Why does Appinsights show a 200 Success for function and client is getting a 500.

Question

Why does Appinsights show a 200 Success for function and client is getting a 500.

mikefinch87 115

I have an AZure Function that pulls data from COSMOS, and returns as a json object. After putting Try/catch around OOM errors to generate a 400 series error with a message telling client to ask for less data. I am now occassionally getting azure to return a 200 response, but the client receives: <font color="#aa0000"> <h2>500 - The request timed out.</h2></font> The web server failed to respond within the specified time. APP Insights Logs |7:59:20.612 AM|Trace|Severity level: Information, Message: Executing 'Functions.

mikefinch87 115 Reputation points

2024-01-29T15:23:45.5433333+00:00

For fun tried from a Standard D8s v3 (8 vcpus, 32 GiB memory) machine in Azure, still failed. Not dependent on client size.
JananiRamesh-MSFT 29,236 Reputation points

2024-02-06T04:10:59.93+00:00

@******@gmail.com If increasing the resources allocated to your Azure Function did not resolve the issue, there may be other factors at play.

One possibility is that there is a bottleneck in the data retrieval process from Cosmos DB. You can try optimizing your query to reduce the amount of data being retrieved or to improve the performance of the query.

Another possibility is that there is a network issue between your Azure Function and Cosmos DB. I recommend you create a support ticket for a deeper investigation.

Do you have a support plan for this subscription? If not, I can have a one-time free support ticket created to have this specific issue investigated.

please let me know if you have any queries.

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mikefinch87 115 Reputation points

2024-01-29T15:23:45.5433333+00:00

For fun tried from a Standard D8s v3 (8 vcpus, 32 GiB memory) machine in Azure, still failed. Not dependent on client size.
JananiRamesh-MSFT 29,236 Reputation points

2024-02-06T04:10:59.93+00:00

@******@gmail.com If increasing the resources allocated to your Azure Function did not resolve the issue, there may be other factors at play.

One possibility is that there is a bottleneck in the data retrieval process from Cosmos DB. You can try optimizing your query to reduce the amount of data being retrieved or to improve the performance of the query.

Another possibility is that there is a network issue between your Azure Function and Cosmos DB. I recommend you create a support ticket for a deeper investigation.

Do you have a support plan for this subscription? If not, I can have a one-time free support ticket created to have this specific issue investigated.

please let me know if you have any queries.

Answer 1

The Azure Function is returning a 200 Success response code, but the client is receiving a 500 error with a message that the request timed out. One possible reason for this issue is that the function is taking too long to respond, causing the client to time out. To troubleshoot this issue, you can enable Application Insights and query for exceptions to identify any errors that may be occurring. Additionally, you can check the functionTimeout property in the host.json project file to ensure that the function is not taking longer than the specified timeout duration to execute.

References:

Answer 2

mikefinch87 115

Root Cause was that this was the FunctionLoadBalancer timing out in 230 seconds and returning the 502 while the function eventually finished working.

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Why does Appinsights show a 200 Success for function and client is getting a 500.

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