Kubernetes: Why Do Some Ejabberd Pods Return an Empty Array on the get_user_rooms API Call?

Below is a list of steps and considerations to help narrow down the issue:

1. Confirm Environment Variable Consistency

Your configuration snippet only sets the database if the environment variable (DEFAULT_DB) is defined. Even though your logs show the config was loaded without error, it’s possible that some pods were started without the same environment variable value. Verify that each pod’s container spec includes the correct value. For example, you can inspect a pod’s environment like this:

BASHCopied
kubectl describe pod <ejabberd-pod-name>

Look under the “Environment” section and confirm that DEFAULT_DB is set consistently on every pod.

2. Compare the Running Configuration

Even if you see the normal startup logs, it’s a good idea to make sure that the configuration that ended up on each pod matches what you expect. To do this, you can extract the pod’s configuration from the Kubernetes API server and compare it with your intended config. For example:

BASHCopied
kubectl get pod <ejabberd-pod-name> -o yaml > pod-config.yaml

Compare the environment section in the YAML file with your deployment file to see if any differences could result in an unset or different DEFAULT_DB value.

3. Check Application-Specific Behavior

Since only one pod returns the expected result when running the get_user_rooms endpoint, the issue might also be within the application (ejabberd) rather than Kubernetes itself. Consider:

• Module or Cluster Behavior: If the pods form a cluster, ensure all members have correctly synchronized configuration. Network differences or race conditions during the cluster join might trigger inconsistent behavior.
• Internal Caching: Ejabberd may cache configuration or state information. Verify if there is a mechanism that would cause one pod to have stale data, especially if configuration reloads are handled differently.
• Logs and Debugging Tools: Use kubectl logs <ejabberd-pod-name> and potentially kubectl exec into the pods to run diagnostics/queries internal to ejabberd.

4. Revisit Deployment Configuration

Even if restarting the pod doesn’t change its behavior, double-check your deployment YAML or ConfigMap that injects the configuration. An overlooked misconfiguration—even a typo in the environment variable name—might cause some pods to run with default values rather than your intended settings.

Summary

• Make sure the DEFAULT_DB environment variable is defined and identical in every pod’s spec.
• Compare the live pod configuration (kubectl get pod -o yaml) with your intended configuration.
• Use logs (kubectl logs) and interactive debugging (kubectl exec) to further diagnose whether the problem is at the application layer or due to Kubernetes configuration discrepancies.

These steps should help you isolate whether the issue is coming from inconsistent deployment settings or an application-level behavior within ejabberd.