Login with LDAP authentication takes 5 seconds

[Andreas Schmid <user462411@xxxxxxxxx>]

Hi,

I configured my PostgreSQL 10 DB on Debian 9.2 with LDAP authentication (simple bind mode). While this basically works, it has the strange effect that the first login with psql takes around 5 seconds. When I reconnect within 60 seconds, the login completes immediately.

The LDAP server is behind a firewall. So for a test, in pg_hba.conf I put the LDAP servers IP address instead of its DNS name (for parameter ldapserver). Like that, all logins complete immediately. But in general I prefer specifying the DNS name rather than the IP.

When I checked on the DB machine with the following commands

host my.ldap.server.org

dig my.ldap.server.org

both always returned the host name and IP address of the LDAP server immediately.

Does anyone of you have an explanation for this, or a hint, where I could do some further investigation?

Thanks,

Andy