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tracing.go
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tracing.go
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/*
Package tracing provides utilities for working with open telemetry tracing.
*/
package tracing
import (
"log"
"os"
"strings"
"go.opentelemetry.io/contrib/propagators/b3"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/exporters/jaeger"
"go.opentelemetry.io/otel/propagation"
"go.opentelemetry.io/otel/sdk/resource"
tracesdk "go.opentelemetry.io/otel/sdk/trace"
semconv "go.opentelemetry.io/otel/semconv/v1.10.0"
)
/*
Open Telemetry tracing with Gin:
1) Initialize the tracing (see main.go)
2) Enable trace propagation (see tracePropagation below)
3) Use handler middleware (see main.go)
import "go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
router.Use(otelgin.Middleware("virtual-service"))
4) For http client, create a Request from Context (see backend.go)
newCtx, span := b.tracer.Start(ctx, "backendHTTP.fetch")
req, errReq := http.NewRequestWithContext(newCtx, "GET", u, nil)
client := http.Client{Transport: otelhttp.NewTransport(http.DefaultTransport)}
resp, errGet := client.Do(req)
*/
// TracerProvider creates a trace provider.
// Service name precedence from higher to lower:
// 1. OTEL_SERVICE_NAME=mysrv
// 2. OTEL_RESOURCE_ATTRIBUTES=service.name=mysrv
// 3. defaultService="mysrv"
func TracerProvider(defaultService, url string) (*tracesdk.TracerProvider, error) {
log.Printf("tracerProvider: service=%s collector=%s", defaultService, url)
// Create the Jaeger exporter
exp, err := jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(url)))
if err != nil {
return nil, err
}
var rsrc *resource.Resource
if defaultService == "" || hasServiceEnvVar() {
rsrc = resource.NewWithAttributes(
semconv.SchemaURL,
//attribute.String("environment", environment),
//attribute.Int64("ID", id),
)
} else {
rsrc = resource.NewWithAttributes(
semconv.SchemaURL,
semconv.ServiceNameKey.String(defaultService),
//attribute.String("environment", environment),
//attribute.Int64("ID", id),
)
}
tp := tracesdk.NewTracerProvider(
// Always be sure to batch in production.
tracesdk.WithBatcher(exp),
// Record information about this application in a Resource.
tracesdk.WithResource(rsrc),
)
return tp, nil
}
func hasServiceEnvVar() bool {
const me = "hasServiceEnvVar"
svc := os.Getenv("OTEL_SERVICE_NAME")
if strings.TrimSpace(svc) != "" {
log.Printf("%s: found OTEL_SERVICE_NAME=%s", me, svc)
return true
}
attrs := os.Getenv("OTEL_RESOURCE_ATTRIBUTES")
fields := strings.FieldsFunc(attrs, func(c rune) bool { return c == ',' })
for _, f := range fields {
key, val, _ := strings.Cut(f, "=")
if key == "service.name" {
log.Printf("%s: found OTEL_RESOURCE_ATTRIBUTES: %s=%s",
me, key, val)
return true
}
}
return false
}
// TracePropagation enables trace propagation.
func TracePropagation() {
// In order to propagate trace context over the wire, a propagator must be registered with the OpenTelemetry API.
// https://opentelemetry.io/docs/instrumentation/go/manual/
//otel.SetTextMapPropagator(propagation.TraceContext{})
otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
b3.New(b3.WithInjectEncoding(b3.B3MultipleHeader)),
//propagation.Baggage{},
//propagation.TraceContext{},
//ot.OT{},
))
}