How do I determine how long a message from inject node takes to go through my system and output to a Grafana dashboard

General
1

Hi there,

I am using inject nodes to simulate a sensor which is producing messages to MQTT, then to Kafka, InfluxDB and finally Grafana. How do I determine how long a message from inject node takes to go through my system and output to a Grafana dashboard.

Thanks in advance,
Cian

2

Interesting question. I believe this is determined mostly by the polling period of grafana doing a query and how you do the display (again by a refresh timer?)
If not I would try to 1st record a timestamp at the first node. And set up a alarm in grafana (I played around only a little bit) and try to get this back into node-red to trigger a second timestamp.

3

What have you got the refresh period set to in the grafana dashboard? This is likely to be very much the largest time. The rest should be small fractions of a second generally, except that occasionally it may take a little longer due to nodejs garbage collection, and assuming that you are using a non realtime OS such as Raspbian then other things on the system may hold up node red.

4

Hey, thanks for your suggestion I will check it out now. Nice work!

5

I have the refresh set to 5 secs. That is the lowest option. Does Grafana query every 5 seconds and timestamp the points repectively?

6

The timestamps come from the data in the influx database.
As a matter of interest why are you using Kafka between mqtt and influx, you could write to influx directly from node-red. Or are the various components on different system.

7

Influx and grafana is more intended for historic data. Why not passing the data from mqtt to Node-Red and use linear gauge (vertical) for ā€œreal timeā€ visualization of the most recent data. Place your grafana chart next to it for data older than 5 sec data. Or use the dashboard chart and grafana only for analysis.

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8

I am using Kafka to send streams to different components. As it scales horizontally I thought it might be worth using. Especially, if I intend to extend it in future. I have a real-time stream and a offline stream which saves a back-up to Hadoop etc (I am only experimenting)

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