Summary:
This exposes metrics for the live FUSE requests (the duration
of the longest outstanding request and the number of outstanding
requests).
Because FUSE is the interface through which the user mostly interacts
with the file system they provide good metrics to judge if the perfomance
of eden is normal, or there may be an issue.
Exposing these counters this way will send them to ods, so it will not only
allow for debuging current issues, but can be used to look back at previous
problems. This data could also be used for alerting or more proactive
remediation.
Metrics are exposed per checkout to allow seeing which checkout was
having issues. This data will aggregated in `eden top` to be used as
an overall health indicator, but should more information be needed it
will be logged in ods.
Reviewed By: chadaustin
Differential Revision: D20922194
fbshipit-source-id: 16208883417acb77b62bf712cfdd9068c5420303
d850667e19