| 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 | } |
| 118 |