[PATCH] Proxy: altered limit_rate to support variables
J Carter
jordanc.carter at outlook.com
Thu Dec 28 10:48:20 UTC 2023
Hello,
Thanks for the review and feedback.
On Tue, 26 Dec 2023 19:07:37 +0400
Sergey Kandaurov <pluknet at nginx.com> wrote:
> > On 26 Nov 2023, at 03:37, J Carter <jordanc.carter at outlook.com> wrote:
> >
> > # HG changeset patch
> > # User J Carter <jordan.carter at outlook.com>
> > # Date 1700949429 0
> > # Sat Nov 25 21:57:09 2023 +0000
> > # Node ID 98306e705015758eab0a05103d90e6bdb1da2819
> > # Parent f366007dd23a6ce8e8427c1b3042781b618a2ade
> > Proxy: altered limit_rate to support variables
>
> Since it changes the upstream interface, I'd rather say:
>
> Upstream: variables support in proxy_limit_rate and friends.
>
Yep, makes sense.
>
> The change looks good to me, also it compliments variables support
> in the stream proxy module's directives.
> Any particular use-cases you'd like to share for this functionality?
>
There are several, many are quite 'involved'.
A variable proxy_limit_rate (driven by external means), combined with
max_conns set on upstream servers gives a reasonable method of
dynamically capping upstream bandwidth utilization.
One scenario in which this has come up is when nginx is used a caching
server, as often upstream servers cannot support 100% of the 'real'
traffic load.
When the cache is cleared or many items expire concurrently, requests
reaching the upstream can spike and it is necessary to adjust (down)
proxy_limit_rate in a semi continuous fashion to prevent overloading
upstreams as they serve responses.
A novel way of showing this using only core modules is:
upstream backend {
server 127.0.0.1:8080 max_conns=100;
...
}
... <proxy-cache-path, and related directives>
server {
listen 80;
location / {
...
proxy_pass http://backend;
proxy_hide_header rate;
proxy_limit_rate $upstream_http_rate;
}
}
...
server {
listen 8080;
location / {
#serve a file
...
add_header rate $my_rate;
}
}
Of course, this is most useful where 'backend' isn't nginx, and doesn't
have it's own client side bandwidth limiting (ie. limit_rate,
limit_rate_after, limit_conn) - I've just used it here for this example for
convenience.
> >
> > diff -r f366007dd23a -r 98306e705015 src/http/modules/ngx_http_fastcgi_module.c
> > --- a/src/http/modules/ngx_http_fastcgi_module.c Tue Nov 14 15:26:02 2023 +0400
> > +++ b/src/http/modules/ngx_http_fastcgi_module.c Sat Nov 25 21:57:09 2023 +0000
> > @@ -375,7 +375,7 @@
> >
> > { ngx_string("fastcgi_limit_rate"),
> > NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
> > - ngx_conf_set_size_slot,
> > + ngx_http_set_complex_value_size_slot,
> > NGX_HTTP_LOC_CONF_OFFSET,
> > offsetof(ngx_http_fastcgi_loc_conf_t, upstream.limit_rate),
> > NULL },
> > @@ -2898,7 +2898,7 @@
> >
> > conf->upstream.send_lowat = NGX_CONF_UNSET_SIZE;
> > conf->upstream.buffer_size = NGX_CONF_UNSET_SIZE;
> > - conf->upstream.limit_rate = NGX_CONF_UNSET_SIZE;
> > + conf->upstream.limit_rate = NGX_CONF_UNSET_PTR;
> >
> > conf->upstream.busy_buffers_size_conf = NGX_CONF_UNSET_SIZE;
> > conf->upstream.max_temp_file_size_conf = NGX_CONF_UNSET_SIZE;
> > @@ -3015,8 +3015,8 @@
> > prev->upstream.buffer_size,
> > (size_t) ngx_pagesize);
> >
> > - ngx_conf_merge_size_value(conf->upstream.limit_rate,
> > - prev->upstream.limit_rate, 0);
> > + ngx_conf_merge_ptr_value(conf->upstream.limit_rate,
> > + prev->upstream.limit_rate, NULL);
> >
> >
> > ngx_conf_merge_bufs_value(conf->upstream.bufs, prev->upstream.bufs,
> > diff -r f366007dd23a -r 98306e705015 src/http/modules/ngx_http_proxy_module.c
> > --- a/src/http/modules/ngx_http_proxy_module.c Tue Nov 14 15:26:02 2023 +0400
> > +++ b/src/http/modules/ngx_http_proxy_module.c Sat Nov 25 21:57:09 2023 +0000
> > @@ -494,7 +494,7 @@
> >
> > { ngx_string("proxy_limit_rate"),
> > NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
> > - ngx_conf_set_size_slot,
> > + ngx_http_set_complex_value_size_slot,
> > NGX_HTTP_LOC_CONF_OFFSET,
> > offsetof(ngx_http_proxy_loc_conf_t, upstream.limit_rate),
> > NULL },
> > @@ -3371,7 +3371,7 @@
> >
> > conf->upstream.send_lowat = NGX_CONF_UNSET_SIZE;
> > conf->upstream.buffer_size = NGX_CONF_UNSET_SIZE;
