SQL database MariaDB setup in Installation Guide. The default install ignores 'max_connections' setting.

[Damian]

- [x] This is a doc addition request.

Installing on the CentOS it seems MariaDB ignores 'max_connections' variable.
In the accompanying documentation it is suggested to create file:

/etc/systemd/system/mariadb.service.d/limits.conf

with content:
[Service]
LimitNOFILE=10000

Then reload systemd:
# systemctl daemon-reload

Restart database
# systemctl restart mariadb.service

Details:
/usr/lib/systemd/system/mariadb.service

Reason:

The default database limits set by MariaDB, which is about 200, is quickly exhausted by querying the list of servers.
The visible result in logs is "Too many connections to database".
The 'max_connections' is computed based on 'open files' limit.
Because CentOS is systemd-based appropriate increase of limits should be done through systemd interface.

-----------------------------------
Release: 0.1 on 2017-03-24 15:12
SHA: a370d15d72958f0089527fc94bcfb3a34a5c5b92
Source: http://git.openstack.org/cgit/openstack/openstack-manuals/tree/doc/install-guide/source/environment-sql-database.rst
URL: https://docs.openstack.org/newton/install-guide-rdo/environment-sql-database.html

[Lana (loquacity)]

Looking closer at this now: I think that, while this may be true, it's probably not useful information for the Install Guide. The settings will work as given, and that is fine for a test/PoC install.