Error: [ldap] All ldap connections are in use

[Phil Brown]

We have started seeing problems our radius server with the Error
"Error:   [ldap] All ldap connections are in use"

We have  increased the "ldap_connections_number" from 5 to 20 which has
largely resolved the issue.

we now receive over 100,000 authentications a day, is there any guide
to "ldap_connections_number"  for the number of authentications or
should we just keep increasing the number until the issue goes away