add otel module based on uptrace-go

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

otel/metrics.go

@@ -0,0 +1,77 @@
+package otel
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/contrib/bridges/prometheus"
+	runtimemetrics "go.opentelemetry.io/contrib/instrumentation/runtime"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp"
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+func configureMetrics(ctx context.Context, conf *config) *sdkmetric.MeterProvider {
+	opts := conf.metricOptions
+	if res := conf.newResource(); res != nil {
+		opts = append(opts, sdkmetric.WithResource(res))
+	}
+
+	for _, dsn := range conf.dsn {
+		dsn, err := ParseDSN(dsn)
+		if err != nil {
+			log.WithError(err).Error("ParseDSN failed")
+			continue
+		}
+
+		exp, err := otlpmetricClient(ctx, conf, dsn)
+		if err != nil {
+			log.WithError(err).Warn("otlpmetricClient")
+			continue
+		}
+
+		ropts := []sdkmetric.PeriodicReaderOption{sdkmetric.WithInterval(5 * time.Second)}
+		if conf.metricPrometheusBridge {
+			ropts = append(ropts, sdkmetric.WithProducer(prometheus.NewMetricProducer()))
+		}
+		opts = append(opts, sdkmetric.WithReader(sdkmetric.NewPeriodicReader(exp, ropts...)))
+	}
+
+	provider := sdkmetric.NewMeterProvider(opts...)
+	otel.SetMeterProvider(provider)
+
+	if err := runtimemetrics.Start(); err != nil {
+		log.WithError(err).Error("runtimemetrics.Start failed")
+	}
+
+	return provider
+}
+
+func otlpmetricClient(ctx context.Context, conf *config, dsn *DSN) (sdkmetric.Exporter, error) {
+	options := []otlpmetrichttp.Option{
+		otlpmetrichttp.WithEndpoint(dsn.OTLPHttpEndpoint()),
+		otlpmetrichttp.WithHeaders(dsn.Headers()),
+		otlpmetrichttp.WithCompression(otlpmetrichttp.GzipCompression),
+		otlpmetrichttp.WithTemporalitySelector(preferDeltaTemporalitySelector),
+	}
+
+	if conf.tlsConf != nil {
+		options = append(options, otlpmetrichttp.WithTLSClientConfig(conf.tlsConf))
+	} else if dsn.Scheme == "http" {
+		options = append(options, otlpmetrichttp.WithInsecure())
+	}
+
+	return otlpmetrichttp.New(ctx, options...)
+}
+
+func preferDeltaTemporalitySelector(kind sdkmetric.InstrumentKind) metricdata.Temporality {
+	switch kind {
+	case sdkmetric.InstrumentKindCounter,
+		sdkmetric.InstrumentKindObservableCounter,
+		sdkmetric.InstrumentKindHistogram:
+		return metricdata.DeltaTemporality
+	default:
+		return metricdata.CumulativeTemporality
+	}
+}