On 2017-05-11T12:47:21, Sage Weil <sage@xxxxxxxxxxxx> wrote:
> > I would love to see a mgr module for prometheus integration!
> Me too! It might make more sense to do it in C++ than python, though, for
> performance reasons.
I'm leaning the other way. (Disclaimer: I started this dialogue
internally and was originally thinking of putting it into ceph-mgr.)
prometheus implements a pull model for time series data / metrics. For
those to be pull-able from ceph-mgr, either ceph-mgr needs to pull
itself, or daemons stream to it. Clearly it can't pull something that's
not there.
Both have slightly different issues with aligning the periods/intervals.
Prometheus also can scale through polling via several instances; if we
pull everything from ceph-mgr, that is a single chokepoint.
Further, if ceph-mgr were to pull data from individual daemons - why not
have prometheus do this directly? What benefit does this additional
indirection step offer?
If we have rather detailed stats per daemon, ceph-mgr would either relay
them on as-is (pure overhead), or aggregate them - and likely not
aggregate them as well/flexibly as Prometheus would allow via PQL.
Now, that's not to say that ceph-mgr would not benefit from a Prometheus
interface! I could easily see ceph-mgr have stats of its own that are
worth monitoring, and we should make it easy to export those.
So, in short, I believe an easy way to export per-daemon metrics is
desirable. ceph-mgr might choose to pull these in as well if it has a
use for them, but I think Prometheus would best attach to the daemons
directly too.
Regards,
Lars
--
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde
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