stop heartbeat timers on subscription removal

Author: hansgschossmann

opcpublisher/OpcMonitoredItem.cs

@@ -456,7 +456,7 @@ public void MonitoredItemNotificationEventHandler(MonitoredItem monitoredItem, M
                 else
                 {
                     Logger.Debug($"Enqueue a new message from subscription {(monitoredItem.Subscription == null ? "removed" : monitoredItem.Subscription.Id.ToString(CultureInfo.InvariantCulture))}");
-                    Logger.Debug($" with publishing interval: {monitoredItem.Subscription.PublishingInterval} and sampling interval: {monitoredItem.SamplingInterval}):");
+                    Logger.Debug($" with publishing interval: {monitoredItem?.Subscription?.PublishingInterval} and sampling interval: {monitoredItem?.SamplingInterval}):");
                 }
 
                 // setupo heartbeat processing

opcpublisher/OpcSession.cs

@@ -618,6 +618,11 @@ public async Task<bool> StopMonitoringNodesAsync(CancellationToken ct)
                         {
                             // nodes may be tagged for stop before they are monitored, just continue
                         }
+                        // stop heartbeat timer for all items to remove
+                        foreach (var itemToRemove in itemsToRemove)
+                        {
+                            itemToRemove?.HeartbeatSendTimer?.Change(Timeout.Infinite, Timeout.Infinite);
+                        }
                         // remove them in our data structure
                         opcSubscription.OpcMonitoredItems.RemoveAll(i => i.State == OpcMonitoredItemState.RemovalRequested);
                         Interlocked.Increment(ref NodeConfigVersion);