Servers and Sets can be configured for MQTT Transmission and MQTT Engine

MQTT Engine Server Sets were added in module release v4.0.22

Servers

The Servers tab allows you to configure a list of the MQTT Servers that the MQTT module should connect to.

Multiple MQTT Servers can be configured - often times more than one will be configured to handle fail-over in redundant or geographically distributed systems. 

Sets

The Sets tab allows you to configure server sets.

Each set represents a logical grouping of MQTT servers. 

When a set is referenced by a Transmitter configuration or an MQTT Engine configuration, a single connection to one of the servers in the set will be maintained. The other servers will act as failover in the case that a connection with the first is lost.

Servers will not be prioritized to force a connection to one server if multiple are available.

Server sets cannot have common elements meaning that a single MQTT server cannot be in more than one set.

From release 4.0.28, MQTT Transmission supports the option to randomize server connections. If enabled, the server to connect to will be randomly selected within the server set. Otherwise, a connection will be made to the next available server in the set.

Example

In the configuration below we have setup two server sets - one has two server configurations associated with it and one has three server configurations.

We have two Transmitter configurations each associated with one of the server sets.

A single connection is made to the first available server in each set. If this server becomes unavailable, MQTT Transmission will attempt to establish a connection with the next server in the set. If unsuccessful, it will continue to walk through the servers in the set until a connection can be made.




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