Master node of galera cluster is not in sync, how should I sync them?

Question

master node server id 10

SHOW STATUS LIKE 'wsrep_local_state_comment';
+---------------------------+----------------+
| Variable_name             | Value          |
+---------------------------+----------------+
| wsrep_local_state_comment | Donor/Desynced |
+---------------------------+----------------+

non primary server id 11

MariaDB [(none)]> SHOW STATUS LIKE 'wsrep_local_state_comment';
+---------------------------+--------+
| Variable_name             | Value  |
+---------------------------+--------+
| wsrep_local_state_comment | Synced |
+---------------------------+--------+

remote node, server id 20

MariaDB [(none)]> SHOW STATUS LIKE 'wsrep_local_state_comment';
+---------------------------+--------+
| Variable_name             | Value  |
+---------------------------+--------+
| wsrep_local_state_comment | Synced |
+---------------------------+--------+

but I also checked if these nodes have diverged,

MariaDB [(none)]> SHOW STATUS LIKE 'wsrep_last_committed';
+---------------+-------+
| Variable_name | Value |
+----------------------+----+
| wsrep_last_committed | 8 |
+----------------------+----+

all these 3 nodes returns the same value .

so I would presume they have not diverged but primary node is not in sync ? what does that mean ?

how can I fix this currently I get this error:

ERROR 1047 (08S01): WSREP has not yet prepared node for application us

I added wsrep_sst_donor=192.168.5.12 # this non primary node server id 11. in the dsynced master node my.cnf

but master still shows:

MariaDB [(none)]> SHOW VARIABLES LIKE 'wsrep_sst_donor';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| wsrep_sst_donor |       |
+-----------------+-------+

very scared if sudo systemctl restart mariadb would be safe !

Answer 1

Galera does not have a master node, only a collection of servers identified as primary.

Check all servers have the same galera UUID of the server. Work out which server data is most up to date. This should be the donor. Do get two running on the same UUID before restarting another.

You can copy the datadir of a shutdown mariadb instance as a backup.

See Recovering Primary Component in the documentation - https://dba.stackexchange.com/u/158002