Rebalancing connections

There's a way in case it's HTTP traffic and pool nodes are in different priority groups - to force connections to reconnect to higher priority node once it comes back online.

We use this simple irule which checks on every HTTP response whether it's delivered from highest available priority group - if not we call HTTP::close which gracefully closes the connection after response is delivered, forcing client to establish a new connection. As this is graceful (not a TCP reset or similar), it's not impacting.

when HTTP_RESPONSE {
  if {[HTTP::is_keepalive]} {
    set serverip_active 0
    foreach { pmem } [active_members -list [LB::server pool]] {
      if { [IP::addr [IP::server_addr] equals [getfield $pmem " " 1]] } {
        set serverip_active 1
        break
      }
    }
    if { $serverip_active equals 0 } {
      HTTP::close
    }
  }
}

To rebalance connections within the same priority group, one would need to check number of connections to all nodes and compare them with configured ratio. As far as I can tell there's no easy way to achieve that, number of connections would need to be tracked externally (in session table or istats).