BackgroundService 未关闭，stoppingToken 从未使用 .net core 通用主机设置

Question

我有一个在.net通用主机中托管的BackgroundService，如下所示：

var builder = Host.CreateDefaultBuilder(args);

builder
    .ConfigureLogging((hostingContext, logging) =>
    {
        logging.ClearProviders();
        logging.AddConsole();
        if(hostingContext.HostingEnvironment.IsDevelopment() == true)
            logging.AddDebug();
    })
    .ConfigureHostConfiguration(configurationBuilder =>
    {
        configurationBuilder.AddCommandLine(args);
    })
    .ConfigureAppConfiguration((hostingContext, configApp) =>
    {
        var env = hostingContext.HostingEnvironment;
        Console.WriteLine(env.EnvironmentName);
    })
    .UseConsoleLifetime();

然后我就有了我的工人：

public class Worker : BackgroundService
{
    private readonly ILogger<Worker> _logger;

    public Worker(ILogger<Worker> logger)
    {
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        // here i am doing something with ClientWebSocket, threads etc
        // snipped for brevity. I want to avoid spinning in a loop

        // the debugger reaches the following line
        WaitHandle.WaitAny(new[] { stoppingToken.WaitHandle });

        // but never hits this line
        this.logger.LogInformation("shutting down worker");
    }
}

在运行应用程序的 Windows 终端上按 ctrl+c 时，它会显示

Application is shutting down

（这是来自框架），但是 movingToken 永远不会被设置（所以我无法关闭我的工作线程）。

stoppingToken 如何以及何时设置，以及如何优雅地终止我的工作人员？

控制台

Answer 1

对于后台服务，它们需要继续运行，直到取消令牌指示停止。为此，您需要一个 while 循环。但是，当您将此取消令牌传递到任何异步方法时，如果您在所有层中使用相同的令牌，它将阻止该方法在整个链中运行。它应该看起来像这样：

  protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            // here i am doing something with ClientWebSocket, threads etc
            // snipped for brevity. I want to avoid spinning in a loop
            ... 
            await client.DownloadAsync(..., stoppingToken);
            ...
        }

        // but never hits this line
        this.logger.LogInformation("shutting down worker");
    }

Answer 2

你可以这样做：

await Task.Delay(TimeSpan.FromMinutes(10), stoppingToken);