Macro histogram

macro_rules! histogram {
    ($metric:ident $(. $suffixes:ident)*  = $metric_value:expr $(, $attrs:ident=$values:expr)*) => { ... };
}

Adds an additional value to the distribution of the named histogram with the given attributes.

The increment may only be an i64 or f64. You must not mix types for the same metric.

histogram!(spin.metric_name = 1.5, metric_attribute = "value");