Disable all nodes in pool if one node health check failed

I would look at writing an irule for the wideip on the gtm that uses nodes_up to determine if < 20 pool members are up. I've never used this, and the documentation seems a bit light on the subject, but something like this ~might~ work...

when LB_SELECTED {
  if { nodes_up [LB::server addr] < 20 } {
    LB::reselect
  }
}