.NET Core 2.1引入了新的通用主机（Generic Host），可以利用Web Host的所有优势来托管非HTTP工作负载。目前关于它的信息和使用方法不是很多，但我将以下文章作为起点:
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/host/generic-host?view=aspnetcore-2.1
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/host/hosted-services?view=aspnetcore-2.1
我的.NET Core应用程序启动后，通过RabbitMQ消息代理监听新请求，并在用户请求下关闭（通常通过控制台中的Ctrl+C）。然而, 关闭并不完美 - 应用程序返回控制权给操作系统时仍存在未完成的后台线程。我可以通过控制台消息看到它的存在 - 当我在控制台中按下Ctrl+C时，我会看到我的应用程序输出几行控制台消息，然后是操作系统命令提示符，再然后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;
}
}
}
}
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;
}
}
当我按下Ctrl+C时，在控制台中看到以下输出（当没有请求正在处理时）：
停止工作池...
命令提示符
工人id：处理完毕。
如何优雅地关闭？