Failover mechanisms for keystone LDAP backend are causing huge delays in Horizon if one LDAP server is down

Issue

• When multiple LDAP servers listed in the keystone domain config and if one of the ldap server is down then considerable delays and even authentication failures caused for users in Horizon even-though the other ldap servers are still available.
• Delays occur especially when the first server is down from the list of available ldap servers. Horizon performance can be dramatic, to the point that throws authentication errors.