diff --git a/prometheus/promhttp/option.go b/prometheus/promhttp/option.go index af7403df4..5d4383aa1 100644 --- a/prometheus/promhttp/option.go +++ b/prometheus/promhttp/option.go @@ -66,9 +66,9 @@ func WithExtraMethods(methods ...string) Option { }) } -// WithExemplarFromContext adds allows to put a hook to all counter and histogram metrics. -// If the hook function returns non-nil labels, exemplars will be added for that request, otherwise metric -// will get instrumented without exemplar. +// WithExemplarFromContext allows to inject function that will get exemplar from context that will be put to counter and histogram metrics. +// If the function returns nil labels or the metric does not support exemplars, no exemplar will be added (noop), but +// metric will continue to observe/increment. func WithExemplarFromContext(getExemplarFn func(requestCtx context.Context) prometheus.Labels) Option { return optionApplyFunc(func(o *options) { o.getExemplarFn = getExemplarFn