Cheap SharePoint -> Wordpress fail-over help request

[keith]

We have nginx setup as a reverse proxy and on one of the backend servers 
we have a Sharepoint website that we want to failover to a Wordpress 
website hosted on another server if there's a problem with Sharepoint 
website. I've googled and red through books etc but can't we an example 
for this. I think i need "try_files" and some type of error code 
checking but havent been able to figure it out. Could someone advice ? 
Below is the type of thing that I think I am after.

Thanks for looking.
Keith

upstream primaryserver {  server 10.1.1.1:80; }
upstream secondaryserver {  server 10.1.1.2:80; }

server
{
   listen       80;
   server_name _;
   server_name_in_redirect  off;

     location /
   {
     try_files @sharepoint @wordpress;
   }
   location @sharepoint
   {
     proxy_pass http://primaryserver;
     proxy_set_header Host $host;
     proxy_connect_timeout 3;
     proxy_next_upstream error timeout;
   }

   location @wordpress
   {
     proxy_pass http://secondaryserver;
     proxy_set_header Host $host;
     proxy_connect_timeout 3;
     proxy_next_upstream error timeout;
   }

}