How to change active member in the pool without losing sessions?

Hello,

We have virtual server with 2 members in a pool where only other member at a time is active. When changing the active member, active sessions should still use the original member and the new connections go to the newly activated member. We change the active member by enabling and disabling them in the pool.

We are using the HTTP cookie insert as a persistence method and the cookie's name is LBSESSION. We have an iRule that removes the cookie at the logout:

  when RULE_INIT {
    set ::remove_lbsession 0
  }
  when HTTP_REQUEST {
    if { [HTTP::uri] equals "/jsp/ssl/logout.jsp" } {
       log "need to remove LBSESSION"
       set ::remove_lbsession 1
    }
  }
  when HTTP_RESPONSE {
    if {$::remove_lbsession==1} {
      log "Removing LBSESSION"
      HTTP::cookie remove LBSESSION
      HTTP::cookie insert name LBSESSION value "0" path "/"
      HTTP::cookie expires LBSESSION 0 absolute
      set ::remove_lbsession 0
    }
  }

The iRule works as planned and removes the cookie from the browser. Any way the big-ip do not respect that but continues to use the old member though it should select a new member, set LBSESSION cookie again and fire LB_SELECTED event at the next connection from the browser.

Does anyone have any ideas or solutions for our problem? We would appreciate some help on this.

Best regards,

Joel Mäkinen