fix(communication): key gRPC client cache by (site, endpoint) so per-session failover cannot dispose shared channels

tests/ZB.MOM.WW.ScadaBridge.Communication.Tests/Grpc/SiteStreamGrpcClientFactoryTests.cs

@@ -81,19 +81,47 @@ public class SiteStreamGrpcClientFactoryTests
     }
 
     [Fact]
-    public void GetOrCreate_EndpointChanged_DisposesPriorClient()
+    public void GetOrCreate_DifferentEndpointSameSite_KeepsBothClientsAlive()
     {
-        // Communication-013 regression: a later edit to a site's gRPC address must
-        // invalidate (and dispose) the stale cached client, so the corrected
-        // endpoint takes effect without a central restart.
+        // Arch review 02 (High): the cache is keyed by (site, endpoint). Both node
+        // channels for a site coexist, so a per-session NodeA→NodeB failover flip
+        // must NOT dispose the other endpoint's channel — another debug session may
+        // be using it. (Supersedes Communication-013's dispose-on-endpoint-change.)
         using var factory = new TrackingEndpointFactory();
 
-        var first = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5100");
-        var second = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5200");
+        var a = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5100");
+        var b = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5200");
 
-        Assert.NotSame(first, second);
-        Assert.True(first.Disposed, "stale client for the old endpoint should be disposed");
-        Assert.False(second.Disposed, "fresh client for the new endpoint should still be live");
+        Assert.NotSame(a, b);
+        Assert.False(a.Disposed, "the other endpoint's channel must stay alive");
+        Assert.Same(a, factory.GetOrCreate("site-a", "http://localhost:5100")); // still cached
+    }
+
+    [Fact]
+    public void TryGet_ReturnsCachedClientOrNull_WithoutCreating()
+    {
+        using var factory = new TrackingEndpointFactory();
+
+        Assert.Null(factory.TryGet("site-a", "http://localhost:5100"));
+        var a = factory.GetOrCreate("site-a", "http://localhost:5100");
+        Assert.Same(a, factory.TryGet("site-a", "http://localhost:5100"));
+        Assert.Null(factory.TryGet("site-a", "http://localhost:5200")); // other endpoint not cached
+        Assert.Equal(1, factory.CreatedCount); // TryGet never creates
+    }
+
+    [Fact]
+    public async Task RemoveSiteAsync_DisposesAllEndpointsForTheSite_OnlyThatSite()
+    {
+        using var factory = new TrackingEndpointFactory();
+        var a = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5100");
+        var b = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5200");
+        var other = (TrackingEndpointClient)factory.GetOrCreate("site-b", "http://localhost:5100");
+
+        await factory.RemoveSiteAsync("site-a");
+
+        Assert.True(a.Disposed);
+        Assert.True(b.Disposed);
+        Assert.False(other.Disposed);
     }
 
     [Fact]
@@ -126,7 +154,11 @@ public class SiteStreamGrpcClientFactoryTests
     private sealed class TrackingEndpointFactory : SiteStreamGrpcClientFactory
     {
         public TrackingEndpointFactory() : base(NullLoggerFactory.Instance) { }
+        public int CreatedCount { get; private set; }
         protected override SiteStreamGrpcClient CreateClient(string grpcEndpoint)
-            => new TrackingEndpointClient(grpcEndpoint);
+        {
+            CreatedCount++;
+            return new TrackingEndpointClient(grpcEndpoint);
+        }
     }
 }