[ASAP] Error keeps occurring without error logs (requests seem not to have been reached backend)

Hi.

Requests to our web app deployed on Azure App Service have resulted in errors. But error logs have not been output to ~_default_docker.log.

This issue happened irregularly and 500 error frequently occurred in the past 6 months.

Could someone help us resolve this issue?

I presume that these requests didn’t reach backends originally as there were no ERROR log/INFO logs on REST API (which is always explicitly output when request has arrived).

If requests aren’t delivered to the web app correctly, we’d like to clarify why the requests are not reaching the backend.

If not, we’d like to figure out why error logs were output to ~_easyauth_docker.log.

[Web app configuration deployed on Azure App Service]

Python3.11 / Gunicorn

[POINTS]

• The error log has been output in ~_easyauth_docker.log during the issue. (Recently even this log doesn't work)

2024_09_11_..._easyauth_docker.log:2024-09-11T04:06:14.577251450Z Failed to forward request to [http://169.254.129.6:8000]. Encountered a [System.Net].Http. HttpRequestException exception after 26.678ms with message: An error occurred while sending the request. Check application logs to verify the application is properly handling HTTP traffic.

• Normally, on Python 3.11/Gunicorn application, I confirmed that both the Python code ERROR/INFO log and the Gunicorn INFO log should be sent ~_default_docker.log as standard error output.
• I have checked the metrics of the web app during issues and it was not under a high load situation.
• The Python 3.11/Gunicorn app does not have an Azure authentication provider configured, but CORS (probably that's why easyauth is working).
• There is also no log of requests reaching the app on the Azure Application Insights requests log, which is implemented in the python code of the Python 3.11/Gunicorn app via OpenTelemetry.