Re: unixsocket test of MariaDB (mysql) with unix_socket authentication plugin installed

Thanks for your replies.

I have just tried the password method. First in the database: CREATE USER
foo@localhost IDENTIFIED BY 'bar';

I left the unix_socket=OFF in my.cnf and monit was able to successfully
verify the socket is available using the test:

if failed unixsocket /tmp/mysql.sock protocol mysql username "foo"
password "bar" timeout 90 seconds then restart

Next I stopped mariadbd and removed unix_socket=OFF from my.cnf. After
restarting mariadbd Monit was still working ok and found the socket
available.

So the problem seems to be testing the socket without the creation of a
user under which Monit can log in. With the unix_socket plugin in
mariadbd this just won't work.

Checking my old server there's no anonymous connection allowed to the
database. But it also lacks the unix_socket authentication plugin. With
that combination Monit reports that the socket is available ok (although
I can understand that it's probably doing little more than checking it
exists). On the new server and with the unix_socket plugin Mariadb must
see the attempted anonymous login and fall through to the unix_socket
authentication check which then gives a definite 'No', causing the
Monit test to fail.

Definitely some gotchas here! But I can't blame the Debian Monit
maintainer - my monitrc file is pretty much unchanged for over 20 years
on a different system.

Many thanks, David