def gauge(stat, value, rate=1, buf=None, rate_applied=False):
    """
        Update a gauge value.

        ``stat`` is the name of the metric to record and ``value`` is
        the new gauge value. A gauge represents a persistent value
        such as a pool size. Because gauges from different machines
        often conflict, a suffix is usually applied to gauge names;
        this may be done manually or with `MetricMod`.
        """
