Backup resolver possible?

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

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;
use epoll;
worker_connections 65535;

charset off;
override_charset off;
proxy_buffering off;
gzip off;
access_log off;
resolver ip1,ip2;
proxy_buffer_size 64k;
proxy_buffers 4 64k;
listen 1002;
location /
proxy_set_header Host $host;
proxy_set_header Accept-Encoding “”;
proxy_pass http://$http_host$request_uri;

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