Azure IoT Hub: Metric "Total number of messages used" seems incorrect

Question

The metric "Total number of messages used" seems incorrect because it decreased during the last week although the metric "Telemetry messages sent" is stable (as expected). The metric "Total number of messages used" is currently lower than "Telemetry messages sent" which does not make sense to me: Shouldn't "Total number of messages used" always be equal or higher than "Telemetry messages sent"?

Answer 1

Hello @DisplayName42 ,

welcome to this moderated Azure community forum.

The Azure IoT Hub counts the number of messages being sent by devices to the hub (D2C).

This is also seen in the Metrics:

Notice that this 'messages' can be confusing because an IoT Hub counts the number 4KB chunks. If a message has the size of 6KB, this is counted as two chunks.

I looked up the other metric also:

This 'total number of messages used' includes both D2C message and device twin changes, direct method calls, etc.

So, yes, the observation you made are a bit strange.

The metrics information is not reported live, there is a delay on the dialogs so we need to be patient ;-)

In the past, I have seen the that the Metrics were not updated correctly although the counting was done as expected. So, the Metrics were right a few days later.

Please check the metrics over the coming days and see if this is corrected.

If not, you can create an Azure support ticket so the support team can take a look at the backend.

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Answer 2

Thank you, @DisplayName42 , for connecting with us offline and sharing the information needed to work on this issue.

Additional diagnostics revealed that there are gaps in data ingestion into Azure Monitor. This is likely caused by provider registration ending in a bad state. Trying the following steps helped resolve the issue.

1. Navigate to the subscription on the Azure portal, find Resource Providers under the Settings section.
   1. Filter Microsoft.Devices and hit Re-register
   2. Filter microsoft.insights and hit Re-register
2. Wait for 24 hours for this registration to propagate and try querying the metrics

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