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| 1 | +// SPDX-License-Identifier: AGPL-3.0-or-later |
| 2 | + |
| 3 | +// Package tracing wires the OpenTelemetry SDK and exposes a small |
| 4 | +// HTTP-middleware helper. When tracing is disabled, all helpers are no-ops |
| 5 | +// so callers don't need to branch. |
| 6 | +package tracing |
| 7 | + |
| 8 | +import ( |
| 9 | + "context" |
| 10 | + "errors" |
| 11 | + "fmt" |
| 12 | + "net/http" |
| 13 | + "net/url" |
| 14 | + "time" |
| 15 | + |
| 16 | + "go.opentelemetry.io/otel" |
| 17 | + "go.opentelemetry.io/otel/attribute" |
| 18 | + "go.opentelemetry.io/otel/exporters/otlp/otlptrace" |
| 19 | + "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp" |
| 20 | + "go.opentelemetry.io/otel/propagation" |
| 21 | + "go.opentelemetry.io/otel/sdk/resource" |
| 22 | + sdktrace "go.opentelemetry.io/otel/sdk/trace" |
| 23 | + semconv "go.opentelemetry.io/otel/semconv/v1.27.0" |
| 24 | + "go.opentelemetry.io/otel/trace" |
| 25 | +) |
| 26 | + |
| 27 | +// Config controls the SDK setup. |
| 28 | +type Config struct { |
| 29 | + Enabled bool |
| 30 | + Endpoint string // OTLP HTTP endpoint, e.g. "http://otel-collector:4318" |
| 31 | + SampleRate float64 // 0..1 |
| 32 | + ServiceName string |
| 33 | +} |
| 34 | + |
| 35 | +// Init constructs the tracer provider per cfg and installs it as the |
| 36 | +// global OTel provider. Returns a shutdown function the caller invokes on |
| 37 | +// exit. When cfg.Enabled is false, returns a no-op shutdown. |
| 38 | +func Init(ctx context.Context, cfg Config) (func(context.Context) error, error) { |
| 39 | + if !cfg.Enabled { |
| 40 | + return func(context.Context) error { return nil }, nil |
| 41 | + } |
| 42 | + if cfg.Endpoint == "" { |
| 43 | + return nil, errors.New("tracing: endpoint required when enabled") |
| 44 | + } |
| 45 | + |
| 46 | + u, err := url.Parse(cfg.Endpoint) |
| 47 | + if err != nil { |
| 48 | + return nil, fmt.Errorf("tracing: parse endpoint: %w", err) |
| 49 | + } |
| 50 | + opts := []otlptracehttp.Option{ |
| 51 | + otlptracehttp.WithEndpoint(u.Host), |
| 52 | + otlptracehttp.WithURLPath(u.Path), |
| 53 | + } |
| 54 | + if u.Scheme != "https" { |
| 55 | + opts = append(opts, otlptracehttp.WithInsecure()) |
| 56 | + } |
| 57 | + |
| 58 | + exporter, err := otlptrace.New(ctx, otlptracehttp.NewClient(opts...)) |
| 59 | + if err != nil { |
| 60 | + return nil, fmt.Errorf("tracing: exporter: %w", err) |
| 61 | + } |
| 62 | + |
| 63 | + res, err := resource.Merge( |
| 64 | + resource.Default(), |
| 65 | + resource.NewWithAttributes( |
| 66 | + semconv.SchemaURL, |
| 67 | + semconv.ServiceName(cfg.ServiceName), |
| 68 | + ), |
| 69 | + ) |
| 70 | + if err != nil { |
| 71 | + return nil, fmt.Errorf("tracing: resource: %w", err) |
| 72 | + } |
| 73 | + |
| 74 | + provider := sdktrace.NewTracerProvider( |
| 75 | + sdktrace.WithBatcher( |
| 76 | + exporter, |
| 77 | + sdktrace.WithBatchTimeout(5*time.Second), |
| 78 | + ), |
| 79 | + sdktrace.WithSampler(sdktrace.ParentBased(sdktrace.TraceIDRatioBased(cfg.SampleRate))), |
| 80 | + sdktrace.WithResource(res), |
| 81 | + ) |
| 82 | + otel.SetTracerProvider(provider) |
| 83 | + otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator( |
| 84 | + propagation.TraceContext{}, |
| 85 | + propagation.Baggage{}, |
| 86 | + )) |
| 87 | + |
| 88 | + return func(ctx context.Context) error { |
| 89 | + shutdownCtx, cancel := context.WithTimeout(ctx, 5*time.Second) |
| 90 | + defer cancel() |
| 91 | + return provider.Shutdown(shutdownCtx) |
| 92 | + }, nil |
| 93 | +} |
| 94 | + |
| 95 | +// Tracer returns a named tracer from the global provider. Safe to call when |
| 96 | +// tracing is disabled (returns a no-op tracer). |
| 97 | +func Tracer(name string) trace.Tracer { |
| 98 | + return otel.Tracer(name) |
| 99 | +} |
| 100 | + |
| 101 | +// Middleware returns HTTP middleware that emits one span per request, |
| 102 | +// linking it to the request_id when present. |
| 103 | +func Middleware(next http.Handler) http.Handler { |
| 104 | + tracer := Tracer("shithub.web") |
| 105 | + return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { |
| 106 | + ctx, span := tracer.Start( |
| 107 | + r.Context(), r.Method+" "+r.URL.Path, |
| 108 | + trace.WithSpanKind(trace.SpanKindServer), |
| 109 | + trace.WithAttributes( |
| 110 | + attribute.String("http.method", r.Method), |
| 111 | + attribute.String("http.path", r.URL.Path), |
| 112 | + ), |
| 113 | + ) |
| 114 | + defer span.End() |
| 115 | + next.ServeHTTP(w, r.WithContext(ctx)) |
| 116 | + }) |
| 117 | +} |