nginx.conf

upstream staticcontent {
        keepalive 128;
        server backend-01:80 max_fails=5 fail_timeout=15s;
        server backend-02:80 max_fails=5 fail_timeout=15s;
        server backend-03:80 max_fails=5 fail_timeout=15s;
        server backend-04:80 max_fails=5 fail_timeout=15s;
}

upstream dynamiccontent {
        keepalive 128;
	ip_hash;
        server backend-01:80 max_fails=5 fail_timeout=15s;
        server backend-02:80 max_fails=5 fail_timeout=15s;
        server backend-03:80 max_fails=5 fail_timeout=15s;
        server backend-04:80 max_fails=5 fail_timeout=15s;
}


server {
	listen 80;

	location ~* \.(ico|js|css|png|gif|jpe?g|swf|txt|html?|htc)$ {
		expires 7d;
		proxy_next_upstream error timeout invalid_header http_500 updating;
		proxy_cache_valid 200 7d;
                proxy_set_header Host $host;
                proxy_pass http://staticcontent;
	}

	location / {
		proxy_next_upstream error timeout invalid_header http_500 updating;
		proxy_set_header Host $host;
		proxy_pass http://dynamiccontent;
	}
}