go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.70.0: NewHandler

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler in pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0
Demonstrate these symbols/APIs:
  - go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:3f4d876f09ab6b922febf20fd34473fe488a70582954f6363bd561fb71aa3404","contract":["NewHandler wraps an http.Handler with OpenTelemetry server span instrumentation.","NewHandler injects a valid SpanContext into the request context accessible by inner handlers.","NewHandler formats span name dynamically using WithSpanNameFormatter.","NewHandler skips tracing for requests excluded by WithFilter.","NewHandler records response status code on the completed server span."],"goal":"verify go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler in pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler"]},"contractCommand":["go","test","-v","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0"],"schemaVersion":1,"subject":"pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0","symbols":["go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler"],"verifierAdapter":"golang@1"}

module example.com/otelhttp-sample

go 1.26.6

require (
	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.70.0
	go.opentelemetry.io/otel/sdk v1.45.0
	go.opentelemetry.io/otel/trace v1.45.0
)

require (
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	github.com/felixge/httpsnoop v1.1.0 // indirect
	github.com/go-logr/logr v1.4.4 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	github.com/google/uuid v1.6.0 // indirect
	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
	go.opentelemetry.io/otel v1.45.0 // indirect
	go.opentelemetry.io/otel/metric v1.45.0 // indirect
	golang.org/x/sys v0.47.0 // indirect
)

github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/felixge/httpsnoop v1.1.0 h1:3YtUj32ZZkqZtt3sZZsClsymw/QDuVfpNhoA31zeORc=
github.com/felixge/httpsnoop v1.1.0/go.mod h1:Zqxgdd+1Rkcz8euOqdr7lqgCRJztwr5hp9vDSi5UZCE=
github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
github.com/go-logr/logr v1.4.4 h1:tG4xh9yMsRCAiodLVTxyrkzSZ9+o0L1Kg/+cPVcbP/8=
github.com/go-logr/logr v1.4.4/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.70.0 h1:LMuyCAyfalSjDyjdC65nK6N0zoTT63+E/u95X0JovZI=
go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.70.0/go.mod h1:085m8qbm4hgc8rZWGDEa4vmyyo2c3nPxUslYUKUIU04=
go.opentelemetry.io/otel v1.45.0 h1:pdrWmLHofpubmArBv1LgFSv1Z0Ie/ppdZzu+kUN5EeU=
go.opentelemetry.io/otel v1.45.0/go.mod h1:XZxIqPapzEYnhNSScF5DIqXhm/rYi0FzCe2XddAwZfQ=
go.opentelemetry.io/otel/metric v1.45.0 h1:7Eg1uH7CJ5cXv9is6tnBe1FI6rj1nwUdbFypRm3br/M=
go.opentelemetry.io/otel/metric v1.45.0/go.mod h1:HAPbm1nd3p1PmFH7v2dR+6BjXxw+Lq4a2+pndMAm08s=
go.opentelemetry.io/otel/sdk v1.45.0 h1:4VVSMgQ83dUgW2aoX5f6JgLvHwIvzcuLnF9lUdCSpCw=
go.opentelemetry.io/otel/sdk v1.45.0/go.mod h1:Sr40LgXV7DsKMMJMKOhUWOgMWTfAaqvm2kF0g7ilwuA=
go.opentelemetry.io/otel/sdk/metric v1.45.0 h1:oVFszMfyj1Am6s24Vtc7wBb8BKLcwepJjNEYILuiE3o=
go.opentelemetry.io/otel/sdk/metric v1.45.0/go.mod h1:vUWUxDZvu1WVRj8JA8S0AdhsPrZoDpA2DdZauIh4mDA=
go.opentelemetry.io/otel/trace v1.45.0 h1:l/mP6Uv7oNO7/TblbhpbgMidxhq1uO/rPsikOyVhxag=
go.opentelemetry.io/otel/trace v1.45.0/go.mod h1:qoJJA2xNMnxRrdISU/kLtfUH2wNeQbiv+jhs/CxI8bc=
go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package sample

import (
	"fmt"
	"net/http"

	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
	"go.opentelemetry.io/otel/trace"
)

// ServerOptions holds configurable options for creating instrumented handlers.
type ServerOptions struct {
	TracerProvider trace.TracerProvider
	Filter         otelhttp.Filter
	NameFormatter  func(operation string, r *http.Request) string
}

// WrapHandler wraps the given http.Handler with OpenTelemetry instrumentation
// using otelhttp.NewHandler with the specified operation name and options.
func WrapHandler(base http.Handler, operation string, opts ServerOptions) http.Handler {
	var otelOpts []otelhttp.Option
	if opts.TracerProvider != nil {
		otelOpts = append(otelOpts, otelhttp.WithTracerProvider(opts.TracerProvider))
	}
	if opts.Filter != nil {
		otelOpts = append(otelOpts, otelhttp.WithFilter(opts.Filter))
	}
	if opts.NameFormatter != nil {
		otelOpts = append(otelOpts, otelhttp.WithSpanNameFormatter(opts.NameFormatter))
	}
	return otelhttp.NewHandler(base, operation, otelOpts...)
}

// HelloHandler returns a simple HTTP handler that reads the active span from context
// and writes a response header and body.
func HelloHandler() http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		span := trace.SpanFromContext(r.Context())
		if span.SpanContext().IsValid() {
			w.Header().Set("X-Trace-ID", span.SpanContext().TraceID().String())
		}
		w.WriteHeader(http.StatusOK)
		_, _ = fmt.Fprint(w, "hello from instrumented handler")
	})
}

package sample_test

import (
	"context"
	"io"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"

	sample "example.com/otelhttp-sample"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	"go.opentelemetry.io/otel/trace"
)

func TestNewHandlerContract(t *testing.T) {
	ctx := context.Background()
	exporter := tracetest.NewInMemoryExporter()
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithSyncer(exporter),
	)
	defer func() { _ = tp.Shutdown(ctx) }()

