reverseproxy: Ignore context cancel in stream mode (#4952)

Matt Holt committed Aug 12, 2022 at 13:15 UTC f5dce84a7028d1b116db7fead27ff8b2506baf78

1 file changed +27

modules/caddyhttp/reverseproxy/reverseproxy.go

+27

@@ -109,6 +109,11 @@ type Handler struct {

109 // response is recognized as a streaming response, or if its

110 // content length is -1; for such responses, writes are flushed

111 // to the client immediately.

112 + //

113 + // Normally, a request will be canceled if the client disconnects

114 + // before the response is received from the backend. If explicitly

115 + // set to -1, client disconnection will be ignored and the request

116 + // will be completed to help facilitate low-latency streaming.

117 FlushInterval caddy.Duration `json:"flush_interval,omitempty"`

118

119 // A list of IP ranges (supports CIDR notation) from which

@@ -757,6 +762,15 @@ func (h *Handler) reverseProxy(rw http.ResponseWriter, req *http.Request, origRe

762 req = req.WithContext(httptrace.WithClientTrace(req.Context(), trace))

763 }

764

765 + // if FlushInterval is explicitly configured to -1 (i.e. flush continuously to achieve

766 + // low-latency streaming), don't let the transport cancel the request if the client

767 + // disconnects: user probably wants us to finish sending the data to the upstream

768 + // regardless, and we should expect client disconnection in low-latency streaming

769 + // scenarios (see issue #4922)

770 + if h.FlushInterval == -1 {

771 + req = req.WithContext(ignoreClientGoneContext{req.Context(), h.ctx.Done()})

772 + }

773 +

774 // do the round-trip; emit debug log with values we know are

775 // safe, or if there is no error, emit fuller log entry

776 start := time.Now()

@@ -1374,6 +1388,19 @@ type handleResponseContext struct {

1388 isFinalized bool

1389 }

1390

1391 +// ignoreClientGoneContext is a special context.Context type

1392 +// intended for use when doing a RoundTrip where you don't

1393 +// want a client disconnection to cancel the request during

1394 +// the roundtrip. Set its done field to a Done() channel

1395 +// of a context that doesn't get canceled when the client

1396 +// disconnects, such as caddy.Context.Done() instead.

1397 +type ignoreClientGoneContext struct {

1398 + context.Context

1399 + done <-chan struct{}

1400 +}

1401 +

1402 +func (c ignoreClientGoneContext) Done() <-chan struct{} { return c.done }

1403 +

1404 // proxyHandleResponseContextCtxKey is the context key for the active proxy handler

1405 // so that handle_response routes can inherit some config options

1406 // from the proxy handler.