Good afternoon, please tell me in the logs of one server (a cluster of 3 nodes) Varning-Error periodically appears:
2020-08-27T10:55:50.536154Z 0 [Warning] WSREP: unserialize error invalid protocol version 3: 71 (Protocol error)
With what it can be connected? What can be done to fix this?
That message usually appears when something external is probing the TCP port used by Galera (4567 by default) communication.
You can try out to reproduce it by telneting the port or scan it with nmap or similar.
If all cluster nodes run with same version of Galera plugin, that is unlikely to happen due to any legitimate cluster activity.