iRule Event LB_FAILED - Triggered for Active Server-Side Connections?

Our application creates a "connection pool" to a VIP with 3 LDAP servers. These connections are created at application initialization.

The VIP's pool uses "Load Bal Method=Least Connections (member)" and "Priority Group Activation=Less than 1". The pool members have Priority Group values of: ldap-01 : 100 ldap-02 : 90 ldap-03 : 80

When the application is started All of its 'connection pool' connections go to ldap-01, which is what we want. And of course we want them to stay there unless ldap-01 becomes unavailable.

The application does not handle errors well, but cannot be changed (easily). I am trying to minimize the chance of the app seeing an error when we stop ldap-01 for maintenance. I want the VIP to switch to ldap-02 for an 'in flight' transmission that suffers a time-out or RST.

My question is this, Is is possible to use an iRule, such as the one below, to trigger selection of ldap-02 if the already established connection has a error, such as timeout or RST, when ldap-01 is stopped?

Reading the description of LB_FAILED I think the answer is No. LB_FAILED will fire when the initial VIP pool member connection is attempted (SYN) but that is the only connection-related condition that triggers LB_FAILED(?) If the server-side connection suffers a transmission time-out or an RST that will not trigger LB_FAILED, correct?

We have a 2 second health check, but the app is super busy and there are essentially always active requests.

If the iRule below is not the right approach is there another iRule event that will allow an LB::reselect to chose ldap-02 and re-send the request?

=== candidate iRule === when CLIENT_ACCEPTED { set retries 0 } when LB_FAILED { if { $retries < [active_members [LB::server pool]] } { LB::reselect incr retries } }