priority LB - maybe better suited to iRule?

Troubleshooting w/o logs is tough ... not knowing how to turn on logging ... even tougher! Can you clue me in on how to add some logging - that would be great.

I think LB_FAILED is being triggered - this works -

when CLIENT_ACCEPTED {pool main_pool}
when LB_FAILED {
      pool failover_pool
      persist none
      LB::reselect
}

must be losing it in the if clause:

if { [LB::server pool] eq "main_pool" and [active_members main_pool] == 0} {
      pool failover_pool
      persist none
      LB::reselect

I can probably live w/o that if clause - and it might make the irule faster/etc.

I still see the BIGIP cookie get set - however when my main_pool node members come back traffic doesnt persist to the failover_pool ... so that works too.