Mosquitto Clustered Architecture for High Availability(HA) and Load Balancing(LB)

•       Bridge Cluster – Set of active bridge nodes, broadcast incoming/published messages to remote nodes.

•       Remote Cluster – Set of active remote nodes, Each remote node sends incoming messages to all subscribers of that particular node.

•       HA Proxy Cluster – Set of HA proxy nodes in master-slave mode. Master is an active node handles all the requests in roundrobin fashion. Incase master goes down passive slave node gets elected as master.

•       Keepalived – Linux library runs as a daemon in both active and passive haproxy nodes. It performs failover on transport layer.

•       Virtual IP – Private network floating IP gets rotated in HA proxy cluster.  

•       Public IP – Public IP is mapped to Virtual Private IP.

•       Device/Gateway – Publish data to cluster over MQTT.

•       Cloud Application – Subscribe to cluster for device data over MQTT  

Descriptions –

For above setup we need total 6 machines. One machine for each haproxy master and haproxy slave, 2 machines for mosquito bridge nodes to handle mqtt publish traffic and 2 machines for mosquitto remote nodes to handle mqtt subscribe traffic (note - specific to my usecase).

Here, all publish messages from device and applications are handled on port 1883 and subscribe messages on port 1884.