如何在.NET核中通过cron作业实现后台任务调度

Question

我希望根据每个请求创建一个动态的cron作业(如果应用服务器关机，不应该影响后台任务)，并且可以重新安排或删除cron作业。如何在.NET核心中实现这一点？

Answer 1

创建一个新的.NET核心控制台应用程序，并在主方法(使用C# 7)内的Program.cs中使用以下模板：

public static async Task Main(string[] args)
{  
    var builder = new HostBuilder()
        .ConfigureAppConfiguration((hostingContext, config) =>
        {
        // i needed the input argument for command line, you can use it or simply remove this block
            config.AddEnvironmentVariables();

            if (args != null)
            {
                config.AddCommandLine(args);
            }

            Shared.Configuration = config.Build();
        })
        .ConfigureServices((hostContext, services) =>
        {
            // dependency injection
      
            services.AddOptions();
           // here is the core, where you inject the
           services.AddSingleton<Daemon>();
           services.AddSingleton<IHostedService, MyService>();
        })
        .ConfigureLogging((hostingContext, logging) => {
           // console logging 
            logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
            logging.AddConsole();
        });

    await builder.RunConsoleAsync();
}

下面是守护进程/服务代码

public class MyService: IHostedService, IDisposable
   {
       private readonly ILogger _logger;
       private readonly Daemon _deamon;

       public MyService(ILogger<MyService> logger, Daemon daemon /* and probably the rest of dependencies*/)
       {
           _logger = logger;         
           _daemon = daemon;  
       }

       public async Task StartAsync(CancellationToken cancellationToken)
       {
           await _deamon.StartAsync(cancellationToken);
       }

       public async Task StopAsync(CancellationToken cancellationToken)
       {
           await _deamon.StopAsync(cancellationToken);
       }

       public void Dispose()
       {
           _deamon.Dispose();
       }
}

下面是您想要做的核心，下面的代码是一个模板，您必须提供正确的实现

public class Daemon: IDisposable
   {
       private ILogger<Daemon> _logger;
        
      
       protected TaskRunnerBase(ILogger<Daemon> logger)
       {
          _logger = logger;
       }
        
       public async Task StartAsync(CancellationToken cancellationToken)
       {            
           while (!cancellationToken.IsCancellationRequested)
           {
                await MainAction.DoAsync(cancellationToken); // main job 
            }
       }

       public async Task StopAsync(CancellationToken cancellationToken)
       {
           await Task.WhenAny(MainAction, Task.Delay(-1, cancellationToken));
           cancellationToken.ThrowIfCancellationRequested();
       }

       public void Dispose()
       {
            MainAction.Dispose();
       }
}

1. 您可以在Windows和Linux上运行它，因为您使用的是.NET核心
2. 我的.NET核心版本是2.1。