c# - BackgroundService 未关闭，stoppedToken 从未使用 .net 核心通用主机设置

Question

我在 .net 通用主机中托管了一个 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();

然后我有我的 worker :

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");
    }
}

在正在运行的应用程序的 Windows 终端的 ctrl+c 上显示 Application is shutting down (这是来自框架)但是停止 token 永远不会被设置(所以我不能关闭我的 worker )。

如何以及何时设置停止 token ，以及如何优雅地终止我的工作人员？

控制台

Answer 1

对于 BackgroundServices，它们需要继续运行，直到取消 token 说停止。为此，您需要一个 while 循环。但是，当您将此取消 token 传递给任何 Async 方法时，如果您在所有层中使用相同的 token ，它将停止该方法在整个链中运行。它应该是这样的:

  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");
    }