Major Description
In the PersistenceAdapter for the broker, you'll see the call getDestinations() which is used (At least in MQTT) on each connect to see if the connecting client has any subscriptions. The issue is that getDesitinations() returns all durable subscriptions. We have an environment which has status / state which are retained, as well, each client supports 10 durable subscriptions. With 10 K client connections this implies a dip into the DB which will return 80 bytes for each DESTINATION in the data base * 10K or 8 Meg on each connect. This needs to be filtered in the DB query since you are not looking for other clientids. All PersistenceAdaptors implemented have this issue.
I have modified the all the DB adaptors to support a new method called getDestinations(String client_id). I have also modified the JDBC query to support a query which is specific to a given client-id and does not need to loop through all (thousands of ) connections filtering the client_id in the code..
(see PersistenceAdapterSupport.listSubscriptions())..
I've also attached a JUnit test which demos the issue using derbyDb..
