NodeRED and InfluxDB - One Measurement more fields

[Egnos]

Hi all, I'm new to the Forum and also to NodeRED. I hope you can help me:
I created a container with NodeRED Ver. 1.3.4 and I'm doing various experiments.
One of them is to extrapolate the payload of this request from this message https://api.waqi.info/feed/A144943/?token=8f3999b079d169a52edadec8124708c605e63e90

I managed to identify the fields I need and they are:

• payload.data.aqi
• payload.data.iaqi.pm10.v
• payload.data.iaqi.pm25.v

I managed to write these values in InfluxDB but each with a different "measurement".
I would like these values to be written under one "measurement" with 3 fields (Time, AQI, PM10 and PM25).

To write to InfluxDB I use "node-red-contrib-influxdb".

I've read a lot on the net (discussion and official guides...) and I've managed to do a lot of things but I'm missing the last piece that I couldn't understand... could you help me?

Thank you all.

[jodelkoenig]

Just send the data to the same influxdb out node. create on entry and assign your assignment there.

[Egnos]

Hi @jodelkoenig, could you show me how to do it?
Which nodes should I use?
What code should I write to isolate these fields and tell InfluxDB to create a "Measurement" with 4 fields (Time, AQI, PM10 and PM25)?

Thanks!

[jodelkoenig]

This I send to the one influxdb out node via different function nodes:

msg.payload = [{
    light: state
},
{
    room: flow.get("name"),
    category:"Beleuchtung",
    device:"Decke"
}];
return msg;

light could be Time, AQI, PM10 and PM25
room, category, device could be any tag you like

[Colin]

Or, if you don't have any tags then you just need the payload to be a simple object containing the fields. Something like this in a function node

msg.payload = {
  PM10:  msg.payload.data.iaqi.pm10.v,
  PM25:  msg.payload.data.iaqi.pm25.v,
  etc...
}
return msg

Or you can do the same in a Change node.

[Egnos]

I try to write what I understand.
I have:

• an "INJECT" node that acts as a trigger;
• an "HTTP REQUEST" node to capture the msg (return: a parsed JSON object)
• an "FUNCTION" node to tell InfluxDB how to save the data;

msg.payload = [{
    aqi: state,
    pm10: state,
    pm25: state
},
{
    room: flow.get("name"),
    category:"Beleuchtung",
    device:"Decke"
}];
return msg;

• finally an "INFLUXDB OUT" node to save the data in a certain DB with a certain "Measurement"

Is the flow correct?
Is the code in the "FUNCTION" node correct?

Thank you very much!

[jodelkoenig]

You should skip:

,
{
    room: flow.get("name"),
    category:"Beleuchtung",
    device:"Decke"
}

or adopt correspondingly if you would like to use tags. You might not need it, then just delete it from your code.

EDIT:

Or ... just take Colin's example

[Colin]

I didn't say previously, but you don't need to provide a time to influx, if the data is for the current time. Influx will add it automatically.

In addition, I recommend watching this playlist: Node-RED Essentials. The videos are done by the developers of node-red. They're nice & short and to the point. You will understand a whole lot more in about 1 hour. A small investment for a lot of gain.

[Egnos]

I tried to put the code you suggested in the "FUNCTION" node:

msg.payload = {
  PM10:  msg.payload.data.iaqi.pm10.v,
  PM25:  msg.payload.data.iaqi.pm25.v,
  AQI:   payload.data.aqi
}
return msg

...but i have this error:

21/12/2022, 20:32:16node: Formatting
function : (error)
"ReferenceError: payload is not defined (line 4, col 10)"

[jodelkoenig]

Check line 4 and compare it to line 3 and 2. I assume you want to refer to msg.payload.data.aqi, right?

[Egnos]

Thanks, now work!!
I added msg. before payload.data.aqi
It's very strange because if I copy the path from the original message payload printed by NodeRED (I followed the official guide...) I have this: payload.data.aqi, without msg. front!

[Colin]

It gives you the path within the message.