We experimented with different async DB approaches, but settled on
synchronous at FriendFeed because generally if our DB queries were
backlogging our requests, our backends couldn't scale to the load
anyway. Things that were slow enough were abstracted to separate
backend services which we fetched asynchronously via the async HTTP
module.
I may open source the async MySQL client I wrote, but I am still
skeptical of the long term value given the code complexity it
introduces.
Bret
Erm, so if things are fast it doesn't matter and if things are slow you should write a whole new service, put a HTTP interface into it and use that? Not sure I buy that :)
Disclaimer: I wrote an async DB module for Twisted/PostgreSQL and it did not turn out to be all that complex.
There's async libraries here: https://github.com/facebook/tornado/wiki/Links - You can get just about any db except MySQL. There's ones for Couch, Mongo, HBase, a bunch of other No-SQLs and Psycopg (PostGres).
Also, Tornado is now introducing some kind of interface to Twisted's event loop, which does have everything ported.
Bret just doesn't seem to want async My-SQL in the main code base.
From Wikipedia: [FriendFeed] had on average one million monthly visitors ... [and] was bought for $15 million in cash, and $32.5 million in Facebook stock.
I figure after the first million users, your embarrassingly parellel app server layer is not your bottleneck, it's getting the database to scale.
