feat: add signal handling (SIGTERM, SIGUSR2, SIGHUP) and CLI stubs

src/NATS.Server.Host/Program.cs

@@ -32,6 +32,15 @@ for (int i = 0; i < args.Length; i++)
         case "--https_port" when i + 1 < args.Length:
             options.MonitorHttpsPort = int.Parse(args[++i]);
             break;
+        case "-c" when i + 1 < args.Length:
+            options.ConfigFile = args[++i];
+            break;
+        case "--pid" when i + 1 < args.Length:
+            options.PidFile = args[++i];
+            break;
+        case "--ports_file_dir" when i + 1 < args.Length:
+            options.PortsFileDir = args[++i];
+            break;
         case "--tls":
             break;
         case "--tlscert" when i + 1 < args.Length:
@@ -50,18 +59,24 @@ for (int i = 0; i < args.Length; i++)
 }
 
 using var loggerFactory = new Serilog.Extensions.Logging.SerilogLoggerFactory(Log.Logger);
-var server = new NatsServer(options, loggerFactory);
+using var server = new NatsServer(options, loggerFactory);
 
-var cts = new CancellationTokenSource();
+// Register signal handlers
+server.HandleSignals();
+
+// Ctrl+C triggers graceful shutdown
 Console.CancelKeyPress += (_, e) =>
 {
     e.Cancel = true;
-    cts.Cancel();
+    Log.Information("Trapped SIGINT signal");
+    _ = Task.Run(async () => await server.ShutdownAsync());
 };
 
 try
 {
-    await server.StartAsync(cts.Token);
+    _ = server.StartAsync(CancellationToken.None);
+    await server.WaitForReadyAsync();
+    server.WaitForShutdown();
 }
 catch (OperationCanceledException)
 {

src/NATS.Server/NatsServer.cs

@@ -2,6 +2,7 @@ using System.Collections.Concurrent;
 using System.Net;
 using System.Net.Security;
 using System.Net.Sockets;
+using System.Runtime.InteropServices;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
 using Microsoft.Extensions.Logging;
@@ -42,6 +43,8 @@ public sealed class NatsServer : IMessageRouter, ISubListAccess, IDisposable
 
     private int _lameDuck;
 
+    private readonly List<PosixSignalRegistration> _signalRegistrations = [];
+
     private string? _portsFilePath;
 
     private static readonly TimeSpan AcceptMinSleep = TimeSpan.FromMilliseconds(10);
@@ -187,6 +190,50 @@ public sealed class NatsServer : IMessageRouter, ISubListAccess, IDisposable
         await ShutdownAsync();
     }
 
+    /// <summary>
+    /// Registers Unix signal handlers.
+    /// SIGTERM → shutdown, SIGUSR2 → lame duck, SIGUSR1 → log reopen (stub), SIGHUP → reload (stub).
+    /// </summary>
+    public void HandleSignals()
+    {
+        _signalRegistrations.Add(PosixSignalRegistration.Create(PosixSignal.SIGTERM, ctx =>
+        {
+            ctx.Cancel = true;
+            _logger.LogInformation("Trapped SIGTERM signal");
+            _ = Task.Run(async () => await ShutdownAsync());
+        }));
+
+        _signalRegistrations.Add(PosixSignalRegistration.Create(PosixSignal.SIGQUIT, ctx =>
+        {
+            ctx.Cancel = true;
+            _logger.LogInformation("Trapped SIGQUIT signal");
+            _ = Task.Run(async () => await ShutdownAsync());
+        }));
+
+        _signalRegistrations.Add(PosixSignalRegistration.Create(PosixSignal.SIGHUP, ctx =>
+        {
+            ctx.Cancel = true;
+            _logger.LogWarning("Trapped SIGHUP signal — config reload not yet supported");
+        }));
+
+        // SIGUSR1 and SIGUSR2 only on non-Windows
+        if (!OperatingSystem.IsWindows())
+        {
+            _signalRegistrations.Add(PosixSignalRegistration.Create((PosixSignal)10, ctx =>
+            {
+                ctx.Cancel = true;
+                _logger.LogWarning("Trapped SIGUSR1 signal — log reopen not yet supported");
+            }));
+
+            _signalRegistrations.Add(PosixSignalRegistration.Create((PosixSignal)12, ctx =>
+            {
+                ctx.Cancel = true;
+                _logger.LogInformation("Trapped SIGUSR2 signal — entering lame duck mode");
+                _ = Task.Run(async () => await LameDuckShutdownAsync());
+            }));
+        }
+    }
+
     public NatsServer(NatsOptions options, ILoggerFactory loggerFactory)
     {
         _options = options;
@@ -561,6 +608,8 @@ public sealed class NatsServer : IMessageRouter, ISubListAccess, IDisposable
     {
         if (!IsShuttingDown)
             ShutdownAsync().GetAwaiter().GetResult();
+        foreach (var reg in _signalRegistrations)
+            reg.Dispose();
         _quitCts.Dispose();
         _tlsRateLimiter?.Dispose();
         _listener?.Dispose();