【发布时间】：2018-12-05 06:53:11
【问题描述】：
.NET Core 2.1 引入了新的通用主机，它允许托管具有 Web 主机所有优势的非 HTTP 工作负载。目前，没有太多的信息和食谱，但我以以下文章为起点：
https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/generic-host?view=aspnetcore-2.1
https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/hosted-services?view=aspnetcore-2.1
我的 .NET Core 应用程序启动，通过 RabbitMQ 消息代理侦听新请求并根据用户请求关闭（通常通过控制台中的 Ctrl+C）。然而，关机不是优雅的——应用程序在将控制权返回给操作系统时仍有未完成的后台线程。我通过控制台消息看到它 - 当我在控制台中按 Ctrl+C 时，我看到我的应用程序有几行控制台输出，然后是操作系统命令提示符，然后又是我的应用程序的控制台输出。
这是我的代码：
Program.cs
public class Program
{
public static async Task Main(string[] args)
{
var host = new HostBuilder()
.ConfigureHostConfiguration(config =>
{
config.SetBasePath(AppContext.BaseDirectory);
config.AddEnvironmentVariables(prefix: "ASPNETCORE_");
config.AddJsonFile("hostsettings.json", optional: true);
})
.ConfigureAppConfiguration((context, config) =>
{
var env = context.HostingEnvironment;
config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
config.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
if (env.IsProduction())
config.AddDockerSecrets();
config.AddEnvironmentVariables();
})
.ConfigureServices((context, services) =>
{
services.AddLogging();
services.AddHostedService<WorkerPoolHostedService>();
// ... other services
})
.ConfigureLogging((context, logging) =>
{
if (context.HostingEnvironment.IsDevelopment())
logging.AddDebug();
logging.AddSerilog(dispose: true);
Log.Logger = new LoggerConfiguration()
.ReadFrom.Configuration(context.Configuration)
.CreateLogger();
})
.UseConsoleLifetime()
.Build();
await host.RunAsync();
}
}
WorkerPoolHostedService.cs
internal class WorkerPoolHostedService : IHostedService
{
private IList<VideoProcessingWorker> _workers;
private CancellationTokenSource _stoppingCts = new CancellationTokenSource();
protected WorkerPoolConfiguration WorkerPoolConfiguration { get; }
protected RabbitMqConfiguration RabbitMqConfiguration { get; }
protected IServiceProvider ServiceProvider { get; }
protected ILogger<WorkerPoolHostedService> Logger { get; }
public WorkerPoolHostedService(
IConfiguration configuration,
IServiceProvider serviceProvider,
ILogger<WorkerPoolHostedService> logger)
{
this.WorkerPoolConfiguration = new WorkerPoolConfiguration(configuration);
this.RabbitMqConfiguration = new RabbitMqConfiguration(configuration);
this.ServiceProvider = serviceProvider;
this.Logger = logger;
}
public async Task StartAsync(CancellationToken cancellationToken)
{
var connectionFactory = new ConnectionFactory
{
AutomaticRecoveryEnabled = true,
UserName = this.RabbitMqConfiguration.Username,
Password = this.RabbitMqConfiguration.Password,
HostName = this.RabbitMqConfiguration.Hostname,
Port = this.RabbitMqConfiguration.Port,
VirtualHost = this.RabbitMqConfiguration.VirtualHost
};
_workers = Enumerable.Range(0, this.WorkerPoolConfiguration.WorkerCount)
.Select(i => new VideoProcessingWorker(
connectionFactory: connectionFactory,
serviceScopeFactory: this.ServiceProvider.GetRequiredService<IServiceScopeFactory>(),
logger: this.ServiceProvider.GetRequiredService<ILogger<VideoProcessingWorker>>(),
cancellationToken: _stoppingCts.Token))
.ToList();
this.Logger.LogInformation("Worker pool started with {0} workers.", this.WorkerPoolConfiguration.WorkerCount);
}
public async Task StopAsync(CancellationToken cancellationToken)
{
this.Logger.LogInformation("Stopping working pool...");
try
{
_stoppingCts.Cancel();
await Task.WhenAll(_workers.SelectMany(w => w.ActiveTasks).ToArray());
}
catch (AggregateException ae)
{
ae.Handle((Exception exc) =>
{
this.Logger.LogError(exc, "Error while cancelling workers");
return true;
});
}
finally
{
if (_workers != null)
{
foreach (var worker in _workers)
worker.Dispose();
_workers = null;
}
}
}
}
VideoProcessingWorker.cs
internal class VideoProcessingWorker : IDisposable
{
private readonly Guid _id = Guid.NewGuid();
private bool _disposed = false;
protected IConnection Connection { get; }
protected IModel Channel { get; }
protected IServiceScopeFactory ServiceScopeFactory { get; }
protected ILogger<VideoProcessingWorker> Logger { get; }
protected CancellationToken CancellationToken { get; }
public VideoProcessingWorker(
IConnectionFactory connectionFactory,
IServiceScopeFactory serviceScopeFactory,
ILogger<VideoProcessingWorker> logger,
CancellationToken cancellationToken)
{
this.Connection = connectionFactory.CreateConnection();
this.Channel = this.Connection.CreateModel();
this.Channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: false);
this.ServiceScopeFactory = serviceScopeFactory;
this.Logger = logger;
this.CancellationToken = cancellationToken;
#region [ Declare ]
// ...
#endregion
#region [ Consume ]
// ...
#endregion
}
// ... worker logic ...
public void Dispose()
{
if (!_disposed)
{
this.Channel.Close(200, "Goodbye");
this.Channel.Dispose();
this.Connection.Close();
this.Connection.Dispose();
this.Logger.LogDebug("Worker {0}: disposed.", _id);
}
_disposed = true;
}
}
所以，当我按下 Ctrl+C 时，我会在控制台中看到以下输出（当没有请求处理时）：
正在停止工作池...
命令提示符
工人 id：已处置。
如何优雅关机？
【问题讨论】：
-
工人听取消令牌吗？
// ... worker logic ..中的代码应该定期检查this.CancellationToken并在收到信号时退出 -
@PanagiotisKanavos 是的，当然
-
目前还不清楚您在 VideoProcessingWorker 中究竟对令牌做了什么。您是在检查 IsCancellationRequested 还是正在传递令牌，以便一些任务可以通过抛出 TaskCancelledException 来取消。 StopAsyc 方法可以持续到无限期等待完成，因此您显示的代码看起来是正确的，问题似乎隐藏在未显示的部分中。如果您可以使用可以发布的更简单的代码重现该问题，那就太好了。
标签： c# .net asp.net-core .net-core