Flamework assumes a federated model with all the various user data spread across a series of databases,
or "clusters". For each cluster there are a series of corresponding helper functions defined in lib_db.php.
By default Flamework does not require that it be run under a fully-federated
database system. It takes advantage of the ability to run in "poor man's
federated" mode which causes the database libraries to act as though there are
multiple database clusters when there's only really one. Specifically, all the
various databases are treated as though they live in the db_main
cluster. The goal is to enable (and ensure) that when a given installation of
a Flamework project outgrows a simple one or two machine setup that it can easily
be migrated to a more robust system with a minimum of fuss.
As of this writing Flamework defines/expects the following clusters:
- db_main
This is the database cluster where user accounts and other lookup-style database tables live.
- db_users
These are the federated tables, sometimes called "shards". This is where the bulk of the data in Dotspotting is stored because it can be spread out, in smaller chunks, across a whole bunch of databases rather than a single monolithic monster database that becomes a single point of failure and it just generally a nuisance to maintain.
- db_tickets
One of the things about storing federated user data is that from time to time you may need to "re-balance"
your shards, for example moving all of a user's data from shard #5 to shard #23. That means you can no longer
rely on an individual database to generate auto-incrementing unique IDs because each database shard creates
those IDs in isolation and if you try to move a dot, for example, with ID 123 to a shard with another dot
that already has the same ID everything will break and there will be tears.
The way around this is to use "ticketing" servers whose only job is to sit around and assign unique IDs.
A discussion of ticketing servers is outside the scope of this document but Kellan wrote a good blog post
about the subject
if you're interested in learning more. Which is a long way of saying: Flamework uses tickets and they come
from the db_tickets cluster.