I'd implemented stats gathering hooks in the helper a while back.
Brian did the same without reference to my changes. This reconciles
those two changes, encompassing all the stats in both changes,
implemented through the stats_provider interface.
this also provide templates for all 10 helper graphs in the
tahoe-stats munin plugin.
having changed tahoe-stats to not report data series if there was no recent
data recorded for a node, I wound up making it hide the data series. this
change causes it to report all data series for which stats exist in the
'config' phase, so that they show up, but only report actual data if the
stats are recent, so that they show up as missing if the node is not
reporting stats currently
if a node fails to report stats, the natural thing to do in re munin is to
supress the data for that data series. the previous tahoe-stats would output
whatever data was present in the stats_gatherer's stats.pickle, regardless of
how old.
this change means that if the gatherer hasn't received data within the last
5 min, then no data is reported to munin for that node.
We have a desire to collect runtime statistics from multiple nodes primarily
for server monitoring purposes. This implements a simple implementation of
such a system, as a skeleton to build more sophistication upon.
Each client now looks for a 'stats_gatherer.furl' config file. If it has
been configured to use a stats gatherer, then it instantiates internally
a StatsProvider. This is a central place for code which wishes to offer
stats up for monitoring to report them to, either by calling
stats_provider.count('stat.name', value) to increment a counter, or by
registering a class as a stats producer with sp.register_producer(obj).
The StatsProvider connects to the StatsGatherer server and provides its
provider upon startup. The StatsGatherer is then responsible for polling
the attached providers periodically to retrieve the data provided.
The provider queries each registered producer when the gatherer queries
the provider. Both the internal 'counters' and the queried 'stats' are
then reported to the gatherer.
This provides a simple gatherer app, (c.f. make stats-gatherer-run)
which prints its furl and listens for incoming connections. Once a
minute, the gatherer polls all connected providers, and writes the
retrieved data into a pickle file.
Also included is a munin plugin which knows how to read the gatherer's
stats.pickle and output data munin can interpret. this plugin,
tahoe-stats.py can be symlinked as multiple different names within
munin's 'plugins' directory, and inspects argv to determine which
data to display, doing a lookup in a table within that file.
It looks in the environment for 'statsfile' to determine the path to
the gatherer's stats.pickle. An example plugins-conf.d file is
provided.