	// 1. NewHandler wraps an http.Handler with OpenTelemetry server span instrumentation.
	var capturedSpanCtx trace.SpanContext
	innerHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		span := trace.SpanFromContext(r.Context())
		capturedSpanCtx = span.SpanContext()
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte("response-body"))
	})

	instrumented := sample.WrapHandler(innerHandler, "users-endpoint", sample.ServerOptions{
		TracerProvider: tp,
	})

	req1 := httptest.NewRequest(http.MethodGet, "http://localhost:8080/users", nil)
	rec1 := httptest.NewRecorder()
	instrumented.ServeHTTP(rec1, req1)

	if rec1.Code != http.StatusOK {
		t.Fatalf("expected status 200, got %d", rec1.Code)
	}
	spans := exporter.GetSpans()
	if len(spans) != 1 {
		t.Fatalf("expected 1 span, got %d", len(spans))
	}
	if spans[0].SpanKind != trace.SpanKindServer {
		t.Fatalf("expected server span kind, got %v", spans[0].SpanKind)
	}
	if spans[0].Name != "GET" {
		t.Fatalf("expected default span name 'GET', got %q", spans[0].Name)
	}

	// 2. NewHandler injects a valid SpanContext into the request context accessible by inner handlers.
	if !capturedSpanCtx.IsValid() {
		t.Fatal("captured span context in inner handler is invalid")
	}
	if capturedSpanCtx.TraceID() != spans[0].SpanContext.TraceID() {
		t.Fatalf("trace ID mismatch: inner context %s, recorded span %s",
			capturedSpanCtx.TraceID(), spans[0].SpanContext.TraceID())
	}

	// 3. NewHandler formats span name dynamically using WithSpanNameFormatter.
	exporter.Reset()
	customFormatter := func(operation string, r *http.Request) string {
		return r.Method + " " + r.URL.Path
	}
	formattedHandler := sample.WrapHandler(innerHandler, "fallback-name", sample.ServerOptions{
		TracerProvider: tp,
		NameFormatter:  customFormatter,
	})

	req2 := httptest.NewRequest(http.MethodPost, "http://localhost:8080/items/create", strings.NewReader("data"))
	rec2 := httptest.NewRecorder()
	formattedHandler.ServeHTTP(rec2, req2)

	spans = exporter.GetSpans()
	if len(spans) != 1 {
		t.Fatalf("expected 1 span for formatted handler, got %d", len(spans))
	}
	if spans[0].Name != "POST /items/create" {
		t.Fatalf("expected span name 'POST /items/create', got %q", spans[0].Name)
	}

	// 4. NewHandler skips tracing for requests excluded by WithFilter.
	exporter.Reset()
	filter := func(r *http.Request) bool {
		return r.URL.Path != "/healthz"
	}
	filteredHandler := sample.WrapHandler(innerHandler, "filtered-op", sample.ServerOptions{
		TracerProvider: tp,
		Filter:         filter,
	})

	reqHealth := httptest.NewRequest(http.MethodGet, "http://localhost:8080/healthz", nil)
	recHealth := httptest.NewRecorder()
	filteredHandler.ServeHTTP(recHealth, reqHealth)

	if len(exporter.GetSpans()) != 0 {
		t.Fatalf("expected 0 spans for filtered path /healthz, got %d", len(exporter.GetSpans()))
	}

	reqActive := httptest.NewRequest(http.MethodGet, "http://localhost:8080/active", nil)
	recActive := httptest.NewRecorder()
	filteredHandler.ServeHTTP(recActive, reqActive)

	if len(exporter.GetSpans()) != 1 {
		t.Fatalf("expected 1 span for active request, got %d", len(exporter.GetSpans()))
	}

	// 5. NewHandler records response status code on the completed server span.
	exporter.Reset()
	errorHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusNotFound)
		_, _ = w.Write([]byte("not found"))
	})
	errorInstrumented := sample.WrapHandler(errorHandler, "error-op", sample.ServerOptions{
		TracerProvider: tp,
	})

	req404 := httptest.NewRequest(http.MethodGet, "http://localhost:8080/missing", nil)
	rec404 := httptest.NewRecorder()
	errorInstrumented.ServeHTTP(rec404, req404)

	if rec404.Code != http.StatusNotFound {
		t.Fatalf("expected status 404, got %d", rec404.Code)
	}
	spans = exporter.GetSpans()
	if len(spans) != 1 {
		t.Fatalf("expected 1 span for 404 response, got %d", len(spans))
	}

	// 6. Verify HelloHandler helper
	helloHandler := sample.HelloHandler()
	helloInstrumented := sample.WrapHandler(helloHandler, "hello-op", sample.ServerOptions{
		TracerProvider: tp,
	})
	reqHello := httptest.NewRequest(http.MethodGet, "http://localhost:8080/hello", nil)
	recHello := httptest.NewRecorder()
	helloInstrumented.ServeHTTP(recHello, reqHello)

	body, _ := io.ReadAll(recHello.Body)
	if !strings.Contains(string(body), "hello from instrumented handler") {
		t.Fatalf("unexpected body: %s", string(body))
	}
	if recHello.Header().Get("X-Trace-ID") == "" {
		t.Fatal("expected X-Trace-ID header to be populated")
	}
}

{
  "schemaVersion": 1,
  "goal": "verify go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler in pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp@v0.70.0"
  ],
  "symbols": [
    "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewHandler"
  ]
}