I noticed that currently mod_proxy_http2 cannot serve responses larger
than 32 KiB for incoming requests over HTTP/1.1. Below is a simple
config that can be used to reproduce the problem:
LoadModule http2_module modules/mod_http2.so
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
LoadModule proxy_http2_module modules/mod_proxy_http2.so
ProxyPass "/" "h2c://nghttp2.org/"
Issuing an HTTP/1.1 request to a file that exceeds 32 KiB is going to
stall and eventually fail:
curl --http1.1 http://localhost/stylesheets/screen.css
...
curl: (18) transfer closed with 6016 bytes remaining to read
The reason is that in this particular case mod_proxy_http2 doesn't update
the HTTP/2 flow control windows. Once the amount of the received data
hits a hardcoded threshold of 32 KiB, no data can be received without
a WINDOW_UPDATE, and since it doesn't happen, the request eventually
times out.
Please see the push_request_somewhere() function in mod_proxy_http2.c:441:
if (!ctx->engine) {
/* No engine was available or has been initialized, handle this
* request just by ourself. */
ctx->engine_id = apr_psprintf(ctx->pool, "eng-proxy-%ld", c->id);
ctx->engine_type = engine_type;
ctx->engine_pool = ctx->pool;
ctx->req_buffer_size = (32*1024);
ctx->standalone = 1;
...
Currently, mod_proxy_http2 can either handle the request to a backend
by itself or push the handling of the request to the mod_http2's request
engine. In the latter case, the HTTP/2 flow control windows are updated
per the h2_req_engine_out_consumed() function calls. But if mod_proxy_http2
processes the request by itself, they are not. This is exactly what happens
in the described case with the HTTP/1.1 request.
I attached the patch with a fix for this issue. The idea behind the patch
is that we keep track of how a particular request is handled and call the
nghttp2_session_consume() function if that's required.
Regards,
Evgeny Kotkov
Index: modules/http2/h2_proxy_session.c
===================================================================
--- modules/http2/h2_proxy_session.c (revision 1747688)
+++ modules/http2/h2_proxy_session.c (working copy)
@@ -36,6 +36,7 @@ typedef struct h2_proxy_stream {
const char *url;
request_rec *r;
h2_request *req;
+ int standalone;
h2_stream_state_t state;
unsigned int suspended : 1;
@@ -370,6 +371,12 @@ static int on_data_chunk_recv(nghttp2_session *ngh
stream_id, NGHTTP2_STREAM_CLOSED);
return NGHTTP2_ERR_STREAM_CLOSING;
}
+ if (stream->standalone) {
+ nghttp2_session_consume(ngh2, stream_id, len);
+ ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, stream->r,
+ "h2_proxy_session(%s): stream %d, win_update %d bytes",
+ session->id, stream_id, (int)len);
+ }
return 0;
}
@@ -576,7 +583,8 @@ static apr_status_t session_start(h2_proxy_session
}
static apr_status_t open_stream(h2_proxy_session *session, const char *url,
- request_rec *r, h2_proxy_stream **pstream)
+ request_rec *r, int standalone,
+ h2_proxy_stream **pstream)
{
h2_proxy_stream *stream;
apr_uri_t puri;
@@ -588,6 +596,7 @@ static apr_status_t open_stream(h2_proxy_session *
stream->pool = r->pool;
stream->url = url;
stream->r = r;
+ stream->standalone = standalone;
stream->session = session;
stream->state = H2_STREAM_ST_IDLE;
@@ -761,12 +770,13 @@ static apr_status_t h2_proxy_session_read(h2_proxy
}
apr_status_t h2_proxy_session_submit(h2_proxy_session *session,
- const char *url, request_rec *r)
+ const char *url, request_rec *r,
+ int standalone)
{
h2_proxy_stream *stream;
apr_status_t status;
- status = open_stream(session, url, r, &stream);
+ status = open_stream(session, url, r, standalone, &stream);
if (status == APR_SUCCESS) {
ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(03381)
"process stream(%d): %s %s%s, original: %s",
Index: modules/http2/h2_proxy_session.h
===================================================================
--- modules/http2/h2_proxy_session.h (revision 1747688)
+++ modules/http2/h2_proxy_session.h (working copy)
@@ -89,7 +89,7 @@ h2_proxy_session *h2_proxy_session_setup(const cha
h2_proxy_request_done *done);
apr_status_t h2_proxy_session_submit(h2_proxy_session *s, const char *url,
- request_rec *r);
+ request_rec *r, int standalone);
/**
* Perform a step in processing the proxy session. Will return aftert
Index: modules/http2/mod_proxy_http2.c
===================================================================
--- modules/http2/mod_proxy_http2.c (revision 1747688)
+++ modules/http2/mod_proxy_http2.c (working copy)
@@ -258,7 +258,7 @@ static apr_status_t add_request(h2_proxy_session *
url = apr_table_get(r->notes, H2_PROXY_REQ_URL_NOTE);
apr_table_setn(r->notes, "proxy-source-port", apr_psprintf(r->pool, "%hu",
ctx->p_conn->connection->local_addr->port));
- status = h2_proxy_session_submit(session, url, r);
+ status = h2_proxy_session_submit(session, url, r, ctx->standalone);
if (status != APR_SUCCESS) {
ap_log_cerror(APLOG_MARK, APLOG_ERR, status, r->connection,
APLOGNO(03351)
"pass request body failed to %pI (%s) from %s (%s)",
