Rate-limit

It is possible to limit the number of request in HAProxy by using almost any gathered data.

This topic is huge and complexe as it is possible to make everything, depending the needs.
A good introduction can be found on the blog of haproxy.com.

I have a simple cas where I only want to block an IP if the number of requests if too hight.

In a frontend:

stick-table type ip size 1m expire 10s store conn_rate(10s)

tcp-request inspect-delay 10s
tcp-request content track-sc0 src

tcp-request content reject if { sc_conn_rate(0) gt 10 }

Explications:

• 1st line: the table definition linked to this fronted (here with a time to live of 10 seconds)
• 2nd line: we must be sure to gather enough data (in the case of the IP, I think the delay can be lowered)
• 3rd line: a counter sc0 to follow the source IP (the counter is automatically linked to the previous table as it is in the same frontend)
• 4th line: the rule that allows to reject a request is the counter overrun the threshold (here 10 requests in 10 seconds)