how to select a different virtual server's current pool?

Hi,

you could stick this in the irule (add in your other logic as needed)...This will check if the app_default has any active members if not use the shunt pool. So come upgrade time you just disable the app_default pool members. You could also apply this on the app VS.

if {[active_members app_default] >= 1}{
  pool app_default
  } else {
  pool app_shunt
  }

Another way without using separate pools is to create priority groups within the app_default pool, add the app_default servers in the higher priority group and the shunt ones in the other. In a steady state keep the shunt ones disabled/offline and when it's maintenence time enable the shunt pool members and disable the default pool members and drain the connections off as needed...

cheers

I have an idea, but don't know if it's possible or how to execute on it. If we could set a global variable (e.g.: ::app_pool) automatically via an iRule on the app vip - which is triggered whenever the pool is changed - I could then simply use that global var above and be done.

Is this possible?

Well, we ended up going with this solution:

iRule activated on app VIP:

when LB_SELECTED {
  set static::app_current_pool [LB::server pool]
}

Every time a pool member is selected for the a connection through the VIP, the global var 'app_current_pool' is set to the pool name.

The final iRule on the web VIP:

when CLIENT_ACCEPTED {
  HTTP::enable
}
when HTTP_REQUEST {
  if {[HTTP::header value "Upgrade"] equals "websocket"} {
    if { ( [class match [HTTP::uri] starts_with WebSocketUris ] ) } {
      if { [info exists "static::app_current_pool"] } {
        pool $static::app_current_pool
      else
        pool app_default
      }
      HTTP::disable
      return
    }
  }
}

Major change here is if the var exists, use it's value. Otherwise, run with default.

This has been tested and works.