From 07bd63f8085de6a471000854c4dbeca9bf402468 Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Thu, 18 Jun 2026 11:50:07 -0400
Subject: [PATCH] fix(adminui): /hosts timer dispose-race hardening +
 IAsyncDisposable parity with DriverStatusPanel (review)

---
 .../Components/Pages/Hosts.razor              | 27 +++++++++++++------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Hosts.razor b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Hosts.razor
index d0cec0e0..069df324 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Hosts.razor
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Hosts.razor
@@ -18,7 +18,7 @@
 @inject IDriverStatusSnapshotStore DriverStore
 @inject IDbContextFactory<OtOpcUaConfigDbContext> DbFactory
 @inject Microsoft.Extensions.Logging.ILogger<Hosts> Logger
-@implements IDisposable
+@implements IAsyncDisposable
 
 <div class="d-flex justify-content-between align-items-center mb-3">
     <h4 class="mb-0">Cluster hosts</h4>
@@ -226,12 +226,20 @@ else
         await LoadConfigAsync();
         RebuildDriverGroups();
         DriverStore.SnapshotChanged += OnSnapshotChanged;
-        _timer = new Timer(_ => InvokeAsync(async () =>
+        _timer = new Timer(_ => _ = InvokeAsync(async () =>
             {
-                Refresh();
-                await LoadConfigAsync();
-                RebuildDriverGroups();
-                StateHasChanged();
+                try
+                {
+                    Refresh();
+                    await LoadConfigAsync();
+                    RebuildDriverGroups();
+                    StateHasChanged();
+                }
+                catch (Exception ex) when (ex is ObjectDisposedException or OperationCanceledException)
+                {
+                    // Circuit disposed while a tick was in flight — ignore (the discarded task would
+                    // otherwise swallow this silently). Mirrors DriverStatusPanel's drain-on-dispose.
+                }
             }), null,
             TimeSpan.FromSeconds(RefreshIntervalSeconds),
             TimeSpan.FromSeconds(RefreshIntervalSeconds));
@@ -337,10 +345,13 @@ else
         _              => "chip-idle",
     };
 
-    public void Dispose()
+    public async ValueTask DisposeAsync()
     {
-        _timer?.Dispose();
+        // Unsubscribe first so the singleton store can't invoke a handler on a disposed component.
         DriverStore.SnapshotChanged -= OnSnapshotChanged;
+        // Drain the timer so an in-flight callback can't touch a component that's already gone
+        // (System.Threading.Timer's async dispose awaits any in-flight callback — .NET 6+).
+        if (_timer is not null) await _timer.DisposeAsync();
     }
 
     private sealed record MemberRow(