fix: address MonitorServer review — dispose resources, add cancellation, improve test reliability

src/NATS.Server/Monitoring/MonitorServer.cs

@@ -13,6 +13,7 @@ public sealed class MonitorServer : IAsyncDisposable
 {
     private readonly WebApplication _app;
     private readonly ILogger<MonitorServer> _logger;
+    private readonly VarzHandler _varzHandler;
 
     public MonitorServer(NatsServer server, NatsOptions options, ServerStats stats, ILoggerFactory loggerFactory)
     {
@@ -25,7 +26,7 @@ public sealed class MonitorServer : IAsyncDisposable
         _app = builder.Build();
         var basePath = options.MonitorBasePath ?? "";
 
-        var varzHandler = new VarzHandler(server, options);
+        _varzHandler = new VarzHandler(server, options);
 
         _app.MapGet(basePath + "/", () =>
         {
@@ -44,10 +45,10 @@ public sealed class MonitorServer : IAsyncDisposable
             stats.HttpReqStats.AddOrUpdate("/healthz", 1, (_, v) => v + 1);
             return Results.Ok("ok");
         });
-        _app.MapGet(basePath + "/varz", async () =>
+        _app.MapGet(basePath + "/varz", async (HttpContext ctx) =>
         {
             stats.HttpReqStats.AddOrUpdate("/varz", 1, (_, v) => v + 1);
-            return Results.Ok(await varzHandler.HandleVarzAsync());
+            return Results.Ok(await _varzHandler.HandleVarzAsync(ctx.RequestAborted));
         });
 
         // Stubs for unimplemented endpoints
@@ -106,6 +107,8 @@ public sealed class MonitorServer : IAsyncDisposable
 
     public async ValueTask DisposeAsync()
     {
+        await _app.StopAsync();
         await _app.DisposeAsync();
+        _varzHandler.Dispose();
     }
 }

src/NATS.Server/Monitoring/VarzHandler.cs

@@ -8,7 +8,7 @@ namespace NATS.Server.Monitoring;
 /// Handles building the Varz response from server state and process metrics.
 /// Corresponds to Go server/monitor.go handleVarz function.
 /// </summary>
-public sealed class VarzHandler
+public sealed class VarzHandler : IDisposable
 {
     private readonly NatsServer _server;
     private readonly NatsOptions _options;
@@ -21,17 +21,17 @@ public sealed class VarzHandler
     {
         _server = server;
         _options = options;
-        var proc = Process.GetCurrentProcess();
+        using var proc = Process.GetCurrentProcess();
         _lastCpuSampleTime = DateTime.UtcNow;
         _lastCpuUsage = proc.TotalProcessorTime;
     }
 
-    public async Task<Varz> HandleVarzAsync()
+    public async Task<Varz> HandleVarzAsync(CancellationToken ct = default)
     {
-        await _varzMu.WaitAsync();
+        await _varzMu.WaitAsync(ct);
         try
         {
-            var proc = Process.GetCurrentProcess();
+            using var proc = Process.GetCurrentProcess();
             var now = DateTime.UtcNow;
             var uptime = now - _server.StartTime;
             var stats = _server.Stats;
@@ -100,6 +100,11 @@ public sealed class VarzHandler
         }
     }
 
+    public void Dispose()
+    {
+        _varzMu.Dispose();
+    }
+
     /// <summary>
     /// Formats a TimeSpan as a human-readable uptime string matching Go server format.
     /// </summary>

tests/NATS.Server.Tests/MonitorTests.cs

@@ -27,8 +27,17 @@ public class MonitorTests : IAsyncLifetime
     {
         _ = _server.StartAsync(_cts.Token);
         await _server.WaitForReadyAsync();
-        // Give monitoring server time to start
-        await Task.Delay(200);
+        // Wait for monitoring HTTP server to be ready
+        for (int i = 0; i < 50; i++)
+        {
+            try
+            {
+                var response = await _http.GetAsync($"http://127.0.0.1:{_monitorPort}/healthz");
+                if (response.IsSuccessStatusCode) break;
+            }
+            catch (HttpRequestException) { }
+            await Task.Delay(50);
+        }
     }
 
     public async Task DisposeAsync()