Preserve zero-success series in PromQL ratios

A direct PromQL success/total ratio disappears when success is zero because the numerator series may be absent, even while failed attempts make the denominator nonzero. Dashboards then show No Data in the worst operational state. Preserve the denominator’s label set by expressing success as one minus non-success/total, or union a zero-valued numerator aligned to the denominator; still guard zero traffic separately. Leave genuinely traffic-free groups absent when that distinction is useful.

Applies when: Grafana panels or alerts divide a sparse success counter by an attempt counter. Keywords: PromQL Grafana ratio absent series zero success dashboard