tracing: add trace_id var (http.vars.trace_id placeholder) (#6308)

matthewpi · web-flow · commit 0b5720faa548 · 2024-05-08T16:40:40.000-06:00
diff --git a/modules/caddyhttp/tracing/tracer.go b/modules/caddyhttp/tracing/tracer.go
@@ -87,8 +87,12 @@ func (ot *openTelemetryWrapper) serveHTTP(w http.ResponseWriter, r *http.Request
 	ot.propagators.Inject(ctx, propagation.HeaderCarrier(r.Header))
 	spanCtx := trace.SpanContextFromContext(ctx)
 	if spanCtx.IsValid() {
+		traceID := spanCtx.TraceID().String()
+		// Add a trace_id placeholder, accessible via `{http.vars.trace_id}`.
+		caddyhttp.SetVar(ctx, "trace_id", traceID)
+		// Add the trace id to the log fields for the request.
 		if extra, ok := ctx.Value(caddyhttp.ExtraLogFieldsCtxKey).(*caddyhttp.ExtraLogFields); ok {
-			extra.Add(zap.String("traceID", spanCtx.TraceID().String()))
+			extra.Add(zap.String("traceID", traceID))
 		}
 	}
 	next := ctx.Value(nextCallCtxKey).(*nextCall)

Original file line number	Diff line number	Diff line change
`@@ -87,8 +87,12 @@ func (ot openTelemetryWrapper) serveHTTP(w http.ResponseWriter, r http.Request`
`87`	`87`	`ot.propagators.Inject(ctx, propagation.HeaderCarrier(r.Header))`
`88`	`88`	`spanCtx := trace.SpanContextFromContext(ctx)`
`89`	`89`	`if spanCtx.IsValid() {`
	`90`	`+ traceID := spanCtx.TraceID().String()`
	`91`	+ // Add a trace_id placeholder, accessible via `{http.vars.trace_id}`.
	`92`	`+ caddyhttp.SetVar(ctx, "trace_id", traceID)`
	`93`	`+ // Add the trace id to the log fields for the request.`
`90`	`94`	`if extra, ok := ctx.Value(caddyhttp.ExtraLogFieldsCtxKey).(*caddyhttp.ExtraLogFields); ok {`
`91`		`- extra.Add(zap.String("traceID", spanCtx.TraceID().String()))`
	`95`	`+ extra.Add(zap.String("traceID", traceID))`
`92`	`96`	`}`
`93`	`97`	`}`
`94`	`98`	`next := ctx.Value(nextCallCtxKey).(*nextCall)`