title: What does the Resolver param in nginx do?
body: <p>I am using nginx as a reverse_proxy server with ELB. I am looking for explanation regarding the resolver value I set in the nginx.conf file. My nginx.conf:</p>
  
  <pre><code>http {  
     ...
  
     resolver x.x.x.x valid=30s;
  
     ...
  }
  
  server {
  
     ...
  
     set $elb "example.com";
  
  location / { 
      ...
  
      rewrite ^/(.*) $1 break;
      proxy_pass http://$elb/$1?$args; 
  
      ...
     }
     ...    
  }  
  </code></pre>
  
  <p>I followed this - <a href="https://www.ruby-forum.com/topic/6816375#1166569" rel="noreferrer">https://www.ruby-forum.com/topic/6816375#1166569</a> and set /etc/resolv.conf value as the resolver value and it works fine. What is standing behind this? </p>