OpenTelemetry

Learn the basics of the OpenTelemetry SDK in Go.

OpenTelemetry

OpenTelemetry (OTel) is an open standard for collecting traces, metrics and logs in a vendor-neutral way. You write code once against the OTel API; data is sent with an exporter to any backend such as Jaeger, Grafana Tempo or Datadog.

tracer := otel.Tracer("siparis-servisi")
ctx, span := tracer.Start(ctx, "SiparisOlustur")
defer span.End()
span.SetAttributes(attribute.Int("urun_sayisi", 3))

SDK setup and auto-instrumentation

At program start a TracerProvider is set up and made global; on exit Shutdown flushes buffered spans. Ready-made packages such as otelhttp trace HTTP servers and clients automatically:

handler := otelhttp.NewHandler(mux, "api")
client := http.Client{Transport: otelhttp.NewTransport(http.DefaultTransport)}

This way opening a span per request and carrying the traceparent header happen on their own.

Exercise Span with attributes

Build an OTel-like structure: type Span struct { Ad string; Attr map[string]any } and func (s *Span) Set(k string, v any). Create a span, add "urun_sayisi" = 3 and "odeme" = "kart", and print len(s.Attr).

Show example solution

package main

import "fmt"

type Span struct {
    Ad   string
    Attr map[string]any
}

func (s *Span) Set(k string, v any) {
    if s.Attr == nil {
        s.Attr = map[string]any{}
    }
    s.Attr[k] = v
}

func main() {
    s := &Span{Ad: "SiparisOlustur"}
    s.Set("urun_sayisi", 3)
    s.Set("odeme", "kart")
    fmt.Println(len(s.Attr))
}

Test yourself

What changes when switching the backend from Jaeger to Tempo?
- The Go version
- The database
- Only the exporter setup
- All span code
Show answer

Only the exporter setup — Application code depends on the OTel API; the backend difference stays in the SDK setup's exporter.

Add an attribute

span.____(attribute.String("kullanici", id))

Show answer

span.SetAttributes(attribute.String("kullanici", id))

OTel parts

API

Interface the code uses
SDK

Sampling and processing
Exporter

Sends to the backend
otelhttp

Automatic HTTP tracing

Next lesson: Health check

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