Macro gauge 

macro_rules! gauge {
    ($name:literal @b : $value:expr $(, $tag:literal => $tv:expr)* $(,)?) => { ... };
    ($name:literal : $value:expr $(, $tag:literal => $tv:expr)* $(,)?) => { ... };
}

Emits a gauge metric.

Syntax

use objectstore_metrics::gauge;

gauge!("name": 1.0_f64);
gauge!("name"@b: 1024_u64);
gauge!("name": 1.0_f64, "tag" => "value");

The @b unit annotation converts via as f64 (identity for byte counts).