Code review comment for lp:~openerp-dev/openobject-server/6.1-gunicorn-signaling-vmt

My latest comment is satisfied now.

Description of the patch:

This adds a simple signaling scheme between OpenERP server instances, but also between processes (managed by, say, gunicorn). The signaling is done through the database by using two PostgreSQL sequences: one for registry invalidation, and one for caches invalidation.

The former case happens when installing a new module, the later when an tools.ormcache is cleared.

The idea is to keep inside each process a value (one per signal) provided by the db. Whenever a registry has been changed, or a cache has been cleared inside a process, the value in database is incremented. Also, whenever a process notices its internal value and the database are out of sync, its registry or caches are reloaded/cleared. Each process tests its internal values against the database at the beginning of every request handling.