@@ -0,0 +1,117 @@ |
| | 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 | +} |