MQTT data not received

[bandi22]

Issue:

No MQTT data is received in Grafana via TCP, despite the connection test being successful ("MQTT Connected") and the Grafana client showing up as 'Connected' in EMQX.

Messages are broadcasted in the broker:

"Explore data" option and dashboards show no data, time range is set to <1 minute. Subscription and the topic name is set correctly in the queries:

Explore data:

Dashboard:

Grafana logs show no apparent errors.

Environment:

• MQTT Datasource v1.1.0-beta.1 (installed from archive)
• Grafana v11.1.0 (Docker container)
• EMQX 5.7.1 (Docker container)
• MQTT protocol used: MQTT v3.1.1
• Connecting to MQTT via tcp/1883, no TLS, password only authentication
• Docker host is running on Oracle Linux 8.10

[jtowe1]

I am having the same problem

[nosovk]

The same problem :( I see connection in EMQX dashboard, but it seems that there is no subscription from Grafana.

[ArchiZ0]

I always got issue with this MQTT plugin and the "Explore data" feature. Try creating a dashboard and add a panel using your MQTT connection. Then enter the topic and switch to table view and you should see your data. From there, you will need to play with the visualization you want for a state change representation.

[nosovk]

We ended by running container with mosquito, that collects required topics and sends them to loki. Works like a charm.

[bandi22]

@ArchiZ0
Sadly, no luck. Table view shows no data either.

[ArchiZ0]

@bandi22 Sorry to hear that...

What is your use-case? How often data are sent in the topic? This MQTT plugin is for streaming data only as far as I know. There's no storage of any sort and small change like modifying the time range will reset the content.

We had to use a trick on the collector side to always keep a small buffer of data and when connection to topic are detected, we start by dumping that buffered data in the topic and then continue the live streaming.

In my case, we end up using this plugin as a real-time view for equipment metrics and we use it as a live debugging tools. I use variables to select an equipment dynamically and connect to the related topics.

For periodic / more historical oriented use-cases, we use a different datasource.

[nosovk]

Actually it's not very clear from documentation, that there is no storage inside. We moved to mosquito + Loki after realizing that.

[ArchiZ0]

@nosovk Well, is there any "client-side local storage" at all to any data sources in Grafana?.

I'm no Grafana expert but with all the data sources we've used so far, when you reload the page or change the time range, the data is re-read from the data source, like in your case, Loki... but it seems to be the case with others too, like InfluxDB or BigQuery, which are other data sources we're using.

What's different with MQTT is once the data is read by the client from a topic, the data is gone, by design... Even with the broker feature "retained messages", only the last one received in a specific topic is persisted at any time:

• EMQX : https://docs.emqx.com/en/emqx/latest/messaging/mqtt-retained-message.html
• HiveMQ : https://www.hivemq.com/blog/mqtt-essentials-part-8-retained-messages
• etc.

Reconnecting to the topic will simply read the last one and any subsequent data published.

[nosovk]

Yep, you have correctly described all. The main point is that users mostly want to connect their house temperature measurement to grafana. And its a bit unclear that it wouldn't work with that datasource. That's why there are so manu issues where people complain that something is not working, but its just not intended to work like they think.

[bandi22]

@ArchiZ0

Data is sent every few seconds or so from a machine, so I guess we could say it is live data, not historical. When I'm subscribed to the same topic on the broker with an MQTTX client, I can see the messages appearing, one after the other, live, but no data is shown in Grafana.

[ArchiZ0]

@bandi22 can you share the data you sent to the topic again please? This is very odd you don't see anything.