Documentation, including a list of metrics reported and their semantics,
is in the Admin Guide in a new section, "Reporting Metrics to StatsD".
An optional "metric prefix" may be configured which will be prepended to
every metric name sent to StatsD.
Here is the rationale for doing a deep integration like this versus only
sending metrics to StatsD in middleware. It's the only way to report
some internal activities of Swift in a real-time manner. So to have one
way of reporting to StatsD and one place/style of configuration, even
some things (like, say, timing of PUT requests into the proxy-server)
which could be logged via middleware are consistently logged the same
way (deep integration via the logger delegate methods).
When log_statsd_host is configured, get_logger() injects a
swift.common.utils.StatsdClient object into the logger as
logger.statsd_client. Then a set of delegate methods on LogAdapter
either pass through to the StatsdClient object or become no-ops. This
allows StatsD logging to look like:
self.logger.increment('some.metric.here')
and do the right thing in all cases and with no messy conditional logic.
I wanted to use the pystatsd module for the StatsD client, but the
version on PyPi is lagging the git repo (and is missing both the prefix
functionality and timing_since() method). So I wrote my
swift.common.utils.StatsdClient. The interface is the same as
pystatsd.Client, but the code was written from scratch. It's pretty
simple, and the tests I added cover it. This also frees Swift from an
optional dependency on the pystatsd module, making this feature easier
to enable.
There's test coverage for the new code and all existing tests continue
to pass.
Refactored out _one_audit_pass() method in swift/account/auditor.py and
swift/container/auditor.py.
Fixed some misc. PEP8 violations.
Misc test cleanups and refactorings (particularly the way "fake logging"
is handled).
Change-Id: Ie968a9ae8771f59ee7591e2ae11999c44bfe33b2
