fix(session): bound a routed request and stop hiding a failed subscribe

Emby.Server.Implementations/Session/RedisPodMessageBus.cs

@@ -52,14 +52,9 @@ public sealed class RedisPodMessageBus : IPodMessageBus
         _timeout = TimeSpan.FromSeconds(Math.Max(1, options.Value.OperationTimeoutSeconds));
         PodId = podId;
 
-        try
-        {
-            _subscriber.Subscribe(RedisChannel.Literal(ChannelPrefix + PodId), (_, value) => Dispatch(value));
-        }
-        catch (Exception ex)
-        {
-            _logger.LogWarning(ex, "Failed to subscribe to {PodId}; messages routed here are dropped.", PodId);
-        }
+        // A bus that cannot subscribe can only send, so every request it makes waits out the timeout and
+        // nothing routed here is ever answered. The caller degrades the pair to single-instance instead.
+        _subscriber.Subscribe(RedisChannel.Literal(ChannelPrefix + PodId), (_, value) => Dispatch(value));
     }
 
     /// <inheritdoc />
@@ -77,20 +72,25 @@ public sealed class RedisPodMessageBus : IPodMessageBus
         var acknowledged = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
         _pending[message.CorrelationId] = acknowledged;
 
+        // Publish and acknowledgement share one deadline, so a request is bounded by the timeout rather
+        // than by twice it.
+        using var deadline = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        deadline.CancelAfter(_timeout);
+
         try
         {
             var subscribers = await _subscriber.PublishAsync(
                 RedisChannel.Literal(ChannelPrefix + targetPod),
-                JsonSerializer.Serialize(message, _jsonOptions)).WaitAsync(_timeout, cancellationToken).ConfigureAwait(false);
+                JsonSerializer.Serialize(message, _jsonOptions)).WaitAsync(deadline.Token).ConfigureAwait(false);
 
             if (subscribers == 0)
             {
                 return false;
             }
 
-            return await acknowledged.Task.WaitAsync(_timeout, cancellationToken).ConfigureAwait(false);
+            return await acknowledged.Task.WaitAsync(deadline.Token).ConfigureAwait(false);
         }
-        catch (TimeoutException)
+        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
         {
             _logger.LogWarning("Instance {TargetPod} did not acknowledge a {Kind} message within {Timeout}.", targetPod, message.Kind, _timeout);
             return false;