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Fast and extensible multi-platform HTTP/1-2-3 web server with automatic HTTPS

Mirrored from https://github.com/Slazee/caddy.git

Synced Nov 11, 07:15 UTC

caddyhttp: allocate the request UUID lazily instead of on every request (#7936)

addHTTPVarsToReplacer ran SetVar(ctx, "uuid", new(requestID)) for every request during replacer setup, allocating a *requestID unconditionally even though it is only ever read by the {http.request.uuid} placeholder. The UUID value itself was already generated lazily (requestID.String caches on first call), but the container was not. Allocate the *requestID on first access instead: the uuid placeholder now creates and stores it in the request's vars table when absent, so repeated references within a request still share one instance (and thus one UUID), while requests that never reference the UUID pay nothing. Add a benchmark for the per-request replacer setup and a regression test for the uuid placeholder, which previously had no coverage. Benchmark (BenchmarkAddHTTPVarsToReplacer, linux/arm64, count=6), common path where the UUID is never referenced: before: ~700 ns/op 352 B/op 9 allocs/op after: ~690 ns/op 336 B/op 8 allocs/op One 16-byte allocation removed per request; a GC-pressure win rather than a latency one.

Julien Voisin committed Aug 11, 2026 at 13:21 UTC 63f4e387c33e42864ad80ed704595299c3f8128b

2 files changed +47 -3

modules/caddyhttp/replacer.go

+8 -3

@@ -57,7 +57,6 @@ func NewTestReplacer(req *http.Request) *caddy.Replacer {

58 func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.ResponseWriter) {

59 SetVar(req.Context(), "start_time", time.Now())

60 - SetVar(req.Context(), "uuid", new(requestID))

61 httpVars := func(key string) (any, bool) {

62 if req != nil {

@@ -213,8 +212,14 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo

212 return time.Since(start).Seconds() * 1e3, true // multiply seconds to preserve decimal (see #4666)

213

214 case "http.request.uuid":

216 - // fetch the UUID for this request

217 - id := GetVar(req.Context(), "uuid").(*requestID)

215 + // fetch the UUID for this request, generating and caching it

216 + // on first access so requests that never reference the UUID

217 + // don't pay for the allocation

218 + id, ok := GetVar(req.Context(), "uuid").(*requestID)

219 + if !ok {

220 + id = new(requestID)

221 + SetVar(req.Context(), "uuid", id)

222 + }

223

224 // set it to this request's access log

225 extra := req.Context().Value(ExtraLogFieldsCtxKey).(*ExtraLogFields)

modules/caddyhttp/replacer_test.go

+39

@@ -296,3 +296,42 @@ func TestHTTPProtoNameNormalization(t *testing.T) {

296 }

297 }

298 }

299 +

300 +// BenchmarkAddHTTPVarsToReplacer measures the per-request replacer setup, which

301 +// is the common path where the request UUID is never referenced.

302 +func BenchmarkAddHTTPVarsToReplacer(b *testing.B) {

303 + req := httptest.NewRequest(http.MethodGet, "http://example.com/foo?a=b", nil)

304 + req.Header.Set("User-Agent", "test-agent")

305 + ctx := context.WithValue(req.Context(), VarsCtxKey, make(map[string]any))

306 + ctx = context.WithValue(ctx, ExtraLogFieldsCtxKey, new(ExtraLogFields))

307 + req = req.WithContext(ctx)

308 +

309 + b.ReportAllocs()

310 + for b.Loop() {

311 + repl := caddy.NewReplacer()

312 + addHTTPVarsToReplacer(repl, req, nil)

313 + }

314 +}

315 +

316 +// TestHTTPVarReplacementUUID verifies the lazily-allocated request UUID is

317 +// generated on first access and stays stable across references.

318 +func TestHTTPVarReplacementUUID(t *testing.T) {

319 + req := httptest.NewRequest(http.MethodGet, "http://example.com/", nil)

320 + repl := caddy.NewReplacer()

321 + ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)

322 + ctx = context.WithValue(ctx, VarsCtxKey, make(map[string]any))

323 + ctx = context.WithValue(ctx, ExtraLogFieldsCtxKey, new(ExtraLogFields))

324 + req = req.WithContext(ctx)

325 + addHTTPVarsToReplacer(repl, req, nil)

326 +

327 + first, ok := repl.GetString("http.request.uuid")

328 + if !ok || first == "" {

329 + t.Fatalf("expected a non-empty uuid, got %q (ok=%t)", first, ok)

330 + }

331 +

332 + second, _ := repl.GetString("http.request.uuid")

333 + if first != second {

334 + t.Errorf("expected stable uuid across references: %q != %q", first, second)

335 + }

336 +}

337 +