Durable subscrption state is part of the MQTT specification which has
not been supported until now. This functionality is implemented via an
internal last-value queue. When an MQTT client creates, updates, or
adds a subscription a message using the client-ID as the last-value is
sent to the internal queue. When the broker restarts this data is read
from the queue and populates the in-memory MQTT data-structures.
Therefore subscribers can reconnect and resume their session's
subscriptions without have to manually resubscribe.
MQTT state is now managed centrally per-broker rather than in the
MQTTProtocolManager since there is one instance of MQTTProtocolManager
for each acceptor allowing MQTT connections. Managing state per acceptor
would allow odd behavior with clients connecting to different acceptors
with the same client ID.
The subscriptions are serialized as raw bytes with a "version" byte for
potential future use, but I intentionally avoided adding complex
scaffolding to support multiple versions. We can add that complexity
later if necessary.
Some tests needed to be changed since instantiating an MQTT protocol
manager now creates an internal queue. A handful of tests assume that no
queues will exist other than the ones they create themselves. I updated
the main test super-class so that an MQTT protocol manager is not
automatically instantiated when configuring a broker for in-vm support.
When skipping the authentication cache details for the original
exception are not logged.
This commit ensures these details are logged and adopts the
ExceptionUtils class from Apache Commons Lang in lieu of the previous
custom implementation.
I am adding three attributes to Address-settings:
* page-limit-bytes: Number of bytes. We will convert this metric into max number of pages internally by dividing max-bytes / page-size. It will allow a max based on an estimate.
* page-limit-messages: Number of messages
* page-full-message-policy: fail or drop
We will now allow paging, until these max values and then fail or drop messages.
Once these values are retracted, the address will remain full until a period where cleanup is kicked in by paging. So these values may have a certain delay on being applied, but they should always be cleared once cleanup happened.
Clebert Suconic
Justin Bertram
Domenico Francesco Bruscino
Alexey Markevich
Robbie Gemmell