diff --git a/prometheus/registry.go b/prometheus/registry.go index 383a7f594..9c9fc9566 100644 --- a/prometheus/registry.go +++ b/prometheus/registry.go @@ -407,6 +407,14 @@ func (r *Registry) MustRegister(cs ...Collector) { // Gather implements Gatherer. func (r *Registry) Gather() ([]*dto.MetricFamily, error) { + r.mtx.RLock() + + if len(r.collectorsByID) == 0 && len(r.uncheckedCollectors) == 0 { + // Fast path. + r.mtx.RUnlock() + return nil, nil + } + var ( checkedMetricChan = make(chan Metric, capMetricChan) uncheckedMetricChan = make(chan Metric, capMetricChan) @@ -416,7 +424,6 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) { registeredDescIDs map[uint64]struct{} // Only used for pedantic checks ) - r.mtx.RLock() goroutineBudget := len(r.collectorsByID) + len(r.uncheckedCollectors) metricFamiliesByName := make(map[string]*dto.MetricFamily, len(r.dimHashesByName)) checkedCollectors := make(chan Collector, len(r.collectorsByID))