App insights doubling some metrics

Harrison Henri 5

Hi everyone,

I have a NodeJS api deployed in a container app instrumented with App Insights:

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However, exploring the dashboards I noticed something strange. I get 8 requests failed: User's image

even when the logs only show 4 requests with status 400:

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Does anyone know what's happening?

Pranay Reddy Madireddy 1,575 Reputation points Microsoft Vendor

2025-01-23T15:48:40.08+00:00

Hi Harrison Henri
Just checking in to see if the below answer provided by @Stanislav Zhelyazkov helped. If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
Harrison Henri 5 Reputation points

2025-01-23T19:41:39.1733333+00:00

Thanks for your replies @Stanislav Zhelyazkov and @Pranay Reddy Madireddy ! Maybe I expressed myself poorly. I have 100% certainty that I only have 4 bad requests because I sent these requests myself using Postman. So, I don't understand why I have 8 failed requests presented in the dashboard.

1 answer

Stanislav Zhelyazkov 25,491 Reputation points MVP

2025-01-22T06:48:58.5966667+00:00
Hi,

I think you have Application Insights sampling enabled. In such case some similar requests (even failed ones) will be put into single record in the table. Each record in the requests table will have column itemCount with certain value. So when you count the records you need to count the sum of itemCount. For example:

requests | summarize count(itemCount)

Please "Accept the answer" if the information helped you. This will help us and others in the community as well.
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Harrison Henri 5 Reputation points

2025-01-22T12:22:03.57+00:00

Thanks for your reply @Stanislav Zhelyazkov ! Maybe I expressed myself poorly. I have 100% certainty that I only have 4 bad requests because I sent these requests myself using Postman. So, I don't understand why I have 8 failed requests presented in the dashboard.

Stanislav Zhelyazkov 25,491 Reputation points MVP

2025-01-24T07:47:09.92+00:00

Does the query I have posted actually shows 4 or 8?

Harrison Henri 5 Reputation points

2025-01-24T11:05:04.89+00:00

@Stanislav Zhelyazkov my issue is more related to the metrics that make up the App Insights dashboard, rather than the Log/Queries Hub. Therefore, both queries

requests | summarize count(itemCount)

requests

are gonna return the same 4 rows.

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Stanislav Zhelyazkov 25,491 Reputation points MVP

2025-01-24T12:39:38.6833333+00:00

Let me try to explain again. With Application Insights there are two types of metrics: Standard metrics and Log-based metrics.

If you go to metrics blade and try to choose namespace you will see those two types of metrics represented:

The view from your initial screenshot I think it is from the Overview page of the Application Insights and that view uses Standard metrics (Application Insights Standard metrics. When you execute query against requests table you basically you are querying Log-based metrics. More info on here: Metrics in Application Insights. As you can read in the document the Log-based metrics basically will not be full due to sampling working and not logging every request. Due to that you see the difference in what is shown in Overview as failed requests and what is shown by querying requests table. That mains that the count of records will always be higher on the Standard metrics compared to Log-based metrics. I do not what exactly you did to generate those failed requests so may be there was some confusion and more failed requests were generated or anyone else accessed the site and generated failed requests as well.

Harrison Henri 5 Reputation points

2025-01-24T13:59:17.8533333+00:00

@Stanislav Zhelyazkov thanks, but there is no confusion. I'm 100% sure I only hit the send button on Postman 4 times. In fact I tested it here again now and again I have two failed requests:

See that the metrics starts right:

and something happens and double the metric:

again here are the logs, trace samples, etc:

Stanislav Zhelyazkov 25,491 Reputation points MVP

2025-01-24T14:06:43.8466667+00:00

May be postman is doing something to cause that. All the above I have posted is the way it is. If it is not postman I would suggest to open support case as any abnormal behavior can only be investigated by support. I have tested on a test site of mine and doing requests via browser or using PS with Invoke-webrequest does not cause the problem you are describing. Requests are all correct.

Harrison Henri 5 Reputation points

2025-01-24T14:27:59.7333333+00:00

Yeah I'm gonna do that because this behavior makes no sense. I obtain the same result using cURL, so, I don't think there is something wrong with Postman. Thanks @Stanislav Zhelyazkov .
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App insights doubling some metrics

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