This takes our current config payload from 4700 bytes to 1700. The goal
is to reduce zookeeper network load during config changes as well as app
restarts during deploys.
Ok, now I'm getting some angst in my commit messages like my
predecessors had. I understand now. It's a terrible burden. Why must
the calendar progress? Why must numbers increment? The world is
forever turning.
The future is here.
It is 2014.
The dynamic configuration system has two components: the app, which
reads, and the writer script. The latter is meant for use by humans, and
converts a [live_config] section of the INI file into JSON for storage
in ZooKeeper. The app will read this data on startup and place a watch
on the node to be notified, by ZooKeeper, of changes. This means that
running the writer script with new data will automatically propagate the
changes to every app very quickly, without restart.
The writer script relies on a human-entered password to authenticate
with ZooKeeper. The reddit app uses a different set of credentials
(specified in the INI file) to obtain read-only access to the
configuration data.
Also adds a new "live_config" spec to reddit and plugins. This spec is
parsed at write-time only and the parsed values are stored as JSON in
ZooKeeper.
