Create metrics.Factory adapter for OTEL Metrics (#5661)

**Which problem is this PR solving?**

This PR addresses a part of the issue [#5633
](#5633)

**Description of the changes**
This is a Draft PR to bridge the OTEL Metrics instead of using Internal
Metrics to minimize code changes.
**How was this change tested?**

The changes were tested by running the following command:

```bash
make test
```

**Checklist**

- [x] I have read
[CONTRIBUTING_GUIDELINES.md](https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md)
- [x] I have signed all commits
- [x] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully
  - `for jaeger: make lint test`
  - `for jaeger-ui: yarn lint` and `yarn test`

---------

Signed-off-by: Wise-Wizard <[email protected]>
Signed-off-by: Saransh Shankar <[email protected]>
Signed-off-by: Yuri Shkuro <[email protected]>
Co-authored-by: Yuri Shkuro <[email protected]>
Co-authored-by: Yuri Shkuro <[email protected]>

internal/metrics/benchmark_test.go

@@ -0,0 +1,113 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package benchmark_test
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/require"
+	promExporter "go.opentelemetry.io/otel/exporters/prometheus"
+	"go.opentelemetry.io/otel/sdk/metric"
+
+	"github.com/jaegertracing/jaeger/internal/metrics/otelmetrics"
+	prom "github.com/jaegertracing/jaeger/internal/metrics/prometheus"
+	"github.com/jaegertracing/jaeger/pkg/metrics"
+	"github.com/jaegertracing/jaeger/pkg/testutils"
+)
+
+func TestMain(m *testing.M) {
+	testutils.VerifyGoLeaks(m)
+}
+
+func setupPrometheusFactory() metrics.Factory {
+	reg := prometheus.NewRegistry()
+	return prom.New(prom.WithRegisterer(reg))
+}
+
+func setupOTELFactory(b *testing.B) metrics.Factory {
+	registry := prometheus.NewRegistry()
+	exporter, err := promExporter.New(promExporter.WithRegisterer(registry))
+	require.NoError(b, err)
+	meterProvider := metric.NewMeterProvider(
+		metric.WithReader(exporter),
+	)
+	return otelmetrics.NewFactory(meterProvider)
+}
+
+func benchmarkCounter(b *testing.B, factory metrics.Factory) {
+	counter := factory.Counter(metrics.Options{
+		Name: "test_counter",
+		Tags: map[string]string{"tag1": "value1"},
+	})
+
+	for i := 0; i < b.N; i++ {
+		counter.Inc(1)
+	}
+}
+
+func benchmarkGauge(b *testing.B, factory metrics.Factory) {
+	gauge := factory.Gauge(metrics.Options{
+		Name: "test_gauge",
+		Tags: map[string]string{"tag1": "value1"},
+	})
+
+	for i := 0; i < b.N; i++ {
+		gauge.Update(1)
+	}
+}
+
+func benchmarkTimer(b *testing.B, factory metrics.Factory) {
+	timer := factory.Timer(metrics.TimerOptions{
+		Name: "test_timer",
+		Tags: map[string]string{"tag1": "value1"},
+	})
+
+	for i := 0; i < b.N; i++ {
+		timer.Record(100)
+	}
+}
+
+func benchmarkHistogram(b *testing.B, factory metrics.Factory) {
+	histogram := factory.Histogram(metrics.HistogramOptions{
+		Name: "test_histogram",
+		Tags: map[string]string{"tag1": "value1"},
+	})
+
+	for i := 0; i < b.N; i++ {
+		histogram.Record(1.0)
+	}
+}
+
+func BenchmarkPrometheusCounter(b *testing.B) {
+	benchmarkCounter(b, setupPrometheusFactory())
+}
+
+func BenchmarkOTELCounter(b *testing.B) {
+	benchmarkCounter(b, setupOTELFactory(b))
+}
+
+func BenchmarkPrometheusGauge(b *testing.B) {
+	benchmarkGauge(b, setupPrometheusFactory())
+}
+
+func BenchmarkOTELGauge(b *testing.B) {
+	benchmarkGauge(b, setupOTELFactory(b))
+}
+
+func BenchmarkPrometheusTimer(b *testing.B) {
+	benchmarkTimer(b, setupPrometheusFactory())
+}
+
+func BenchmarkOTELTimer(b *testing.B) {
+	benchmarkTimer(b, setupOTELFactory(b))
+}
+
+func BenchmarkPrometheusHistogram(b *testing.B) {
+	benchmarkHistogram(b, setupPrometheusFactory())
+}
+
+func BenchmarkOTELHistogram(b *testing.B) {
+	benchmarkHistogram(b, setupOTELFactory(b))
+}

