Gauges are used to measure the instantaneous value of something.
Create your gauge:
(use '[metrics.gauges :only (gauge)]) (def files-open (gauge "files-open" (return-number-of-files-open ...)))
That's it. Pretty simple.
gauge is a macro. If you need a function instead you can use gauge-fn, but you have to pass it a function, not just a body:
(use '[metrics.gauges :only (gauge-fn)]) (def files-open (gauge-fn "files-open" #(return-number-of-files-open ...)))
There is no writing. Gauges execute the form(s) (or function) you passed when creating them every time they're read. You don't need to do anything else.
There's only one way to get data from a gauge.
You can read the value of a gauge at any time with value:
(use '[metrics.gauges :only (value)]) (value files-open)