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.
Example
def topic = 'top/track/pressure'
|mqtt_publish()
.topic(topic)
.retained()
Using a lambda expression for the topic:
def topic_base = 'top/'
|mqtt_publish()
.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.
Parameters
| 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 | undefined |
topic_lambda( lambda ) |
mqtt topic to use evaluated via a lambda expression | undefined |
topic_field( string ) |
[since 0.19.9] path to a field in the current data-item, who's value should be used as the topic | undefined |
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 or topic_field must be provided.