Fix service hangs when stopping

src/NATS.Client.Services/NatsSvcServer.cs

@@ -60,7 +60,18 @@ public async ValueTask StopAsync(CancellationToken cancellationToken = default)
         }
 
         // Drain buffers
-        await _nats.PingAsync(cancellationToken);
+        // Ping only when connection is open, otherwise ping hangs waiting for reconnection.
+        // This is problematic when stopping a service during connection issues
+        // or if the server is stopped especially in a test environment.
+        if (_nats.ConnectionState == NatsConnectionState.Open)
+        {
+            // We're stopping, so timeout quickly in case connection state changes
+            // which means we don't care about flushing any buffers anymore
+            // it's just a best effort attempt
+            using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(_cts.Token, cancellationToken);
+            linkedCts.CancelAfter(_nats.Opts.ConnectTimeout);
+            await _nats.PingAsync(linkedCts.Token).ConfigureAwait(false);
+        }
 
         foreach (var ep in _endPoints.Values)
         {

tests/NATS.Client.Services.Tests/ServicesTests.cs

@@ -4,6 +4,7 @@
 using NATS.Client.Platform.Windows.Tests;
 using NATS.Client.Services.Internal;
 using NATS.Client.Services.Models;
+using NATS.Client.TestUtilities2;
 
 namespace NATS.Client.Services.Tests;
 
@@ -481,6 +482,46 @@ await s2.AddEndpointAsync<string>(
         }
     }
 
+    [Fact]
+    public async Task Service_dispose_should_not_hang_when_connection_is_not_open()
+    {
+        await using var server = await NatsServerProcess.StartAsync();
+        await using var nats = new NatsConnection(new NatsOpts { Url = server.Url });
+        await nats.ConnectRetryAsync();
+        var svc = new NatsSvcContext(nats);
+
+        var cts = new CancellationTokenSource(TimeSpan.FromSeconds(120));
+        var cancellationToken = cts.Token;
+
+        // Service stoppes and disposed normally when connection is open
+        var s1 = await svc.AddServiceAsync($"s1", "1.0.0", cancellationToken: cancellationToken);
+        await s1.StopAsync(cancellationToken);
+        await s1.DisposeAsync();
+
+        // Service stop/dispose should not hang when connection is closed
+        var s2 = await svc.AddServiceAsync($"s2", "1.0.0", cancellationToken: cancellationToken);
+
+        // Stop the server to close the connection
+        await server.StopAsync();
+
+        // Check that StopAsync does not hang
+        var task = s2.StopAsync(cancellationToken).AsTask();
+        var timeoutTask = Task.Delay(TimeSpan.FromSeconds(60), cancellationToken);
+        await Task.WhenAny(task, timeoutTask).ContinueWith(
+            completedTask =>
+            {
+                if (completedTask.Result == timeoutTask)
+                {
+                    throw new Exception("Service hanged!");
+                }
+
+                return task;
+            },
+            cancellationToken).Unwrap();
+
+        await s2.DisposeAsync();
+    }
+
     [Theory]
     [InlineData("foo bar")]
     [InlineData("foo\tbar")]