metrics-clojure / docs / source / gauges.rst

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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 ...)))

.. _defgauge:

You can also use the ``defgauge`` macro to create a gauge and bind it to a var
in one concise, easy step::

    (use '[metrics.gauges :only (defgauge)])

    (defgauge files-open
      (return-number-of-files-open ...))

``defgauge`` can take a body of statements like ``gauge`` or a function like

All the ``def[metric]`` macros do some :ref:`magic <desugaring>` to the metric
title to make it easier to define.


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)