feat: add ServerStats counters and NatsClient metadata for monitoring

tests/NATS.Server.Tests/ClientTests.cs

@@ -39,7 +39,7 @@ public class ClientTests : IAsyncDisposable
             Port = 4222,
         };
 
-        _natsClient = new NatsClient(1, _serverSocket, new NatsOptions(), serverInfo, NullLogger.Instance);
+        _natsClient = new NatsClient(1, _serverSocket, new NatsOptions(), serverInfo, NullLogger.Instance, new ServerStats());
     }
 
     public async ValueTask DisposeAsync()

tests/NATS.Server.Tests/ServerStatsTests.cs

@@ -0,0 +1,84 @@
+using System.Net;
+using System.Net.Sockets;
+using Microsoft.Extensions.Logging.Abstractions;
+using NATS.Server;
+
+namespace NATS.Server.Tests;
+
+public class ServerStatsTests : IAsyncLifetime
+{
+    private readonly NatsServer _server;
+    private readonly int _port;
+    private readonly CancellationTokenSource _cts = new();
+
+    public ServerStatsTests()
+    {
+        _port = GetFreePort();
+        _server = new NatsServer(new NatsOptions { Port = _port }, NullLoggerFactory.Instance);
+    }
+
+    public async Task InitializeAsync()
+    {
+        _ = _server.StartAsync(_cts.Token);
+        await _server.WaitForReadyAsync();
+    }
+
+    public Task DisposeAsync()
+    {
+        _cts.Cancel();
+        _server.Dispose();
+        return Task.CompletedTask;
+    }
+
+    [Fact]
+    public void Server_has_start_time()
+    {
+        _server.StartTime.ShouldNotBe(default);
+        _server.StartTime.ShouldBeLessThanOrEqualTo(DateTime.UtcNow);
+    }
+
+    [Fact]
+    public async Task Server_tracks_total_connections()
+    {
+        using var sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+        await sock.ConnectAsync(new IPEndPoint(IPAddress.Loopback, _port));
+        await Task.Delay(100);
+        _server.Stats.TotalConnections.ShouldBeGreaterThanOrEqualTo(1);
+    }
+
+    [Fact]
+    public async Task Server_stats_track_messages()
+    {
+        using var pub = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+        await pub.ConnectAsync(new IPEndPoint(IPAddress.Loopback, _port));
+
+        var buf = new byte[4096];
+        await pub.ReceiveAsync(buf, SocketFlags.None); // INFO
+
+        await pub.SendAsync("CONNECT {}\r\nSUB test 1\r\nPUB test 5\r\nhello\r\n"u8.ToArray());
+        await Task.Delay(200);
+
+        _server.Stats.InMsgs.ShouldBeGreaterThanOrEqualTo(1);
+        _server.Stats.InBytes.ShouldBeGreaterThanOrEqualTo(5);
+    }
+
+    [Fact]
+    public async Task Client_has_metadata()
+    {
+        using var sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+        await sock.ConnectAsync(new IPEndPoint(IPAddress.Loopback, _port));
+        await Task.Delay(100);
+
+        var client = _server.GetClients().First();
+        client.RemoteIp.ShouldNotBeNullOrEmpty();
+        client.RemotePort.ShouldBeGreaterThan(0);
+        client.StartTime.ShouldNotBe(default);
+    }
+
+    private static int GetFreePort()
+    {
+        using var sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+        sock.Bind(new IPEndPoint(IPAddress.Loopback, 0));
+        return ((IPEndPoint)sock.LocalEndPoint!).Port;
+    }
+}