how does nginx picks a resolver when there are multiple defined?

Question

How does nginx picks a resolver if you define several like:

...
resolver 108.x.x.x 120.x.x.x 19.x.x.x valid=30s;
...

Is it in a round-robin fashion? or there is some failover logic in there?

Answer 1

According to the nginx document http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver

Name servers are queried in a round-robin fashion.

They are using RR.