zookeeper | eMQTT1 eMQTT2 eMQTT3
Bridge
eMQTT1 --> eMQTT2
Cluster
eMQTT1 <--> eMQTT2
Cluster and Bridge
eMQTT1 eMQTT3 ----> eMQTT2 eMQTT4
Mnesia Cluster