogInformation("OnStarted has been called.");

            // Perform post-startup activities here
        }

        private void OnStopping()
        {
            _logger.LogInformation("OnStopping has been called.");
            // Perform on-stopping activities here


            // This works, but a timeout of 5 seconds or more subsequently causes an OperationCanceledException
            Thread.Sleep(5000);
        }

        private void OnStopped()
        {
            _logger.LogInformation("OnStopped has been called.");

            // Perform post-stopped activities here
        }
    }

推荐答案

我对使用 ASP.Net Core 3.1 优雅关闭的替代方法持开放态度，就目前而言，我使用的是托管服务.

I'm open to alternative approaches to graceful shutdown with ASP.Net Core 3.1, as it stands, I'm using a hosted service.

在 .Net Core 应用程序中，我设置了 网络主机上的关闭超时，但是，设置通用主机上的ShutdownTimeout 确实允许我在关闭前优雅地等待几秒钟(超过默认的sigterm，即5 秒).@PmanAce 的提示帮助我解决了这个问题.

Within the .Net Core app, I was setting ShutdownTimeout on the webhost, however, setting the ShutdownTimeout on the generic host, does allow me to gracefully wait a number of seconds (more than the default sigterm, which is 5 seconds) prior to shutdown. The hint from @PmanAce helped me work that out.

因此，以下代码允许我优雅地终止.一个警告，LifetimeEventsHostedService 中的 Thread.Sleep 必须小于 option.ShutdownTimeout.

As such, the following codes allow me to gracefully terminate. One caveat, the Thread.Sleep in LifetimeEventsHostedService must be less than option.ShutdownTimeout.

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

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureServices((hostBuilderContext, services) =>
            {
                services.AddHostedService<LifetimeEventsHostedService>();
                services.Configure<HostOptions>(option =>
                {
                    option.ShutdownTimeout = TimeSpan.FromSeconds(30);
                });
            })
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseKestrel();
                webBuilder.UseStartup<Startup>();
            });
}

以下 LifetimeEventsHostedService

The following LifetimeEventsHostedService

public class LifetimeEventsHostedService : IHostedService
{
    private readonly IHostApplicationLifetime _hostApplicationLifetime;

    public LifetimeEventsHostedService(IHostApplicationLifetime hostApplicationLifetime)
    {
        _hostApplicationLifetime = hostApplicationLifetime;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _hostApplicationLifetime.ApplicationStarted.Register(OnStarted);
        _hostApplicationLifetime.ApplicationStopping.Register(OnStopping);
        _hostApplicationLifetime.ApplicationStopped.Register(OnStopped);

        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        return Task.CompletedTask;
    }

    private void OnStopped()
    {
        Console.WriteLine("OnStopped");
    }

    private void OnStopping()
    {
        Console.WriteLine("OnStopping");
        Console.WriteLine(DateTime.Now.ToLongTimeString());

        Thread.Sleep(15000);
        Console.WriteLine("Sleep finished");
        Console.WriteLine(DateTime.Now.ToLongTimeString());
    }

    private void OnStarted()
    {
        Console.WriteLine("OnStarted");
    }
}

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