Kubernetes pod stops sending HTTP request abruptly

We have 2 dotnet APIs – A and B, containerized and deployed on a Kubernetes cluster. Both pods are on different nodes. When a POST call is made to API A, A sends a GET call to B.

Now everything was up and running from past 3 days, and no deployments were made. Suddenly a POST call to API A stops sending the GET call to B.

All direct calls to B (from browser or Postman) are successfully executing. I exec into POD A and tried the GET call to B using curl and even that was successful.

I ran API A locally, and tested, everything was working fine.

We ran into this issue quite a few times and the quick fix is to restart the deployment/pod A and everything starts working fine again. But I’m not able to find the root cause. Is there any way I can debug this scenario?

About the application:

We send a POST request to a method M in API A passing a JSON in the body. One of the field (“_id”) of json is retrieved and then a GET call is made to API B from within the method M using _id.

Everything was working fine but now that GET call stopped going. Nothing changed in infrastructure part nor in the code. It just stopped working abruptly.

Source: StackOverflow