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GregBala-6003 avatar image
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GregBala-6003 asked tbgangav-MSFT edited

Application insights availabilty test showing false nagative

Hi, I have setup availability test using azure application insights and using uptrends.com.

I am getting a lot of errors in azure AI, from certain regions, that I cannot confirm in anyway - not via VMs deployed in that region, not via other services like uptrends.com ...

The error is :
A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond [...]:443

The failure occurs after just 20 seconds, when I have timeout configured at 120 seconds.

I've deployed VMs in the region from which availability test fail, and I can access the website just fine.

The endpoint being monitored, does a redirect, not sure if this matters, but just wanted to mention it.

It appears Availability Tests are giving me false negatives ... any ideas ?

azure-monitorazure-webapps-availability
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1 Answer

AnuragSingh-MSFT avatar image
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AnuragSingh-MSFT answered AnuragSingh-MSFT edited

Hi @GregBala-6003,

Welcome to Microsoft Q&A! Thanks for posting the question.

I see that you are trying to investigate the cause of the intermittent Availability Test failure for your application as reported in Application Insights. Based on my understanding, here are some of the insights that should help you troubleshoot it further (or gain additional insights about the failure):

1. In Application Insights"Availability" can you please select the failures and investigate the cause of failure as shown in the gif of this article: Troubleshooting. You can get to it by clicking on the test --> "Drill into..." Failed --> and clicking on details:

179260-image.png

The corresponding Troubleshooting report should help understand the step where the failure occurred. For example, in my sample scenario the URL is incorrect which results in DNS lookup failure:

179188-image.png

2. Regarding the "redirection", up to 10 redirects are followed in the availability test. For more details, please refer to this link

Since failure happens intermittently, it is possible that the issue occurs for a short duration (transient) and resolves on its own. It might not show up in your custom test through VM in that region unless the test runs periodically (similar to Availability test in Application Insights). To further narrow it down, please set the tests as shown in the image below:

179282-image.png

  • The first option (unchecked) ensures that we are only testing the reachability of web site which does not include the download duration of dependent resources.

  • The second option (checked) ensures that the test is performed thrice at an interval of 20 seconds (in case failure is reported).

Furthermore, as mentioned in the question, the issue only happens from certain regions, it would be interesting to get the details from tests above to help isolate the issue further.

Please let me know if you have any questions.

Please 'Accept as answer' and ‘Upvote’ if it helped so that it can help others in the community looking for help on similar topics.


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GregBala-6003 avatar image GregBala-6003 ·

Thanks for your help, but I do know how to check the nature of the failure and as mentioned, it is:

"A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond [...]:443"

This ONLY happens from azure availability test, and consistently from this location


179318-image.png



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AnuragSingh-MSFT avatar image AnuragSingh-MSFT GregBala-6003 ·

@GregBala-6003, thank you for the reply. Can you please share details about this applications:

  1. How is it hosted (Azure WebApps, Azure VM or on-premise etc.)

  2. Implementation details (is there a Load balancer or Gateway involved?)

  3. In which region/location is this hosted?


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GregBala-6003 avatar image GregBala-6003 AnuragSingh-MSFT ·

  1. on-prem, windows server, IIS

  2. load balancer - yes

  3. canada


I am also looking that the possibility that traffic is being blocked on our end



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