nixos/services.mysql: on service init check for galera cluster

[6543]

When you init a new galera cluster node, it still goes through the init process of the mariadb. but then it syncs while the systemd postStart script wants to do the last "first time inits".

this had trubled me a lot till i figured it out.

the workaround is to let it fail the first time then manually delete the /var/lib/mysql/mysql_init file.
but I think we can do better.

the error you get other wise on startup is:

Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 2 [Note] WSREP: ================================================
Feb 10 12:00:54 DB_1 mysql-start[19234]: View:
Feb 10 12:00:54 DB_1 mysql-start[19234]:   id: ab262b68-e4b4-11ef-b301-2fd85ce810cd:470347
Feb 10 12:00:54 DB_1 mysql-start[19234]:   status: primary
Feb 10 12:00:54 DB_1 mysql-start[19234]:   protocol_version: 4
Feb 10 12:00:54 DB_1 mysql-start[19234]:   capabilities: MULTI-MASTER, CERTIFICATION, PARALLEL_APPLYING, REPLAY, ISOLATION, PAUSE, CAUSAL_READ, INCREMENTAL_WS, UNORDERED, PREORDERED, STREAMING, NBO
Feb 10 12:00:54 DB_1 mysql-start[19234]:   final: no
Feb 10 12:00:54 DB_1 mysql-start[19234]:   own_index: -1
Feb 10 12:00:54 DB_1 mysql-start[19234]:   members(2):
Feb 10 12:00:54 DB_1 mysql-start[19234]:         0: 619b4ff6-e8d6-11ef-925d-36d7fe26bb65, DB_2
Feb 10 12:00:54 DB_1 mysql-start[19234]:         1: ee2b4268-e8d2-11ef-a96d-fb7373fb82b6, DB_3
Feb 10 12:00:54 DB_1 mysql-start[19234]: =================================================
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 2 [Note] WSREP: wsrep_notify_cmd is not defined, skipping notification.
Feb 10 12:00:54 DB_1 systemd-timesyncd[1067]: Network configuration changed, trying to establish connection.
Feb 10 12:00:54 DB_1 systemd-timesyncd[1067]: Network configuration changed, trying to establish connection.
Feb 10 12:00:54 DB_1 systemd-timesyncd[1067]: Contacted time server 193.203.3.170:123 (3.nixos.pool.ntp.org).
Feb 10 12:00:54 DB_1 mysql-post-start[19416]: /nix/store/s4i8abwx7ra38jwqwirxw7m2j6aw1jlk-mariadb-server-11.4.4/bin/mysql: Deprecated program name. It will be removed in a future release, use '/nix/store/s4i8abwx7ra38jwqwirxw7m2j6aw1jlk-mariadb-server-11.4.4/bin/mariadb' instead
Feb 10 12:00:54 DB_1 mysql-post-start[19416]: --------------
Feb 10 12:00:54 DB_1 mysql-post-start[19416]: CREATE USER IF NOT EXISTS 'mysql'@'localhost' IDENTIFIED WITH unix_socket
Feb 10 12:00:54 DB_1 mysql-post-start[19416]: --------------
Feb 10 12:00:54 DB_1 mysql-post-start[19416]: ERROR 1047 (08S01) at line 1: WSREP has not yet prepared node for application use
Feb 10 12:00:54 DB_1 systemd[1]: mysql.service: Control process exited, code=exited, status=1/FAILURE
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] /nix/store/s4i8abwx7ra38jwqwirxw7m2j6aw1jlk-mariadb-server-11.4.4/bin/mysqld (initiated by: unknown): Normal shutdown
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: Shutdown replication
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: Server status change initialized -> disconnecting
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: Closing send monitor...
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: Closed send monitor.
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: gcomm: terminating thread
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: gcomm: joining thread
Feb 10 12:00:54 DB_1 mysql-start[19234]: 2025-02-12  2:00:54 0 [Note] WSREP: gcomm: closing backend

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