A common question we get is: can I add a node to my Galera Cluster without restarting the entire cluster? The simple answer is YES.
A lot worry about the fact that you do list servers that are part of the cluster within your my.cnf, and this file is not reloadable in a dynamic fashion. Fret not, though, because as long as your my.cnf has one active cluster member (the DONOR), you can have it be the JOINER.
If for example, you have 3 nodes: galera1: 126.96.36.199 galera2: 188.8.131.52 galera3: 184.108.40.206
The my.cnf line for wsrep_address should read as follows:
It is then trivial for you to have your fourth server (say, galera4: 220.127.116.11), have a my.cnf that reads as follows:
Now, …[Read more]