Is it possible to set non-volatile wsrep_provider_options, pc.weight by command?

Question

We are using MariaDB v10.5.15 and clustering of Galera-4 v26.4.11.

The cluster is in the weighted quorum mode so that the primary site has more votes than the non-primary. During a network outage, the primary site with more votes prevails and continues service without the other peer.

The system needs to undergo a regular disaster recovery examination, including switching the primary site to the other peer. So, we need to change the weight assignments for the design reasons explained above.

Within MySQL client, we can set pc.weight dynamically by command like set global wsrep_provider_options="pc.weight=2";. However, this command only changes the in-memory configuration. So, if reboot the host, the MariaDB will start again with the old value written in the configuration file /etc/my.cnf.d/server.cnf.

To make the new weights non-volatile, we need to edit the below part of the configuration file. And the edit is error-prone because the file contains many other items in the same line of wsrep_provider_options, with pc.weight in the middle.

[galera]
...
wsrep_provider_options="socket.ssl=true; socket.ssl_key=/etc/pki/galera/server-key.pem; socket.ssl_cert=/etc/pki/galera/server-cert.pem; socket.ssl_ca=/etc/pki/galera/ca-cert.pem; pc.weight=2"
...

I am wondering:

• Is it possible to set the pc.weight non-volatile without editing the configuration files?
• Otherwise, is it possible to separate pc.weight into another .cnf file while keeping the other items of wsrep_provider_options in the original file?

We highly appreciate your help and suggestions.

Answer 1

No pc.weight cannot be non-volatile without editing a configuration file.

If you put it into another configuration file and start the server with --defaults-extra-file=/path/to/other/file.cnf that would pick it up.

Another option is to start another node, even an arbitrator node, on the secondary site during DR/DR testing. That node might need more than a 2 weight.

How does the primary site know the weight of a node it hadn't seen? I'm not sure. So be careful.