Nugget: Let Telegraf manage your InfluxDB Fields and Tags for you


Assume that some data is arriving to my Acquisition system in the form of the following JSON schema:

    "timestamp": "2020-09-02 13:10:00.000",
    "result": "GOOD"

In my case, the data is published to an MQTT Broker with the above mentioned JSON data as payload to a topic:



The following are the requirements:

  1. store the incoming JSON payload in InfluxDB
  2. instead of storing GOOD and BAD as fields, map them as GOOD -> 0 and BAD -> 1 where result should be stored as a tag and value (either 0 or 1) should be stored as field

Theoretically the InfluxDB Line Protocol String should look like:

systemStatus,result="GOOD" value=0 1599052200000
systemStatus,result="BAD" value=1 1599052200000

So Queries to other software components can be simply:

SELECT value from PROJ.autogen.systemStatus where result='GOOD'

Who You gonna call 📞? …. Telegraf

Here is how I solved the requirement:

  1. Connect telegraf to your MQTT Broker using the [[inputs.mqtt_consumer]] plugin and subscribe to the PROJ/system/status topic

  2. Use the json as the incoming data format. Telegraf Provides a wide range of Input Data Format

      data_format = "json"

    a. Use the name key of the JSON Payload as the Measurement Name using:

         json_name_key = "name"

    b. Store the result key of the payload as a field for the time being and make sure to store it as a string. For that simply use:

         json_string_fields = ["result"]

    c. Use the timestamp key of the payload to store the timestamp with Golang Format as follows:

          json_time_format = "2006-01-02 15:04:05.000"
          json_time_key = "timestamp"

    TOML Config:

            servers = [ "ssl://MY_MQTT_BROKER:8883" ]
            # Topics to subscribe to:
            topics = [
            # User Credentials and TLS Settings go here.
            # Incoming MQTT Payload is in JSON format with fixed schema
            data_format = "json"
            json_name_key = "name"
            json_string_fields = ["result"]
            json_time_format = "2006-01-02 15:04:05.000"
            json_time_key = "timestamp"
  3. Connect telegraf to your InfluxDB Instance using the [[outputs.influxdb]] or [[outputs.influxdb_v2]] plugin

    TOML Config:

        urls = ["https://<MY_INFLUXDBV1_INSTANCE:8086"]
        database = "PROJ"
        skip_database_creation = false
        # User Credentials + TLS Verify settings go here
  4. JUICY PART: Time to leverage the processors plugin to achieve our task:

    a. Let’s first use enum to map the respective values i.e. GOOD -> 0 and BAD -> 1 on our already available field result:

    TOML Config:

            order = 1
            field = "result"
            dest = "value"
                "GOOD" = 0
                "BAD"  = 1

    This configuration will be executed first due to order=1 and will map out field result to their respective numeric values into another field called value

    At this point, the Line Protocol String should look similar to:

     systemStatus result="GOOD",value=0.0 1599052200000
     systemStatus result="BAD",value=1.0 1599052200000

    b. Let’s use another processors plugin called converter to convert our field result into a tag.

    TOML Config:

            order = 2
                tag = ["result"]

    The order=2 takes care of telling telegraf to convert the field called result to a tag only after the enum mappings occur.

Complete Configuration File

Deployment via Docker

# assuming the above config file is in a directory called `telegraf`
docker run  -d --name=telegraf-converter -v $(pwd)/telegraf/telegraf.convert.toml:/etc/telegraf/telegraf.conf:ro telegraf:latest

See the logs using:

docker logs -f telegraf-converter


Why write scripts for things when you can write a TOML configuration in telegraf!! –

Lazy-ius Maximus

If you have more thoughts, improvements and criticisms then connect with me or send me an E-mail or a LinkedIn Message anytime!