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: 159.223.105.21 galera2: 137.184.78.182 galera3: 137.184.65.171
The my.cnf line for wsrep_address should read as follows:
wsrep_cluster_address="gcomm://159.223.105.21,137.184.78.182,137.184.65.171"
It is then trivial for you to have your fourth server (say, galera4: 161.35.120.111), have a my.cnf that reads as follows:
wsrep_cluster_address="gcomm://159.223.105.21,137.184.78.182,137.184.65.171,161.35.120.111"
Now, …
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