iRule Context

Phil's right about the delayed binding. If you add an HTTP profile to the virtual server, the BIG-IP will parse the HTTP headers before establishing a server side connection. I don't think the server side context will ever be established in the HTTP_REQUEST event, so there probably isn't much use in checking to see if the server address exists in HTTP_REQUEST. For some details on event context, you can check this post (Click here).

Were you logging the virtual server IP in HTTP_REQUEST? That would always be available in the client side context using IP::local_addr.

If you want to log which server the connection was made with, you can just log the details in the SERVER_CONNECTED event. You'll need to save the HTTP::uri in the HTTP_REQUEST event as it's not available anymore in the SERVER_CONNECTED event. Here's an example based off of this codeshare entry (Click here:

  
  when HTTP_REQUEST {  
     set http_request_time [clock clicks -milliseconds]  
     set request_line "   
        [IP::remote_addr],\  
        [HTTP::method],\  
        [HTTP::version],\  
        [HTTP::host],\  
        \"[HTTP::uri]\",\  
        \"[HTTP::header value Referer]\",  
        \"[HTTP::header User-Agent]\",\  
     ]  
  }  
  when HTTP_RESPONSE {  
    set http_response_time [ clock clicks -milliseconds ]  
    log local0. "$request_log_line,\  
        [HTTP::status],\  
        [HTTP::payload length],\  
        [expr $http_response_time - $http_request_time]"  
  }  
  

Aaron