internal/metrics/otelmetrics/counter.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package otelmetrics
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/metric"
+)
+
+type otelCounter struct {
+	counter  metric.Int64Counter
+	fixedCtx context.Context
+	option   metric.AddOption
+}
+
+func (c *otelCounter) Inc(value int64) {
+	c.counter.Add(c.fixedCtx, value, c.option)
+}

internal/metrics/otelmetrics/factory.go

@@ -0,0 +1,133 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package otelmetrics
+
+import (
+	"context"
+	"log"
+	"strings"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+
+	"github.com/jaegertracing/jaeger/pkg/metrics"
+)
+
+type otelFactory struct {
+	meter      metric.Meter
+	scope      string
+	separator  string
+	normalizer *strings.Replacer
+	tags       map[string]string
+}
+
+func NewFactory(meterProvider metric.MeterProvider) metrics.Factory {
+	return &otelFactory{
+		meter:      meterProvider.Meter("jaeger-v2"),
+		separator:  ".",
+		normalizer: strings.NewReplacer(" ", "_", ".", "_", "-", "_"),
+		tags:       make(map[string]string),
+	}
+}
+
+func (f *otelFactory) Counter(opts metrics.Options) metrics.Counter {
+	name := f.subScope(opts.Name)
+	counter, err := f.meter.Int64Counter(name)
+	if err != nil {
+		log.Printf("Error creating OTEL counter: %v", err)
+		return metrics.NullCounter
+	}
+	return &otelCounter{
+		counter:  counter,
+		fixedCtx: context.Background(),
+		option:   attributeSetOption(f.mergeTags(opts.Tags)),
+	}
+}
+
+func (f *otelFactory) Gauge(opts metrics.Options) metrics.Gauge {
+	name := f.subScope(opts.Name)
+	gauge, err := f.meter.Int64Gauge(name)
+	if err != nil {
+		log.Printf("Error creating OTEL gauge: %v", err)
+		return metrics.NullGauge
+	}
+
+	return &otelGauge{
+		gauge:    gauge,
+		fixedCtx: context.Background(),
+		option:   attributeSetOption(f.mergeTags(opts.Tags)),
+	}
+}
+
+func (f *otelFactory) Histogram(opts metrics.HistogramOptions) metrics.Histogram {
+	name := f.subScope(opts.Name)
+	histogram, err := f.meter.Float64Histogram(name)
+	if err != nil {
+		log.Printf("Error creating OTEL histogram: %v", err)
+		return metrics.NullHistogram
+	}
+
+	return &otelHistogram{
+		histogram: histogram,
+		fixedCtx:  context.Background(),
+		option:    attributeSetOption(f.mergeTags(opts.Tags)),
+	}
+}
+
+func (f *otelFactory) Timer(opts metrics.TimerOptions) metrics.Timer {
+	name := f.subScope(opts.Name)
+	timer, err := f.meter.Float64Histogram(name, metric.WithUnit("s"))
+	if err != nil {
+		log.Printf("Error creating OTEL timer: %v", err)
+		return metrics.NullTimer
+	}
+	return &otelTimer{
+		histogram: timer,
+		fixedCtx:  context.Background(),
+		option:    attributeSetOption(f.mergeTags(opts.Tags)),
+	}
+}
+
+func (f *otelFactory) Namespace(opts metrics.NSOptions) metrics.Factory {
+	return &otelFactory{
+		meter:      f.meter,
+		scope:      f.subScope(opts.Name),
+		separator:  f.separator,
+		normalizer: f.normalizer,
+		tags:       f.mergeTags(opts.Tags),
+	}
+}
+
+func (f *otelFactory) subScope(name string) string {
+	if f.scope == "" {
+		return f.normalize(name)
+	}
+	if name == "" {
+		return f.normalize(f.scope)
+	}
+	return f.normalize(f.scope + f.separator + name)
+}
+
+func (f *otelFactory) normalize(v string) string {
+	return f.normalizer.Replace(v)
+}
+
+func (f *otelFactory) mergeTags(tags map[string]string) map[string]string {
+	merged := make(map[string]string)
+	for k, v := range f.tags {
+		merged[k] = v
+	}
+	for k, v := range tags {
+		merged[k] = v
+	}
+	return merged
+}
+
+func attributeSetOption(tags map[string]string) metric.MeasurementOption {
+	attributes := make([]attribute.KeyValue, 0, len(tags))
+	for k, v := range tags {
+		attributes = append(attributes, attribute.String(k, v))
+	}
+	return metric.WithAttributes(attributes...)
+}