反复启动和停止工作者服务 修改1 编辑2更新

如何解决反复启动和停止工作者服务 修改1 编辑2更新

此项目中有两个文件，program.cs用于操作服务，而worker.cs包含服务逻辑。 在program.cs内部，我使用以下方法操作服务：

// program.cs (partially)
public static void Main(string[] args)
{
    while (true)
    {
        string a = client.ReceiveFrameString();  // To receive a flag from external programs to start the service
        if (bool.Parse(a))
        {
            Console.WriteLine("START");
            Thread t = new Thread(new ParameterizedThreadStart(ThreadProc));
            t.Start(args);
            CreateHostBuilder(args).Build().RunAsync().Wait(); // This works at the first start
            // ATTENTION! CreateHostBuilder(args).Build().Run() will return an error about args.Length < 0
            Console.WriteLine("DONE Start");
        }
    }
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureServices((hostContext,services) =>
                {
                    services.AddHostedService<Worker>();
                });
public static void ThreadProc(object obj)
{
    string[] args = ToStringArray(obj);
    while (true)
    {
        string temp = recv.ReceiveFrameString();  // To receive a flag from external programs to stop the service
        if (!bool.Parse(temp))
        {
            Console.WriteLine("STOP");
            CreateHostBuilder(args).Build().StopAsync().Wait();
            Console.WriteLine("DONE Stop");
            break;  // Jump out of the loop as soon as the service is stopped.
        }
    }
}

如您所见，我正在使用一个while循环来创建一个“ Start-Stop”集，其中包含启动服务的命令和一个从外部源触发时停止服务的线程。我可以根据如下BackgroundService类中被覆盖的StartAsync和StopAsync方法中的日志输出观察服务是否已成功启动和停止：

// worker.cs (partially)
public override async Task StartAsync(CancellationToken cancellationToken)
{
    _logger.Loginformation("STARTED!!");
    await base.StartAsync(cancellationToken);
}
public override async Task StopAsync(CancellationToken cancellationToken)
{
    _logger.Loginformation("STOPPED!!");
    await base.StopAsync(cancellationToken);
}

现在，启动服务的命令在第一次触发时起作用，但是在成功调用线程后，StopAsync无法按预期方式起作用。

作为预期结果，我希望该服务能够反复启动和停止。那有什么问题呢？并且有解决方案吗？

修改1

最小可重复的示例是located here.

编辑2（更新）

经过几天关于堆栈溢出和MSDN的研究，我终于找到了适用于我的方案的解决方案。

首先，根据this answer，我确定我的应用程序不是长期服务，因此我删除了Worker中的“ repeat-until-your-BackgroundService-is-stopped”循环服务模板：

// From worker.cs
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
    // Remove the while loop
    /*while (!stoppingToken.IsCancellationRequested)
    {
        // _logger.Loginformation("Worker running at: {time}",DateTimeOffset.Now);
        // await Task.Delay(1000,stoppingToken);
    }*/
}

第二，根据this MSDN C# API about RunAsync(IHost,CancellationToken)，我可以创建一个CancellationSource，它可以生成CancellationToken来取消它。与the example given in the documentation类似，我可以通过取消源关闭工作程序。因此，实现变为：

// From program.cs
public static void Main(string[] args)
{
    while (true)
    {
        string a = client.ReceiveFrameString();  // To receive a flag from external programs to start the service
        if (bool.Parse(a))
        {
            Console.WriteLine("START");
            CancellationTokenSource source = new CancellationTokenSource();
            CancellationToken token = source.Token;
            Thread t = new Thread(new ParameterizedThreadStart(ThreadProc));
            t.Start(source);
            CreateHostBuilder(args).Build().RunAsync(token);
            Console.WriteLine("DONE Start");
        }
    }
}
public static void ThreadProc(object obj)
{
    var source = obj as CancellationTokenSource;
    while (true)
    {
        string temp = recv.ReceiveFrameString();  // To receive a flag from external programs to stop the service
        if (!bool.Parse(temp))
        {
            Console.WriteLine("STOP");
            source.Cancel();
            source.dispose();
            Console.WriteLine("DONE Stop");
            break;  // Jump out of the loop as soon as the service is stopped.
        }
    }
}

但是，此解决方案不适用于带有“重复直到您的BackgroundService已停止”循环的工作人员。似乎CancellationToken无法触发worker.cs中ExecuteAsync内部的取消请求。现在应该问这个问题：如何使用“重复-直到您的BackgroundService-is-stopped”循环启动和停止辅助服务？ The original Minimal Producible Example was adjusted according to the EDIT 2 now.