ServerService.cs

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using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.EventLog;
using Microsoft.Extensions.Logging.EventLog.Internal;
using System;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.ServiceProcess;
using System.Threading;
using System.Threading.Tasks;
using Tgstation.Server.Host.Watchdog;

namespace Tgstation.Server.Host.Service
{
    sealed class ServerService : ServiceBase, IEventLog
    {
        public const string Name = "tgstation-server-4";

        readonly IWatchdog watchdog;

        Task watchdogTask;

        CancellationTokenSource cancellationTokenSource;

        public ServerService(IWatchdogFactory watchdogFactory, ILoggerFactory loggerFactory, LogLevel minumumLogLevel)
        {
            if (watchdogFactory == null)
                throw new ArgumentNullException(nameof(watchdogFactory));
            if (loggerFactory == null)
                throw new ArgumentNullException(nameof(loggerFactory));

            loggerFactory.AddEventLog(new EventLogSettings
            {
                EventLog = this,
                Filter = (message, logLevel) => logLevel >= minumumLogLevel
            });

            ServiceName = Name;
            watchdog = watchdogFactory.CreateWatchdog(loggerFactory);
        }

        public int MaxMessageSize => (int)EventLog.MaximumKilobytes * 1024;

        public void WriteEntry(string message, EventLogEntryType type, int eventID, short category) => EventLog.WriteEntry(message, type, eventID, category);

        async Task RunWatchdog(string[] args, CancellationToken cancellationToken)
        {
            await watchdog.RunAsync(false, args, cancellationToken).ConfigureAwait(false);

            void StopServiceAsync()
            {
                try
                {
                    Task.Run(Stop, cancellationToken);
                }
                catch (OperationCanceledException) { }
                catch (Exception e)
                {
                    EventLog.WriteEntry(String.Format(CultureInfo.InvariantCulture, "Error stopping service! Exception: {0}", e));
                }
            }
            StopServiceAsync();
        }

        [SuppressMessage("Microsoft.Usage", "CA2213:DisposableFieldsShouldBeDisposed", MessageId = "cancellationTokenSource")]
        protected override void Dispose(bool disposing)
        {
            cancellationTokenSource?.Dispose();
            base.Dispose(disposing);
        }

        protected override void OnStart(string[] args)
        {
            cancellationTokenSource?.Dispose();
            cancellationTokenSource = new CancellationTokenSource();
            watchdogTask = RunWatchdog(args, cancellationTokenSource.Token);
        }

        protected override void OnStop()
        {
            cancellationTokenSource.Cancel();
            watchdogTask.GetAwaiter().GetResult();
        }
    }
}