Introducing Permanent and Transient Error Handling in kubelet

Core Problem

The current implementation of the kubelet service in Kubernetes uses a retry mechanism to handle temporary errors. However, when a problem is deemed permanent, this approach can lead to wasted resources and unnecessary delays.

Solution & Analysis

To address this issue, we need to introduce a way to indicate permanent errors in the gRPC interface and provide support for marking pods as permanently failed in the kubelet.

# Define a new error type for permanent errors
from google.protobuf import wrapper_pb2

class PermanentError(wrapper_pb2.WrapperEnum):
  PERMANENT_ERROR = 1

// Introduce a new flag to indicate permanent failures in the kubelet
enum PermFailure {
    kPermFailureNone,  // default value
    kPermFailurePermanent,
};

// Modify the gRPC interface to return a PermanentError enum
google.protobuf WrapperEnum_PermanentError = google.protobuf.WrapperEnum_PermanentError(
    "PermanentError",  // namespace prefix
    & PermFailure::kPermFailurePermanent,
);

// Update the DRA driver to handle permanent errors correctly
public class DRAController : KubernetesController {
  public override void HandleFailure(KubeletEvent event) {
    if (event.GetPermanentFailure() == PermFailure.kPermFailurePermanent) {
      // Mark the pod as permanently failed and do not retry
      this_markPodAsFailed(event.GetPodName());
    } else {
      // Retry the operation with a temporary error
      this_retryOperation(event.GetPodName());
    }
  }

  public override void HandleTransientError(KubeletEvent event) {
    // Retry the operation with a temporary error
    this_retryOperation(event.GetPodName());
  }
}

Conclusion

By introducing permanent and transient error handling in the kubelet service, we can improve the overall reliability and efficiency of Kubernetes. The new implementation provides a clear distinction between permanent and temporary errors, allowing for more informed decision-making and resource allocation.

Reference

Source