Changed keepalive_requests default to 1000 (ticket #2155).

It turns out no browsers implement HTTP/2 GOAWAY handling properly, and
large enough number of resources on a page results in failures to load
some resources.  In particular, Chrome seems to experience errors if
loading of all resources requires more than 1 connection (while it
is usually able to retry requests at least once, even with 2 connections
there are occasional failures for some reason), Safari if loading requires
more than 3 connections, and Firefox if loading requires more than 10
connections (can be configured with network.http.request.max-attempts,
defaults to 10).

It does not seem to be possible to resolve this on nginx side, even strict
limiting of maximum concurrency does not help, and loading issues seems to
be triggered by merely queueing of a request for a particular connection.
The only available mitigation seems to use higher keepalive_requests value.

The new default is 1000 and matches previously used default for
http2_max_requests.  It is expected to be enough for 99.98% of the pages
(https://httparchive.org/reports/state-of-the-web?start=latest#reqTotal)
even in Chrome.

diff --git a/src/http/modules/ngx_http_upstream_keepalive_module.c b/src/http/modules/ngx_http_upstream_keepalive_module.c
index bbd650b791bed65da99c58c0a371050005b221d6..1a4dfd77665129c2dea4d7fef4544c3bc1d84e75 100644 (file)
--- a/src/http/modules/ngx_http_upstream_keepalive_module.c
+++ b/src/http/modules/ngx_http_upstream_keepalive_module.c
@@ -159,7 +159,7 @@ ngx_http_upstream_init_keepalive(ngx_conf_t *cf,
 
     ngx_conf_init_msec_value(kcf->time, 3600000);
     ngx_conf_init_msec_value(kcf->timeout, 60000);
-    ngx_conf_init_uint_value(kcf->requests, 100);
+    ngx_conf_init_uint_value(kcf->requests, 1000);
 
     if (kcf->original_init_upstream(cf, us) != NGX_OK) {
         return NGX_ERROR;

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 9dda27a104c6e7954f9df7badd3c90f41650bb75..6664fa6c398c43e2f729f3a40ce1bc85a279ff8c 100644 (file)
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -3758,7 +3758,7 @@ ngx_http_core_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_sec_value(conf->keepalive_header,
                               prev->keepalive_header, 0);
     ngx_conf_merge_uint_value(conf->keepalive_requests,
-                              prev->keepalive_requests, 100);
+                              prev->keepalive_requests, 1000);
     ngx_conf_merge_uint_value(conf->lingering_close,
                               prev->lingering_close, NGX_HTTP_LINGERING_ON);
     ngx_conf_merge_msec_value(conf->lingering_time,