MQTT

The MQTT input plugin retrieves messages and data from MQTT control packets over a TCP connection. The incoming data to receive must be a JSON map.

Configuration parameters

The plugin supports the following configuration parameters:

Key	Description	Default
buffer_size	Maximum payload size (in bytes) for a single MQTT message.	2048
listen	Listener network interface.	0.0.0.0
payload_key	Field name where the MQTT message payload will be stored in the output record.	none
port	TCP port where listening for connections.	1883
threaded	Indicates whether to run this input in its own thread.	false

Notes:

• buffer_size defaults to 2048 bytes; messages larger than this limit are dropped.

• Defaults for listen and port are 0.0.0.0 and 1883, so you can omit them if you want the standard MQTT listener.

• Payloads are expected to be JSON maps; non-JSON payloads will fail to parse.

TLS / SSL

The MQTT input plugin supports TLS/SSL. For the available options and guidance, see Transport Security.

Get started

To listen for MQTT messages, you can run the plugin from the command line or through the configuration file.

Command line

The MQTT input plugin lets Fluent Bit behave as a server. Dispatch some messages using a MQTT client. In the following example, the mosquitto tool is being used for the purpose:

Running the following command:

fluent-bit -i mqtt -t data -o stdout -m '*'

Returns a response like the following:

...
[0] data: [1463775773, {"topic"=>"some/topic", "key1"=>123, "key2"=>456}]
...

The following command line will send a message to the MQTT input plugin:

mosquitto_pub  -m '{"key1": 123, "key2": 456}' -t some/topic

Configuration file

In your main configuration file append the following:

fluent-bit.yaml

pipeline:
  inputs:
    - name: mqtt
      tag: data
      listen: 0.0.0.0
      port: 1883
      payload_key: payload

  outputs:
    - name: stdout
      match: '*'

fluent-bit.conf