It appears, from my testing, that ejabberd's ldap authentication mechanism suffers the same deficiency as the external authentication script mechanism - in that it performs authentication requests serially, which leads to authentication backlogs if a lot of requests come in simultaneously (e.g. a node is restarted) even if each individual request is processed very fast. Is this true, or am I mistaken?
Is there an authentication mechanism in ejabberd that is performed in parallel?
Re: parallel authentication
Just set your server multiple times in the config:
{ldap_servers, ["host", "host", "host", ...]}.
But I'm not sure that helps too much.