bnkamalesh/goapp

package apm

import (
    "context"
    "fmt"

    "go.opentelemetry.io/contrib/propagators/b3"
    "go.opentelemetry.io/otel"
    "go.opentelemetry.io/otel/attribute"
    "go.opentelemetry.io/otel/propagation"
    "go.opentelemetry.io/otel/sdk/resource"
    sdktrace "go.opentelemetry.io/otel/sdk/trace"
    semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
    "go.opentelemetry.io/otel/trace"
)

const environmentLabel = "environment"

// Tracer represents common wrapper on any customTracer
type Tracer struct {
    // So far no custom behavior, export all sdk for convenience
    trace.Tracer
}

// New create a global tracerProvider and a custom tracer for the application own usage
// we need both obj because tracerProvider is the way to integrate with other otel sdk
func NewTracer(ctx context.Context, opts *Options, exporter sdktrace.SpanExporter) (trace.TracerProvider, *Tracer) {
    s := &Tracer{}

    batchProcessor := sdktrace.NewBatchSpanProcessor(exporter)
    sampler := sdktrace.ParentBased(sdktrace.TraceIDRatioBased(opts.TracesSampleRate))
    tp := sdktrace.NewTracerProvider(
        sdktrace.WithSampler(sampler),
        sdktrace.WithSpanProcessor(batchProcessor),
        sdktrace.WithResource(resource.NewWithAttributes(
            semconv.SchemaURL,
            semconv.ServiceNameKey.String(opts.ServiceName),
            semconv.ServiceVersionKey.String(opts.ServiceVersion),
            attribute.String(environmentLabel, opts.Environment),
        )),
    )
    otel.SetTracerProvider(tp)

    propagator := propagation.NewCompositeTextMapPropagator(
        propagation.TraceContext{},
        b3.New(b3.WithInjectEncoding(b3.B3SingleHeader|b3.B3MultipleHeader)), // For Istio compatibility
    )
    otel.SetTextMapPropagator(propagator)

    s.Tracer = tp.Tracer(fmt.Sprintf("%s:tracer", opts.ServiceName))

    return tp, s
}