HTTP_Request and LB::Status

The following irule will achieve this:

 

 when CLIENT_ACCEPTED {
  set my_pool [LB::server pool]
}

when LB_FAILED {
log local0. "[active_members $my_pool]"
    if {  [active_members $my_pool] < 1 } {
        HTTP::respond 200 content {
        Apology Page
            We are sorry, but the site you are looking for is temporarily out of service
            If you feel you have reached this page in error, please try again.
         
        }    
    }
}
 

The event CLIENT_ACCEPTED is only needed to get the pool name, and then it checks on LB_FAILED, if really no member is there, then it sends back the maintenance page. Alternatively this will work also if attached to HTTP_REQUEST, but that means the code will run on every request, while LB_FAILED will only run if the systems fails to select a pool member. see also https://devcentral.f5.com/wiki/iRules.lb_failed.ashx