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Question

I'm working with Azure ServiceBus, standard tier.

I'm trying to figure out what's happened since a couple of weeks, (it seems it started when bus traffic has increased, maybe 10-15 messages per second).

I have automatic creation of subscription using

subscriptionOpts.AutoDeleteOnIdle = TimeSpan.FromHours(3);

Starting from lasts weeks, (when we got a traffic increment), sometimes our subscriptionclients stopped receiving messages and after 3 hours they get deleted.

var messageOptions = new MessageHandlerOptions(args =>
    {
         Emaillog.Warn(args.Exception, $"Client ExceptionReceived: {args.Exception}");
         return Task.CompletedTask;
    }) { AutoComplete = true };
_subscriptionClient.RegisterMessageHandler(async (message, token) => await OnMessageReceived(message, $"{_subscriptionClient.SubscriptionName}", token), messageOptions);

Is it possible that a subscription client gets disconnected and doesn't connect anymore? I have 4-5 clients processes that connect to this topic, each one with his own subscription. When I find one of these subscriptions deleted, sometimes they have all been deleted, sometimes only some of them have been deleted.

Is it a bug? The only method call I do on the subscriptionClient is RegisterMessageHandler. I don't manage manually anything else...

Thank you in advance

Answer 1

The property AutoDeleteOnIdle is used to delete the Subscription when there is no message processing with in the Subscription for the specified time span.

As you mentioned that the message flow increased to 15 messages per second, there is no chance that the Subscription is left empty (with out message flow). So there is no reason for the Subscriptions to delete. The idleness of the Subscription is decided by both incoming and outgoing messages.

There can be chances that due to heavy message traffic, the downstream application processing the messages may went offline, leaving the messages unprocessed, eventually when the message flow reduced there is no receiver to process the messages, leaving the Subscription idle for 3 hours and delete.