在哪里可以記錄 ASP.NET Core 應用程序的啟動/停止/錯誤事件？

Question

在舊的 ASP.NET 中，在Global.asax.cs類中，我會記錄應用程序何時啟動、停止和拋出未處理的異常：

• Application_Start()
• Application_End()
• Application_Error()

我如何在 ASP.NET Core 中做同樣的事情？ 它有一個Startup類，但它用於配置。

我在哪里掛鈎到應用程序的開始/停止/錯誤事件？

Answer 1

您需要使用Microsoft.AspNetCore.Hosting.IApplicationLifetime

    /// <summary>
    /// Triggered when the application host has fully started and is about to wait
    /// for a graceful shutdown.
    /// </summary>
    CancellationToken ApplicationStarted { get; }

    /// <summary>
    /// Triggered when the application host is performing a graceful shutdown.
    /// Requests may still be in flight. Shutdown will block until this event completes.
    /// </summary>
    CancellationToken ApplicationStopping { get; }

    /// <summary>
    /// Triggered when the application host is performing a graceful shutdown.
    /// All requests should be complete at this point. Shutdown will block
    /// until this event completes.
    /// </summary>
    CancellationToken ApplicationStopped { get; }

IApplicationLifetime 的實例可以在Configure方法中獲得。 還要在這里添加 ILoggerFactory：

public void Configure(IApplicationBuilder app, IApplicationLifetime applicationLifetime, ILoggerFactory loggerFactory)
{
    // use applicationLifetime
}

擁有ILoggerFactory ，您可以創建ILogger實例：

var logger = loggerFactory.CreateLogger("StartupLogger"); 

所以你只需要在 Startup 類中創建一個屬性來持久化ILogger的實例（或ILoggerFactory ，如果你想為不同的事件創建不同的 ligger 實例）。 總結一下：

public class Startup 
{
    private ILogger _logger;

    public void Configure(IApplicationBuilder app, IApplicationLifetime applicationLifetime, ILoggerFactory loggerFactory) 
    {
        applicationLifetime.ApplicationStopping.Register(OnShutdown);
        ... 
        // add logger providers
        // loggerFactory.AddConsole()
        ...
        _logger = loggerFactory.CreateLogger("StartupLogger");
    }

    private void OnShutdown()
    {
         // use _logger here;
    }
}

Answer 2

請參閱CaptureStartupErrors和方法.CaptureStartupErrors(true) ，這將有助於你找到問題。

當某些東西在 localhost 上運行完美但在 Azure 中失敗時，這尤其方便。

這是我對 NetCore Web Apps 的常用配置：

public static IWebHost BuildWebHost(string[] args) => WebHost
            .CreateDefaultBuilder(args)
            .CaptureStartupErrors(true)
            .UseKestrel()
            .UseIISIntegration()
            .UseStartup<Startup>()
            .UseAzureAppServices()
            .Build();

在 Azure 應用服務中，您可以在 Kudu 工具的日志流中找到日志https://<appname>.scm.azurewebsites.net/api/logstream

Answer 3

我不喜歡@neustart47 的回答，因為它不必要地復雜，但他說IApplicationLifetime已經過時是對的。

取自Microsoft Docs

//  1. Add the interface `IHostedService` to the class you would like
//     to be called during an application event. 
internal class LifetimeEventsHostedService : IHostedService
{
    private readonly ILogger _logger;
    private readonly IHostApplicationLifetime _appLifetime;

    // 2. Inject `IHostApplicationLifetime` through dependency injection in the constructor.
    public LifetimeEventsHostedService(
        ILogger<LifetimeEventsHostedService> logger, 
        IHostApplicationLifetime appLifetime)
    {
        _logger = logger;
        _appLifetime = appLifetime;
    }

    // 3. Implemented by `IHostedService`, setup here your event registration. 
    public Task StartAsync(CancellationToken cancellationToken)
    {
        _appLifetime.ApplicationStarted.Register(OnStarted);
        _appLifetime.ApplicationStopping.Register(OnStopping);
        _appLifetime.ApplicationStopped.Register(OnStopped);

        return Task.CompletedTask;
    }

    // 4. Implemented by `IHostedService`, setup here your shutdown registration.
    //    If you have nothing to stop, then just return `Task.CompletedTask`
    public Task StopAsync(CancellationToken cancellationToken)
    {
        return Task.CompletedTask;
    }

    private void OnStarted()
    {
        _logger.LogInformation("OnStarted has been called.");

        // Perform post-startup activities here
    }

    private void OnStopping()
    {
        _logger.LogInformation("OnStopping has been called.");

        // Perform on-stopping activities here
    }

    private void OnStopped()
    {
        _logger.LogInformation("OnStopped has been called.");

        // Perform post-stopped activities here
    }
}

完畢！

Answer 4

使用頂部答案中建議的Microsoft.AspNetCore.Hosting.IApplicationLifetime現在已過時。

[Obsolete("This type is obsolete and will be removed in a future version. The recommended alternative is Microsoft.Extensions.Hosting.IHostApplicationLifetime.", false)]
public interface IApplicationLifetime

使用IHostApplicationLifetime在應用程序關閉時觸發回調。

在某處添加：

public static async Task WaitForShutdownAsync(this IHost host)
{
    // Get the lifetime object from the DI container
    var applicationLifetime = host.Services.GetService<IHostApplicationLifetime>();

    // Create a new TaskCompletionSource called waitForStop
    var waitForStop = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);

    // Register a callback with the ApplicationStopping cancellation token
    applicationLifetime.ApplicationStopping.Register(obj =>
    {
        var tcs = (TaskCompletionSource<object>)obj;

        //PUT YOUR CODE HERE 

        // When the application stopping event is fired, set 
        // the result for the waitForStop task, completing it
        tcs.TrySetResult(null);
    }, waitForStop);

    // Await the Task. This will block until ApplicationStopping is triggered,
    // and TrySetResult(null) is called
    await waitForStop.Task;

    // We're shutting down, so call StopAsync on IHost
    await host.StopAsync();
}

然后我在 Program.cs 中使用它：

var host = CreateHostBuilder(args).Build();
host.WaitForShutdownAsync();

其他回調也是如此。 您可以在此處找到更多信息

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