Huh, the socket is /tmp/systemd-private-838b9005a03d4e24b1649b6ecbae7bb3-mariadb.service-rKXi7L/tmp/mysql.sock

Unexpected!

For the record I ran into this at T219087 and basically my way around it was find /tmp -name mysql.sock, which returned something like /tmp/systemd-private-d6c71da3465641b3aa68e8390a2cc75c-mariadb.service-HPflMl/tmp/mysql.sock, then ran mysql -S <path>

Is there any specific reason to use 10.3 instead of 10.1?
@jcrespo is our package master, so he can probably provide more info about it. However, I believe 10.3 isn't fully ready yet from a package point of view, configuration+puppet as well.

Regarding the error itself, you might need to adjust your socket configuration to point to: socket = /run/mysqld/mysqld.sock (for both mysqld and for the client)

Adding @arturo who wrote a46d04c79dbb7d9690ea9998260dfaf06fc383b6 to install 10.3 on Stretch.

In T221463#5128430, @Andrew wrote:

Adding @arturo who wrote a46d04c79dbb7d9690ea9998260dfaf06fc383b6 to install 10.3 on Stretch.

I just used the most recent version in the repo. If 10.1 is better, let's just switch the version in the puppet class.

Change 505641 had a related patch set uploaded (by Arturo Borrero Gonzalez; owner: Arturo Borrero Gonzalez):
[operations/puppet@production] openstack: pdns: auth: use mariadb 10.1 on stretch

https://gerrit.wikimedia.org/r/505641

Change 505641 merged by Arturo Borrero Gonzalez:
[operations/puppet@production] openstack: pdns: auth: use mariadb 10.1 on stretch

https://gerrit.wikimedia.org/r/505641

We will at some point go for 10.3 but I don't think we are ready for it. It hasn't been properly tested yet, if you want to be an early adopter within WMF that's fine by me, otherwise I would suggest to go for 10.1 and migrate once we are a bit more sure about 10.3 :-)

wmf-mariadb103 doesn't exist, and if it exists, it won't work- we don't support it yet as we found some bugs and we are not working on those at the moment. The plan is only to support wmf-mariadb101 for stretch, and wmf-mariadb103 for buster (we stopped supporting wmf-mariadb for ubuntu and wmf-mariadb10 for jessie). If you need a roadmap, please ask us.

Having said that, the instructions on the body seem to me like a security concern, as no proper security hardening is done.

Also /tmp must never be used for socket location, because that is another security concern (everybody can write to /tmp, so it was banned at T148507), so both you and @Krenair might be doing bad practices regarding mysql installation (not sure about that), and that is why you may run into issues (systemd enforces no tmp access). We don't mind if you use wmf-mariadb1* (instead of the debian package), but please understand that if you do, that requires extra work, as the focus of wmf-mariadb* packages, patches and configuration is serving mediawiki on production -with automation provided outside of the installation (very low level setup)-, not a general-purpose package, easy to maintain by everyone.

Note that not supporting doesn't mean we don't accept and review patches if other people submit them for their use case, but we are not actively working on them at the moment. Alternatively, our MariaDB puppet module should be compatible with the Debian package for the most part if that is easier.