Using iRule to redirect F5 traffic based on Maintenance.

Tried to write iRule based on the question. Let us know if any question.

 when HTTP_REQUEST {
    if { [active_members [LB::server pool]] == 0 } {
         HTTP::redirect "http://www.google.com"  }
        }

    when HTTP_REQUEST_DATA {
     Define a string-type datagroup called dg_blocked containing words to be "Maintenance"
     if { [matchclass [HTTP::payload] contains dg_blocked] }{
        HTTP::respond 302 Location "https://www.google.com" }
      }

For general payload examination, payload collection is limited by memory allocation constraints to a 32MB maximum.