ngx http limit req : burst=0 cannot support more than 1000 RPS

Shrirang nginx-forum at
Wed Apr 16 14:30:24 UTC 2014

I am using "ngx_http_limit_req" module. After going through the code I see
that if "burst = 0" (i.e. not specified) then maximum rate limiting that can
be offered is 1000 RPS only. I have seen this in my stress test too.
I didn't see this in any documentation. Want to clarify if this is really
true or I missed something?

Reasoning :
1. Module expects uniform request arrival. Any request that breaks the
uniformity, will get rate limited.
2. Configured rate = 1000r/s. This means 1 request-per-ms.
3. If more than 1 request is received in same "ms" time, then only 1 request
is served. All other requests are rate limited.
4. For above configuration, if "burst=X" is configured, then "X" number of
requests are served while requests more than that will get rate limited.
5. If Configured rate = 2000r/s (i.e. 2 request-per-ms). If "burst=0" (i.e.
not specified), then too it supports only 1-request-per-ms rate. If 3
requests are received in same "ms" then only 1 is served and other 2 are
rate limited.

Posted at Nginx Forum:,249344,249344#msg-249344

More information about the nginx mailing list