Ceph

- rip out current logging
- keep two copies of the counter vectors
- query via unix domain socket
- on each query, provide old values, new values, and time differential. or do new values + counter diff (instead of new + old)?

we can simplify this to only dump the current values and time differential.

maybe a separate command to reset the counters just for completeness, although collectd won't need it.

i like json for output formatting. partly we shouldn't need any library here since the syntax is trivial, basically

{ "field": counter,
"field2": counter
}

We've got to be able to come up with a better name than 'profiling logger', especially now that this isn't actually logging anything!