reverseproxy: Fix retries for requests with bodies (#7360)

* capture the buffered body once, then reset clonedReq.Body before each retry * no copy * keep receiver name * set the buf to nil after extraction and only return it to pool if not nil --------- Co-authored-by: WeidiDeng <weidi_deng@icloud.com>

Petr committed Nov 24, 2025 at 23:03 UTC 67a9e0657e60df8c78510065e8977d86ee17d01c

1 file changed +22 -3

modules/caddyhttp/reverseproxy/reverseproxy.go

+22 -3

@@ -437,6 +437,20 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht

437 reqHost := clonedReq.Host

438 reqHeader := clonedReq.Header

439

440 + // If the cloned request body was fully buffered, keep a reference to its

441 + // buffer so we can reuse it across retries and return it to the pool

442 + // once we’re done.

443 + var bufferedReqBody *bytes.Buffer

444 + if reqBodyBuf, ok := clonedReq.Body.(bodyReadCloser); ok && reqBodyBuf.body == nil && reqBodyBuf.buf != nil {

445 + bufferedReqBody = reqBodyBuf.buf

446 + reqBodyBuf.buf = nil

447 +

448 + defer func() {

449 + bufferedReqBody.Reset()

450 + bufPool.Put(bufferedReqBody)

451 + }()

452 + }

453 +

454 start := time.Now()

455 defer func() {

456 // total proxying duration, including time spent on LB and retries

@@ -455,8 +469,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht

469 // and reusable, so if a backend partially or fully reads the body but then

470 // produces an error, the request can be repeated to the next backend with

471 // the full body (retries should only happen for idempotent requests) (see #6259)

458 - if reqBodyBuf, ok := r.Body.(bodyReadCloser); ok && reqBodyBuf.body == nil {

459 - r.Body = io.NopCloser(bytes.NewReader(reqBodyBuf.buf.Bytes()))

472 + if bufferedReqBody != nil {

473 + clonedReq.Body = io.NopCloser(bytes.NewReader(bufferedReqBody.Bytes()))

474 }

475

476 var done bool

@@ -1538,7 +1552,12 @@ type bodyReadCloser struct {

1552 }

1553

1554 func (brc bodyReadCloser) Close() error {

1541 - bufPool.Put(brc.buf)

1555 + // Inside this package this will be set to nil for fully-buffered

1556 + // requests due to the possibility of retrial.

1557 + if brc.buf != nil {

1558 + bufPool.Put(brc.buf)

1559 + }

1560 + // For fully-buffered bodies, body is nil, so Close is a no-op.

1561 if brc.body != nil {

1562 return brc.body.Close()

1563 }