Mastering Nginx

Chapter 6

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server {

resolver 192.168.100.2 valid=300s;

}

Table: Name resolution directives

Directive Explanation

resolver Configures one or more name servers to be

used to resolve upstream server names into

IP addresses. An optional valid parameter

overrides the TTL of the domain name

record.

In order to get NGINX to resolve an IP address anew, place the logical name into
a variable. When NGINX resolves that variable, it implicitly makes a DNS look-up

to find the IP address. For this to work, a resolver directive must be configured:

server {

resolver 192.168.100.2;

location / {

set $backend upstream.example.com;

proxy_pass http://$backend;

}

}

Of course, by relying on DNS to find an upstream, you are dependent on the resolver

always being available. When the resolver is not reachable, a gateway error occurs.
In order to make the client wait time as short as possible, the resolver_timeout

parameter should be set low. The gateway error can then be handled by an error_
page designed for that purpose.

server {

resolver 192.168.100.2;

resolver_timeout 3s;

error_page 504 /gateway-timeout.html;