switch to ms resolution for rate limiting

[Jérôme Loyet]

Hello,

I'm using rate limiting within the stream module. While it works great
for long connections it does not work on request smaller than the rate
limite size for 1 second. I set up a 1gbps rate limit (limit_rate
125m) and request smaller than 125M or not limited. This is a normal
behavioir as the rate limiting is done with a second precision. This
patch change second precision to millisecond precision. From my first
tests (still on going) it seems to works better.

What guys do you think about this patch ?

Thanks
++ Jerome


# HG changeset patch
# User Jerome Loyet <jerome at loyet.net>
# Date 1669612614 -3600
#      Mon Nov 28 06:16:54 2022 +0100
# Node ID a474ad7ca3408d2b09cd7bfbc827c8df84e3bd0c
# Parent  0b360747c74e3fa7e439e0684a8cf1da2d14d8f6
switch to ms resolution for rate limiting

rate limiting use a second resolution which can be bypassed on
requests/response smaller than the configured rate for 1 second.

This patch switches to millisecond resolution to ensure
better precision of the rate limiting.

diff -r 0b360747c74e -r a474ad7ca340 src/event/ngx_event_pipe.c
--- a/src/event/ngx_event_pipe.c    Thu Nov 24 23:08:30 2022 +0400
+++ b/src/event/ngx_event_pipe.c    Mon Nov 28 06:16:54 2022 +0100
@@ -203,8 +203,8 @@
                     break;
                 }

-                limit = (off_t) p->limit_rate * (ngx_time() - p->start_sec + 1)
-                        - p->read_length;
+                limit = (off_t) p->limit_rate * (ngx_current_msec -
p->start_msec + 1)
+                        / 1000 - p->read_length;

                 if (limit <= 0) {
                     p->upstream->read->delayed = 1;
diff -r 0b360747c74e -r a474ad7ca340 src/event/ngx_event_pipe.h
--- a/src/event/ngx_event_pipe.h    Thu Nov 24 23:08:30 2022 +0400
+++ b/src/event/ngx_event_pipe.h    Mon Nov 28 06:16:54 2022 +0100
@@ -91,7 +91,7 @@
     ngx_buf_t         *buf_to_file;

     size_t             limit_rate;
-    time_t             start_sec;
+    ngx_msec_t         start_msec;

     ngx_temp_file_t   *temp_file;

diff -r 0b360747c74e -r a474ad7ca340 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c    Thu Nov 24 23:08:30 2022 +0400
+++ b/src/http/ngx_http_upstream.c    Mon Nov 28 06:16:54 2022 +0100
@@ -3217,7 +3217,7 @@
     p->pool = r->pool;
     p->log = c->log;
     p->limit_rate = u->conf->limit_rate;
-    p->start_sec = ngx_time();
+    p->start_msec = ngx_current_msec;

     p->cacheable = u->cacheable || u->store;

diff -r 0b360747c74e -r a474ad7ca340 src/stream/ngx_stream_proxy_module.c
--- a/src/stream/ngx_stream_proxy_module.c    Thu Nov 24 23:08:30 2022 +0400
+++ b/src/stream/ngx_stream_proxy_module.c    Mon Nov 28 06:16:54 2022 +0100
@@ -435,7 +435,7 @@
     }

     u->peer.type = c->type;
-    u->start_sec = ngx_time();
+    u->start_msec = ngx_current_msec;

     c->write->handler = ngx_stream_proxy_downstream_handler;
     c->read->handler = ngx_stream_proxy_downstream_handler;
@@ -1679,8 +1679,8 @@
             && !src->read->error)
         {
             if (limit_rate) {
-                limit = (off_t) limit_rate * (ngx_time() - u->start_sec + 1)
-                        - *received;
+                limit = (off_t) limit_rate * (ngx_current_msec -
u->start_msec + 1)
+                        / 1000 - *received;

                 if (limit <= 0) {
                     src->read->delayed = 1;
diff -r 0b360747c74e -r a474ad7ca340 src/stream/ngx_stream_upstream.h
--- a/src/stream/ngx_stream_upstream.h    Thu Nov 24 23:08:30 2022 +0400
+++ b/src/stream/ngx_stream_upstream.h    Mon Nov 28 06:16:54 2022 +0100
@@ -127,7 +127,7 @@
     ngx_chain_t                       *downstream_busy;

     off_t                              received;
-    time_t                             start_sec;
+    ngx_msec_t                         start_msec;
     ngx_uint_t                         requests;
     ngx_uint_t                         responses;
     ngx_msec_t                         start_time;