The mqtt_publish node

Publish data to a mqtt-broker. Incoming data is converted to JSON before sending.

If the save() parameter is given, every message first gets stored to an on-disk queue before sending, this way we can make sure no message gets lost when disconnected from the broker.

Note: This node is a sink node and does not output any flow-data, therefore any node connected to this node will not get any data.


def topic = 'top/track/pressure'


Using a lambda expression for the topic:

def topic_base = 'top/'

.topic_lambda(lambda: str_concat([topic_base, "type", '/', "measurement"])

Here the topic string is built with a lambda expression using the topic_base declaration, the string '/' and two fields from the current data_point. The topic string may be a different one with every data_point that gets published.


Parameter Description Default
host( string ) Ip address or hostname of the broker from config
port( integer ) The broker's port 1883 from config
user( string ) username from config
pass( string ) password from config
client_id( string ) mqtt client id, defaults to a combination of flow-id and node-id undefined
topic( string ) mqtt topic to use
topic_lambda( lambda ) mqtt topic to use evaluated via a lambda expression
qos( integer ) Quality of service, one of 0, 1 or 2 1
retained( is_set ) whether the message should be retained on the broker false (not set)
save( is_set ) send save (on-disk queuing) false (not set)
ssl( is_set ) whether to use ssl false (not set)

topic or topic_lambda must be provided.