When you create an Active/Standby broker in Amazon MQ, you get 2 brokers with common shared storage, where all messages are available when failover happens in one broker. If you desire even higher availability, so that you have a broker available if two of your Amazon MQ brokers fail, then you can use Network of Brokers with a 3 node mesh. In this case, the brokers do not share storage, but you have 3 connected brokers so at least one will be available if two others fail. And all messages will be available when the brokers recover.
This feature is controlled by the following attributes in transportConnector. Both of the settings must be set to true to rebalance connections when a new broker is added or a broker fails.
updateClusterClients = true - This informs clients about new broker joining the network. Application code then choose to connect to new broker. rebalanceClusterClients = true - This automatically disconnects the client connection and reconnects the client to an active broker.