c# - 在asp.net core应用程序中实现IHostedService，如何在没有IIS上第一个请求的情况下运行它？

Question

我已经在 asp.net core 网站中实现了 IHostedService。它工作得很好，但问题是我希望它在托管服务器启动或 IIS 服务重新启动时启动，但除非收到对网站的第一个请求，否则它不会启动。

• 该网站托管在 IIS 版本 10.0.18 上
• AppPool 处于“AlwaysRunning”模式
• “PreloadEnabled”在网站上为“True”。
• 将“.NET CLR 版本”设置为“无托管代码”或“v4.0.xxxxxx”没有帮助。
• dotnet core 版本为 2.2，并且已安装 dotnet core 托管 bundle 。

更新1:@Arthur 建议的“应用程序初始化模块”没有帮助。既不在站点级别，也不在服务器级别。

我使用的配置:

    <applicationInitialization
         doAppInitAfterRestart="true"
         skipManagedModules="false"
         remapManagedRequestsTo="init.htm">
        <add initializationPage="/init.htm" hostName="localhost"/>
    </applicationInitialization>

更新2:这是我实现界面的方式

internal class PaymentQueueService : IHostedService, IDisposable
{
    private readonly ILogger _logService;
    private Timer _timerEnqueue;

    public PaymentQueueService(ILogger logService)
    {
        _logService = logService;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _logService.LogInformation("Starting processing payments.");

        _timerEnqueue = new Timer(EnqueuePayments, null, TimeSpan.Zero,
            TimeSpan.FromSeconds(10));

        return Task.CompletedTask;
    }

    private void EnqueuePayments(object state)
    {
        _logService.LogInformation("Enqueueing Payments.");
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        _logService.LogInformation("Stopping processing payments.");

        _timerEnqueue?.Change(Timeout.Infinite, 0);

        return Task.CompletedTask;
    }

    public void Dispose()
    {
        _timerEnqueue?.Dispose();
    }
}

main.cs 文件中的 Program 类:

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

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args).ConfigureServices(services =>
            {
                services.AddHostedService<PaymentQueueService>();
            }).Configure((IApplicationBuilder app) =>
            {

                app.UseMvc();
            })
                .UseStartup<Startup>();
    }

启动类:

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {

        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostEnvironment env)
        {

        }
    }

Answer 1

由于建议的“应用程序初始化模块”不起作用，您可以考虑自己与客户进行通话

The module starts the process for the ASP.NET Core app when the first request arrives and restarts the app if it shuts down or crashes.

public class Program {
    static Lazy<HttpClient> client = new Lazy<HttpClient>();
    public static async Task Main(string[] args) {
        var host = CreateWebHostBuilder(args).Start();//non blocking start
        using (host) {
            bool started = false;
            do {
                var response = await client.Value.GetAsync("site root");
                started = response.IsSuccessStatusCode;
                await Task.Delay(someDelayHere);
            } while (!started);
            
            host.WaitForShutdown();
        }
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureServices(services => {
                services.AddHostedService<PaymentQueueService>();
            })
            .Configure((IApplicationBuilder app) => {
                app.UseMvc();
            })
            .UseStartup<Startup>();
}

注意:

To prevent apps hosted out-of-process from timing out, use either of the following approaches:

• Ping the app from an external service in order to keep it running.
• If the app only hosts background services, avoid IIS hosting and use a Windows Service to host the ASP.NET Core app.