> > - conf->upstream.limit_rate = NGX_CONF_UNSET_SIZE;
> > + conf->upstream.limit_rate = NGX_CONF_UNSET_PTR;
> >
> > conf->upstream.busy_buffers_size_conf = NGX_CONF_UNSET_SIZE;
> > conf->upstream.max_temp_file_size_conf = NGX_CONF_UNSET_SIZE;
> > @@ -3515,8 +3515,8 @@
> > prev->upstream.buffer_size,
> > (size_t) ngx_pagesize);
> >
> > - ngx_conf_merge_size_value(conf->upstream.limit_rate,
> > - prev->upstream.limit_rate, 0);
> > + ngx_conf_merge_ptr_value(conf->upstream.limit_rate,
> > + prev->upstream.limit_rate, NULL);
> >
> > ngx_conf_merge_bufs_value(conf->upstream.bufs, prev->upstream.bufs,
> > 8, ngx_pagesize);
> > diff -r f366007dd23a -r 98306e705015 src/http/modules/ngx_http_scgi_module.c
> > --- a/src/http/modules/ngx_http_scgi_module.c Tue Nov 14 15:26:02 2023 +0400
> > +++ b/src/http/modules/ngx_http_scgi_module.c Sat Nov 25 21:57:09 2023 +0000
> > @@ -223,7 +223,7 @@
> >
> > { ngx_string("scgi_limit_rate"),
> > NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
> > - ngx_conf_set_size_slot,
> > + ngx_http_set_complex_value_size_slot,
> > NGX_HTTP_LOC_CONF_OFFSET,
> > offsetof(ngx_http_scgi_loc_conf_t, upstream.limit_rate),
> > NULL },
> > @@ -1301,7 +1301,7 @@
> >
> > conf->upstream.send_lowat = NGX_CONF_UNSET_SIZE;
> > conf->upstream.buffer_size = NGX_CONF_UNSET_SIZE;
> > - conf->upstream.limit_rate = NGX_CONF_UNSET_SIZE;
> > + conf->upstream.limit_rate = NGX_CONF_UNSET_PTR;
> >
> > conf->upstream.busy_buffers_size_conf = NGX_CONF_UNSET_SIZE;
> > conf->upstream.max_temp_file_size_conf = NGX_CONF_UNSET_SIZE;
> > @@ -1413,8 +1413,8 @@
> > prev->upstream.buffer_size,
> > (size_t) ngx_pagesize);
> >
> > - ngx_conf_merge_size_value(conf->upstream.limit_rate,
> > - prev->upstream.limit_rate, 0);
> > + ngx_conf_merge_ptr_value(conf->upstream.limit_rate,
> > + prev->upstream.limit_rate, NULL);
> >
> >
> > ngx_conf_merge_bufs_value(conf->upstream.bufs, prev->upstream.bufs,
> > diff -r f366007dd23a -r 98306e705015 src/http/modules/ngx_http_uwsgi_module.c
> > --- a/src/http/modules/ngx_http_uwsgi_module.c Tue Nov 14 15:26:02 2023 +0400
> > +++ b/src/http/modules/ngx_http_uwsgi_module.c Sat Nov 25 21:57:09 2023 +0000
> > @@ -289,7 +289,7 @@
> >
> > { ngx_string("uwsgi_limit_rate"),
> > NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
> > - ngx_conf_set_size_slot,
> > + ngx_http_set_complex_value_size_slot,
> > NGX_HTTP_LOC_CONF_OFFSET,
> > offsetof(ngx_http_uwsgi_loc_conf_t, upstream.limit_rate),
> > NULL },
> > @@ -1532,7 +1532,7 @@
> >
> > conf->upstream.send_lowat = NGX_CONF_UNSET_SIZE;
> > conf->upstream.buffer_size = NGX_CONF_UNSET_SIZE;
> > - conf->upstream.limit_rate = NGX_CONF_UNSET_SIZE;
> > + conf->upstream.limit_rate = NGX_CONF_UNSET_PTR;
> >
> > conf->upstream.busy_buffers_size_conf = NGX_CONF_UNSET_SIZE;
> > conf->upstream.max_temp_file_size_conf = NGX_CONF_UNSET_SIZE;
> > @@ -1656,8 +1656,8 @@
> > prev->upstream.buffer_size,
> > (size_t) ngx_pagesize);
> >
> > - ngx_conf_merge_size_value(conf->upstream.limit_rate,
> > - prev->upstream.limit_rate, 0);
> > + ngx_conf_merge_ptr_value(conf->upstream.limit_rate,
> > + prev->upstream.limit_rate, NULL);
> >
> >
> > ngx_conf_merge_bufs_value(conf->upstream.bufs, prev->upstream.bufs,
> > diff -r f366007dd23a -r 98306e705015 src/http/ngx_http_upstream.c
> > --- a/src/http/ngx_http_upstream.c Tue Nov 14 15:26:02 2023 +0400
> > +++ b/src/http/ngx_http_upstream.c Sat Nov 25 21:57:09 2023 +0000
> > @@ -3236,7 +3236,7 @@
> > p->downstream = c;
> > p->pool = r->pool;
> > p->log = c->log;
> > - p->limit_rate = u->conf->limit_rate;
> > + p->limit_rate = ngx_http_complex_value_size(r, u->conf->limit_rate, 0);
> > p->start_sec = ngx_time();
> >
> > p->cacheable = u->cacheable || u->store;
> > diff -r f366007dd23a -r 98306e705015 src/http/ngx_http_upstream.h
> > --- a/src/http/ngx_http_upstream.h Tue Nov 14 15:26:02 2023 +0400
> > +++ b/src/http/ngx_http_upstream.h Sat Nov 25 21:57:09 2023 +0000
> > @@ -156,7 +156,7 @@
> >
> > size_t send_lowat;
> > size_t buffer_size;
> > - size_t limit_rate;
> > + ngx_http_complex_value_t *limit_rate;
> >
> > size_t busy_buffers_size;
> > size_t max_temp_file_size;
>
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