Support delaying PUBACKs in libmosquitto API

[ralight]

migrated from Bugzilla #452930
status NEW severity enhancement in component Mosquitto client library for ---
Reported in version unspecified on platform PC
Assigned to: Roger Light

On 2014-11-23 17:37:39 -0500, Roger Light wrote:

(imported from launchpad)

In the situation where a libmosquitto-based client subscribes to a topic with QoS=1, it would be useful to be able to delay the PUBACKs that it sends back.
Instead of the current automatic behavior, the API would provide a callback to manually send a PUBACK for a specific message.
The idea being that it confirms that the message has been correctly processed locally and is ready to be acknowledged to the broker.

The feature was already mentioned in a message from the mailing-list a year ago: https://lists.launchpad.net/mosquitto-users/msg00024.html

And I see that the MQTT.js implementation supports such a feature: mqttjs/MQTT.js#77