MQTT Engine tags not updating

I’m trying to troubleshoot why my MQTT Engine topics are not updating. I’m using a MQTT client utility to view the topics published to the MQTT Server. The topics are being updated there on the server. However, the MQTT topics are there in the designer, but it’s not complete. The data does not show up.

After restarting the MQTT module in Ignition, we had to restart the MQTT Server in order for the MQTT Engine to resubscribe to the topics.

Is there a reason why we need to restart the MQTT Server in order to get Ignition’s MQTT module to work again?

I know the MQTT Server is working fine because I’m watching the topics being published. Viewing from another client says that I’m able to subscribe to the topics.

This seems to be happening a lot - once a week at the least. Anyone else having this issue?


Using MQTT Explorer, I can view topics are updating:

My guess would be that there is something in the MQTT message payload that Engine is not able to parse properly. Two potential issues…

  • The JSON payload is malformed in some way or contains some characters that our JSON parser is not handling by default.
  • The topic and/or a JSON payload property contains some character that Ignition doesn’t support in a tag/folder name; ‘.’ for example.

The easiest way to debug this further is to inspect the Ignition GW logs on the GW hosting MQTT Engine and see if Engine is logging errors about invalid JSON or invalid tag/folder name characters.

If you cannot find the errors easily, I recommend downloading your Ignition GW logs and sending them to If you can find the errors easily and need help understanding what they mean or how to proceed, we can try to continue to hash this out over this forum thread.

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