least_conn not working for me

Maxim Dounin mdounin at mdounin.ru
Wed Dec 23 17:14:42 UTC 2020


On Wed, Dec 23, 2020 at 10:27:44AM -0500, Kenneth Brooks wrote:

> I have a fully working config doing loadbalancing over 2 upstream servers.
> I want to use "least_conn"
> When I put least_conn in, it still is doing round robin.
> I can confirm that other configs like "weight' and "ip_hash" are working as
> expected.
> Is there some other configuration/setting that also affects whether
> least_conn is honored?

The "least_conn" balancing method is equivalent to round-robin as 
long as all configured upstream servers have equal number of 
connections opened.  That is, if you are seeing nginx is "doing 
round robin", most likely this means that there isn't enough 
active connections for least_conn to be different from 

Note well that "number of connections" applies to a single nginx 
worker process, and if there is more than one worker, least_conn 
might not see all the connections (unless you've configured nginx 
to share information about upstream servers between worker 
processes, see http://nginx.org/r/zone).

Maxim Dounin

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