tracing.go

package tracing

/*
Copyright 2022 The k8gb Contributors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Generated by GoLic, for more details see: https://github.com/AbsaOSS/golic
*/

import (
	"context"
	"fmt"
	"math"

	"github.com/rs/zerolog"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.6.1"
	"go.opentelemetry.io/otel/trace"
)

const (
	instrumentationName = "github.com/k8gb-io/k8gb"
)

type Settings struct {
	Enabled       bool
	Endpoint      string
	SamplingRatio float64
	Commit        string
	AppVersion    string
}

func SetupTracing(ctx context.Context, cfg Settings, log *zerolog.Logger) (func(), trace.Tracer) {
	if !cfg.Enabled {
		log.Info().Msg("OTLP tracing is disabled")
		//nolint:staticcheck
		return func() {}, trace.NewNoopTracerProvider().Tracer(instrumentationName)
	}
	log.Info().Msg("OTLP tracing is ON")
	client := otlptracehttp.NewClient(
		otlptracehttp.WithEndpoint(cfg.Endpoint),
		otlptracehttp.WithInsecure(),
	)
	exporter, err := otlptrace.New(ctx, client)
	if err != nil {
		log.Err(err).Msg("creating OTLP trace exporter")
	}
	var samplerOption sdktrace.TracerProviderOption
	eps := 0.0001
	if math.Abs(cfg.SamplingRatio-1.0) > eps { // not equal 1.0 (IEEE 754)
		samplerOption = sdktrace.WithSampler(sdktrace.TraceIDRatioBased(cfg.SamplingRatio))
		log.Info().Msg(fmt.Sprintf("Tracing: sampling ratio is set to '%.3f'", cfg.SamplingRatio))
	} else {
		log.Info().Msg("Tracing: sampling ratio is not specified, using AlwaysSample")
		samplerOption = sdktrace.WithSampler(sdktrace.AlwaysSample())
	}

	tracerProvider := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exporter),
		sdktrace.WithResource(newResource(cfg.Commit)),
		samplerOption,
	)
	otel.SetTracerProvider(tracerProvider)
	tracer := tracerProvider.Tracer(
		instrumentationName,
		trace.WithInstrumentationVersion(cfg.AppVersion),
		trace.WithSchemaURL(semconv.SchemaURL))

	return func() {
		if err := tracerProvider.Shutdown(ctx); err != nil {
			log.Err(err).Msg("stopping tracer provider")
		}
	}, tracer
}

func newResource(commit string) *resource.Resource {
	return resource.NewWithAttributes(
		semconv.SchemaURL,
		semconv.ServiceNameKey.String("k8gb"),
		semconv.ServiceVersionKey.String(commit),
	)
}