.net-core - .NET 核心 BackgroundService 没有作为守护进程正常关闭

Question

我正在开发 .NET Core 3.1 后台服务，该服务将作为守护进程安装在 Debian AWS EC2 实例上。
优雅地关闭守护进程以停止运行任务并完成一些要处理的任务(发送一些事件等)是很重要的。基本实现如下所示:

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace MyApp.WorkerService
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).UseSystemd().Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureServices((hostContext, services) =>
                {
                    services.AddHostedService<Worker>();
                });        
    }
}

你可以看到我在这里使用了 SystemdLifetime。

worker 如下:

using System;
using System.Threading;
using System.Threading.Tasks;
using AdClassifier.App.Audit;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using NLog;

namespace MyApp.WorkerService
{
    public class Worker : BackgroundService
    {
        private static readonly ILogger Logger = LogManager.GetLogger(typeof(Worker).FullName);

        private readonly int _jobPollIntervalMilliseconds;

        public IServiceProvider Services { get; }

        public Worker(IServiceProvider services, IConfiguration configuration)
        {
            Services = services;
            _jobPollIntervalMilliseconds = configuration.GetValue<int>("JobPollIntervalMilliseconds");
        }

        protected override Task ExecuteAsync(CancellationToken stoppingToken)
        {
            Logger.Info("Worker running.");
            var task = new Task(o => DoWork(stoppingToken), stoppingToken);
            task.Start();
            return task;
        }

        public override async Task StopAsync(CancellationToken cancellationToken)
        {
            Logger.Info("Worker stopping");
            await base.StopAsync(cancellationToken);
            Logger.Info("Worker stopped");
        }

        private void DoWork(CancellationToken stoppingToken)
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                using (var scope = Services.CreateScope())
                {
                    // do some work
                }

                Thread.Sleep(_jobPollIntervalMilliseconds);
            }
            Logger.Info("cancellation requested!");
        }        
    }
}

问题
正如我提到的，我们将其设置为守护进程，如下所示

[Unit]
Description=my worker
Requires=deploy-my-worker.service
After=multi-user.target deploy-my-worker.service
ConditionFileIsExecutable=/home/my-worker/current/myworker
[Service]
Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false
Environment=DOTNET_CLI_TELEMETRY_OPTOUT=true
Environment=ASPNETCORE_URLS=http://*:5000
Environment=DOTNET_ENVIRONMENT=Staging
Environment=ASPNETCORE_ENVIRONMENT=Staging
WorkingDirectory=/home/my-worker/current
ExecStart=/home/my-worker/current/myworker
SyslogIdentifier=my-worker
Restart=always
RestartSec=10
KillSignal=SIGTERM
User=usr
Group=usrgroup
[Install]
WantedBy=multi-user.target

问题是 worker 不会优雅地停止。我正在检查以下日志条目的日志，但它们没有出现:
Worker 停止，取消请求!，Worker 停止
请注意，该应用程序确实关闭了。我们为关闭服务所做的尝试如下:

• 关闭服务器
• systemctl 停止 my-worker.service
• 杀死
• kill -SIGTERM
• kill -SIGINT

什么有效

如果我这样启动 worker:usr@ip-10-168-19-126:~/my-worker/current$ ./myworker 然后按 Ctrl-C (应该是 SIGINT)，应用程序停止，在我的日志中我可以看到正确的消息:

2020-05-21 16:16:57.9676|INFO|MyApp.WorkerService.Worker|Worker stopping 
2020-05-21 16:16:57.9937|INFO|MyApp.WorkerService.Worker|cancellation requested! 
2020-05-21 16:16:57.9937|INFO|MyApp.WorkerService.Worker|Worker stopped 
2020-05-21 16:16:57.9980 Info AppDomain Shutting down. Logger closing...

关于如何让守护进程按预期工作的任何想法？

注意:
我有充分的理由相信问题出在守护程序设置或 UseSystemd() 的某个地方。
我将 UseSystemd() 替换为 UseWindowsService() 并将其作为 Windows 服务安装在 Windows 机器上。然后继续通过“服务”面板启动和停止服务，并按预期看到关闭日志记录。
因此，我很想假设在实现中没有问题，而是在设置中的某个地方。

Answer 1

看来问题出在 NLog 的关闭上。这是通过执行以下操作修复的:LogManager.AutoShutdown = false; 并在 Worker::StopAsync 中添加 LogManager.Shutdown();