fix collection

prometheus/collector_metric.go

@@ -13,6 +13,10 @@
 
 package prometheus
 
+import (
+	"log"
+)
+
 const (
 	metricsBufferSize = 1024 * 8
 )
@@ -38,20 +42,26 @@ func NewMetaMetricsCollector() *MetaMetrics {
 }
 
 func (m *MetaMetrics) Add(metric Metric) {
-	m.cache <- metric
+	select {
+	case m.cache <- metric:
+	default:
+		log.Println("MetaMetrics blocked")
+	}
+
 }
 
 func (m *MetaMetrics) Describe(ch chan<- *Desc) {
 	ch <- m.desc
 }
 
 func (m *MetaMetrics) Collect(ch chan<- Metric) {
+collect:
 	for {
 		select {
 		case metric := <-m.cache:
 			ch <- metric
 		default:
-			break
+			break collect
 		}
 	}
 }

prometheus/registry.go

@@ -447,9 +447,9 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 
 	wg.Add(goroutineBudget)
 
+	var metaMetricCollector Collector
 	collectWorker := func() {
 		for {
-			var metaMetricCollector Collector
 			select {
 			case collector := <-checkedCollectors:
 				if _, ok := collector.(*MetaMetrics); ok {
@@ -460,9 +460,6 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 			case collector := <-uncheckedCollectors:
 				collector.Collect(uncheckedMetricChan)
 			default:
-				if metaMetricCollector != nil {
-					metaMetricCollector.Collect(checkedMetricChan)
-				}
 				return
 			}
 			wg.Done()
@@ -477,6 +474,9 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 	// are collected.
 	go func() {
 		wg.Wait()
+		if metaMetricCollector != nil {
+			metaMetricCollector.Collect(checkedMetricChan)
+		}
 		close(checkedMetricChan)
 		close(uncheckedMetricChan)
 	}()