We moved from sending statsd metrics to hosted graphite to sending to
one that is running on the paas. Therefore we no longer need to send
statsd metrics to a particular prefix at the statsd app as it is only
receiving statsd metrics from our apps (not other users like would have
been the case with HostedGraphite).
This should change no behaviour as the only place the environment
variable was being used was in the gunicorn config and it was an empty
string which is the default behaviour anyway as per:
https://docs.gunicorn.org/en/stable/settings.html#statsd-prefix
All our requests identify the web server they were served with via the
`server` response header. This opens us up to potential attackers who
might be crawling the internet looking for specific versions with known
vulnerabilities. As our dependencies are open source, this doesn't
affect any targeted attacks as they can just look at our repos on
github, but this theoretically will marginally improve security.
Regardless, the header isn't useful [1], we're not the first people to
want to get rid of it, and gunicorn are in the process of at least
amending it to remove the version information [2].
This shouldn't have any impact on us, though an empty string will be
passed through to debug information in event of a crash. That's fine
though, as we already know what version we're running.
[1] https://www.fastly.com/blog/headers-we-dont-want
[2] https://github.com/benoitc/gunicorn/issues/825
- Gunicorn can give us some interestings stats about what it is doing
that might prove useful when trying to work out the
gunicorn/eventlet/sqlalchemy kind of bottlenecking issues
- We already ship these env vars to the app so this is a pretty easy
change to make
- Uses statsd which is UDP so it shouldn't have any performance impact
on gunicorn
At the same time, decrease the number of workers from 5 to 4.
Effect on max db connections will be the same - although with a higher
"resting" number of connections.
Before:
12 (instances) * 5 (workers) * 20 (10 permanent + 10 overflow) = 1200
After:
12 (instances) * 4 (workers) * 25 (15 permanent + 10 overflow) = 1200
