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Using rate limitation for files smaller than the defined limit.

July 30, 2012 08:22AM
Hi!

We use nginx rate limiting function but realized that it does not work for files smaller than the limit specified in limit_rate directive. Analyzing the source code it turned out that forcing the limit is second based. We modified the source to be able to rate limit more precisely and it also works for smaller files.

Here is the patch:
leki@szunyog:~/src/agwlimit/nginx-1.2.2$ diff -u src/http/ngx_http_write_filter_module.c{.old,}
--- src/http/ngx_http_write_filter_module.c.old 2012-07-30 08:32:13.155354399 +0200
+++ src/http/ngx_http_write_filter_module.c 2012-07-30 13:55:01.074823215 +0200
@@ -211,8 +211,15 @@
}

if (r->limit_rate) {
- limit = r->limit_rate * (ngx_time() - r->start_sec + 1)
- - (c->sent - clcf->limit_rate_after);
+ if (ngx_cached_time->msec < r->start_msec) {
+ limit = r->limit_rate * (ngx_time() - r->start_sec - 1)
+ + r->limit_rate * (ngx_cached_time->msec + 1000 - r->start_msec) / 1000
+ - (c->sent - clcf->limit_rate_after);
+ } else {
+ limit = r->limit_rate * (ngx_time() - r->start_sec)
+ + r->limit_rate * (ngx_cached_time->msec - r->start_msec) / 1000
+ - (c->sent - clcf->limit_rate_after);
+ }

if (limit <= 0) {
c->write->delayed = 1;

As we tested the pathced nginx it worked fine. Could we use it in production or do you see any mistakes we made? Is there any reason you don't count on milliseconds?

Regards,
Gabor

Regards,
Gabor Lekeny
Subject Author Posted

Using rate limitation for files smaller than the defined limit.

leki75 July 30, 2012 08:22AM

Re: Using rate limitation for files smaller than the defined limit.

Maxim Dounin July 30, 2012 01:28PM

Re: Using rate limitation for files smaller than the defined limit.

leki75 July 31, 2012 11:18AM

Re: Using rate limitation for files smaller than the defined limit.

Maxim Dounin July 31, 2012 12:22PM

Re: Using rate limitation for files smaller than the defined limit.

leki75 August 22, 2012 09:24AM

Re: Using rate limitation for files smaller than the defined limit.

Maxim Dounin September 04, 2012 06:56AM



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