If there are no longer any publishers or subscribers reading nor writing to a Queue, Topic, or Subscription, because of crashes or other abnormal terminations (instance restart, etc.), is that Queue/Topic/Subscription effectively orphaned?
I tested this by creating a few Queues, and then terminating the applications. Those Queues were still on the Service Bus a long time later. It seems that they will just stay there forever. That would be wonderful if we WANTED that behavior, but in this case, we do not.
How can we detect and delete these Queues, Topics, and Subscriptions? They will count towards Azure limits, etc, and we cannot have these orphaned processes every time an instance is restarted/patched/crashes.
If it helps make the question clearer, this is a unique situation in which the Queues/Topics/Subscriptions have special names, or special Filters, and a very limited set of publishers (1) and subscribers (1) for a limited time. This is not a case where we want survivability. These are instance-specific response channels. Whether we use Queues or Subscriptions is immaterial. If the instance is gone, so is the need for that Queue (or Subscription).
This is part of a solution where each web role has a dedicated response channel that it monitors. At any time, this web role may have dozens of requests pending via other messaging channels (Queues/Topics), and it is waiting for the answers on multiple threads. We need the response to come back to the thread that placed the message, so that the web role can respond to the caller. It is no good in this situation to simply have a Subscription based on the machine, because it will be receiving messages for other threads. We need each publishing thread to establish a dedicated response channel, so that the only thing on that channel is the response for that thread.
Even if we use Subscriptions (with some kind of instance-related filter) to do a long-polling receive operation on the Subscription, if the web role instance dies, that Subscription will be orphaned, correct?
This question can be boiled down like so: If there are no more publishers or subscribers to a Queue/Topic/Subscription, then that service is effectively orphaned. How can those orphans be detected and cleaned up?
In this scenario you are looking for the Queue/Subscriptions to be "dynamic" in nature. They would be created and removed based on use as opposed to the current explicit provisioning model for these entities. Service Bus provides you with the APIs to perform create/delete operations so you can plug these on role OnStart/OnStop events appropriately. If those operations fail for some reason then the orphaned entities will exist. Again you can run clean up operation on them based on some unique identifier for the name of the entities. An example of this can be seen here: http://windowsazurecat.com/2011/08/how-to-simplify-scale-inter-role-communication-using-windows-azure-service-bus/
In the near future we will add more metadata and query capabilities to Queues/Topics/Subscriptions so you can see when they were last accessed and make cleanup decisions.