Whitelisting Req/Conn Limiting

[SupaIrish]

Hello!

I'm want to limit req/connections but have certain requests skip or
whitelisted from the throttling.  I've found some prior threads that got me
this, which I think is working.  Here's just the relevant config.  Is this
the best/correct way to do this?  And if so I don't really understand the  
1 ""  part of the map block.  Can someone explain that?  The map docs
(http://nginx.org/en/docs/http/ngx_http_map_module.html#map)  aren't helping
me figure it out.  Thanks!

http {
    map $whitelist $limit {
      default $binary_remote_addr;
      1 "";
    }
 
    limit_conn_zone $limit zone=conn_limit_per_ip:10m;
    limit_req_zone $limit zone=req_limit_per_ip:10m rate=5r/s;
    
    server {
      set $whitelist "";
      if ( $hostname = some_url.com ) {
        set $whitelist 1;
      }
 
      limit_conn conn_limit_per_ip 10;
      limit_req zone=req_limit_per_ip burst=30 nodelay;
    }
  }

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,250510,250510#msg-250510