Hello,

the presentity records (PUBLISH data) stored by the presence module needed always an external storage backend (sql/no-sql database), for subscriptions (active watchers) it was possible to use memory caching only.

I recently added support for cache-only module for PUBLISH data as well, more details are presented in the news article:

* https://www.kamailio.org/w/2020/05/in-memory-presentity-records/

That could help simplifying network architecture on distributed platforms leveraging cloud infrastructure and using replications mechanisms (e.g., dmq, evapi+pua_json, nsq, ...) between the Kamailio nodes.

The impact on the code was quite significant, given that any PUBLISH triggers a series of internal tasks (apply xcap rules, update watchers, ...), therefore I am calling for community testing to be sure old operational modes were not affected as well as testing the new mode to discover eventual issues -- just open an item on bug tracker when a problem is discovered.

Special credits to Fred Posner (lod.com) for supporting the development of this feature and to Emmanuel Schmidbauer for testing and troubleshooting in the early phase of development.

Cheers, Daniel