Make mariadb replicas to work with 10.2 to 10.7 #83

stronk7 · 2022-08-24T19:24:21Z

This must be merged AFTER #82 !!

The code used here is 99% the same than the mysql one. But finally
I've decided to copy it all over own mariadb.d directory.

$ diff -r mysql.d mariadb.d
diff -r mysql.d/master/docker-entrypoint-initdb.d/01_privileges.sql mariadb.d/master/docker-entrypoint-initdb.d/01_privileges.sql
1c1
< CREATE USER 'replication'@'%' IDENTIFIED WITH mysql_native_password BY 'replication';
---
> CREATE USER 'replication'@'%' IDENTIFIED BY 'replication';

The only difference is when creating the replication database user
because the MySQL sentence:

CREATE USER 'replication'@'%' IDENTIFIED WITH mysql_native_password BY 'replication';

Doesn't work with MariaDB. In fact, since MariaDB 10.2 the
mysql_native_password is the default authentication plugin
so it doesn't need to be specified. So this works the same:

CREATE USER 'replication'@'%' IDENTIFIED BY 'replication';

A working alternative is also:

CREATE USER 'replication'@'%' IDENTIFIED WITH mysql_native_password USING PASSWORD('replication');

But I've gone with the simple one because it's future better.

As said, everything else is 100% the same, but better split that making
complicated conditionals to get both working with the same config files.

This fixes moodlehq#80. It has been detected that MySQL main/replica configurations have stopped working. My personal bet is that some changes in the MySQL images have leaded to that, or maybe they were working for MySQL 5.6 and never have worked to 5.7. NVM, this commit just makes them back to work for both 5.7 and 8.0, that are the currently "supported" MySQL databases. Note that, after this PR, we'll be checking the MariaDB main/replica configurations because they may need similar changes. Also, while I've tested the solution locally, we are lacking any own CI for this product, so I've created an issue about that: moodlehq#81 Finally, here there are the explanations about the changes performed: 1. Moved the bin logs from /var/log/mysql to /var/lib/mysql . Reason being that the former directory doesn't exist anymore in MySQL 5.7 and up (and also, that the binary logs are better with data than with logs). 2. Removed the 'multi_admin' user related stuff. Not needed at all. 3. Minor changes to moodle and root GRANT/IDENTIFIED stuff because of changes in MySQL 8 (already deprecated in 5.7). Use ALTER USER instead. 4. Use IDENTIFIED WITH mysql_native_password (the old password schema), because MySQL 8, when using the new hashed schema requires communications between the hosts to be encrypted. We don't need that extra complexity and while it can be disabled as part of the CHANGE MASTER TO command... it cannot be disabled for MySQL 5.7. SO the only option working in both versions is the used one (force old passwords schema for the replication user). 5. Remove the need of stopping and starting the temp server in the replica. All the commands can be executed with the temp server running and then the container entrypoint manageing itself will stop the temp server and start the final one. 6. Stop needing gosu completely. Now the replica conf files are made available via volume mount (like the standalone or main cases). And that's all. The changes are small and subtle, but each one is for a good reason, I think.

The code used here is 99% the same than the mysql one. But finally I've decided to copy it all over own mariadb.d directory. The only difference is when creating the replication database user because the MySQL sentence: CREATE USER 'replication'@'%' IDENTIFIED WITH mysql_native_password BY 'replication'; Doesn't work with MariaDB. In fact, since MariaDB 10.2 the mysql_native_password is the default authentication plugin so it doesn't need to be specified. So this works the same: CREATE USER 'replication'@'%' IDENTIFIED BY 'replication'; A working alternative is also: CREATE USER 'replication'@'%' IDENTIFIED WITH mysql_native_password USING PASSWORD('replication'); But I've gone with the simple one because it's future better. As said, everything else is 100% the same, but better split that making complicated conditionals to get both working with the same config files.