zero/telemetry: internal envoy stats scraper and metrics producer (#5136)

internal/zero/telemetry/metrics_producer.go

@@ -0,0 +1,54 @@
+package telemetry
+
+import (
+	"context"
+	"sync/atomic"
+
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+
+	"github.com/pomerium/pomerium/internal/log"
+)
+
+// metricsProducer is a wrapper around a metric producer that can be enabled or disabled
+type metricsProducer[P metric.Producer] struct {
+	enabled  atomic.Bool
+	name     string
+	producer P
+}
+
+func newMetricsProducer[P metric.Producer](name string, p P) *metricsProducer[P] {
+	return &metricsProducer[P]{
+		name:     name,
+		producer: p,
+	}
+}
+
+// Produce wraps the underlying producer's Produce method and logs any errors,
+// to prevent the error from blocking the export of other metrics.
+// also checks if the producer is enabled before producing metrics
+func (p *metricsProducer[P]) Produce(ctx context.Context) ([]metricdata.ScopeMetrics, error) {
+	if enabled := p.enabled.Load(); !enabled {
+		return nil, nil
+	}
+
+	data, err := p.producer.Produce(ctx)
+	if err != nil {
+		// we do not return the error here, as we do not want to block the export of other metrics
+		log.Error(ctx).Err(err).Str("producer", p.name).Msg("failed to produce metrics")
+		return nil, nil
+	}
+	return data, nil
+}
+
+func (p *metricsProducer[P]) SetEnabled(v bool) {
+	p.enabled.Store(v)
+}
+
+func (p *metricsProducer[P]) Name() string {
+	return p.name
+}
+
+func (p *metricsProducer[P]) Producer() P {
+	return p.producer
+}