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Snap type: | Write | |||||||||||||
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Description: | This Snap provides a convenient means for publishing JSON or String messages to a topic on an MQTT message broker. | |||||||||||||
Prerequisites: | [None] | |||||||||||||
Support and limitations: | Ultra pipelines: Supported for use Works in Ultra Pipelines.Spark mode: Not supported in /wiki/spaces/SD/pages/1437917 modeTask Pipelines. | |||||||||||||
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Settings | ||||||||||||||
Label | Required. The name for the Snap. You can modify this to be more specific, especially if you have more than one of the same Snap in your pipeline. | |||||||||||||
Topic | Required. A topic on the MQTT broker. Default value: [None] | |||||||||||||
Payload | Required. This can be a literal value or an expression which will be evaluated per document. If the evaluated value is a map or list, a JSON document will be published. To publish each entire incoming document, you would specify the document root ($). To publish a portion of each incoming document, you would specify that portion by designating this field as an expression and selecting that portion from your upstream schema. Default value: [None] | |||||||||||||
QoS | Required. An expression or literal value which must be able to be resolved as an integer with a value of 0, 1, or 2. The MQTT protocol provides three qualities of service for delivering messages between clients and servers: "at most once", "at least once" and "exactly once". Quality of service (QoS) is an attribute of an individual message being published. A subscribing client can set the maximum quality of service a server uses to send messages that match the client subscriptions. The QoS of a message forwarded to a subscriber thus might be different to the QoS given to the message by the original publisher. The lower of the two values is used to forward a message.
Default value: [None] | |||||||||||||
Retain | Required. True (selected) indicates that the MQTT server should retain a copy of the message. The message will then be transmitted to new subscribers to a topic that matches the message topic. False (not selected) indicates that this message should not be retained by the MQTT server. Default value: Not selected | |||||||||||||
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