backup resolver possible?

[medialy]

version: nginx 1.2.0 on centos 5.5 64bit

Nginx works as a http proxy. There are two resolver: ip1 and ip2. 
When ip1 fails on some url, nginx gives 502 error, but ip2 works on the url.

Can multi-resolver be used as master-slave? nginx may try slave resolver
when master resolver fails.


worker_processes      1;
 error_log             /dev/null crit;
 worker_rlimit_nofile  65535;
 events 
 {
   use epoll;
   worker_connections 65535;
 }
 
 http 
 {
   charset           off;
   override_charset  off;
   proxy_buffering   off;
   gzip              off;
   access_log        off;
   resolver          ip1,ip2;
   proxy_buffer_size 64k;
   proxy_buffers     4     64k;
   server
   {
     listen         1002;
     location /
     {
       proxy_set_header    Host             $host;
       proxy_set_header    Accept-Encoding  "";
       proxy_pass          http://$http_host$request_uri;
     }
   }
 }

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,229938,229938#msg-229938