Kubernetes Namespaces play a crucial role in managing resources within a Kubernetes cluster. They allow for the organization and isolation of resources, enabling efficient management of large-scale applications. However, occasionally, Kubernetes Namespaces can become stuck in the Terminating state, preventing us from creating new resources or updating existing ones. In this article, I will delve into various potential causes for this behavior and outline some strategies, for you to overcome these obstacles.

Diagnosing and Troubleshooting Stuck Namespaces

Before diving into the potential causes, it is essential to diagnose and troubleshoot stuck Namespaces using Kubernetes events and logs. Common patterns and error messages may simply present you with the underlying issues.

The first step is always to retrieve events within the Namespace:

kubectl get events -n <namespace_name>

Once you have identified an Issue, you can review logs of related resources, such as Pods, to identify potential issues:

kubectl logs -n <namespace_name> <pod_name> [<container_name>]
# to view the logs of all containers of a pod
kubectl logs -n <namespace_name> <pod_name> --all-containers
# to follow the logs in real-time use
kubectl logs -n <namespace_name> <pod_name> [<container_name>] --follow
# for already deleted container logs use 
kubectl logs -n <namespace_name> <pod_name> [<container_name>] --previous

Cause 1: Finalizers

Finalizers are an essential aspect of the Kubernetes resource lifecycle, ensuring that specific actions occur before an object is deleted. These actions might include releasing external resources, cleaning up associated data, or notifying other components of the deletion. Kubernetes uses finalizers to implement graceful deletion for resources, allowing them to complete any required cleanup tasks before the object is permanently removed.

However, finalizers can sometimes prevent a Namespace from being deleted if the required cleanup tasks are not completed or if a custom finalizer is implemented incorrectly. In such cases, it’s crucial to identify and remove finalizers within the Namespace to allow for its smooth deletion. Custom finalizers or non-standard resources, such as Custom Resource Definitions (CRDs), might also be preventing the Namespace from being deleted.

In order to identify and address finalizer-related issues in a Namespace:

  • List the Namespace’s configuration in JSON format to find existing finalizers:
kubectl get namespace <namespace_name> -o json
  • examine the finalizers field under metadata to identify any finalizers associated with the Namespace.

If the finalizers appear to be standard Kubernetes finalizers, investigate the Namespace’s resources and their statuses to identify any issues preventing the finalizers from completing their tasks.

As for custom or non-standard finalizers, review the associated components or controllers responsible for implementing the finalizers. Ensure they are functioning correctly and completing their intended tasks. Fix any issues or misconfigurations that might be preventing the finalizers from completing.

  • If the finalizers are still causing issues, you can consider removing them manually as a last resort. Be aware that manually removing finalizers can result in incomplete cleanup tasks, potentially leaving orphaned resources or data:
kubectl patch namespace <namespace_name> -p '{"metadata":{"finalizers":[]}}' --type=merge

This command will remove all finalizers from the Namespace, allowing it to be deleted. However, use this approach cautiously and only when necessary, as it bypasses the standard deletion process.

Cause 2: Admission Webhooks

Admission webhooks, including both mutating and validating types, play a vital role in the Kubernetes API request processing pipeline. These webhooks intercept and modify or validate requests, ensuring they meet specific criteria before being processed further. However, they can sometimes interfere with the deletion of resources and cause a Namespace to become stuck in the Terminating state. To address this issue, follow these steps:

  • List the configured admission webhooks in your cluster to identify any that might impact the Namespace you are trying to delete:
kubectl get mutatingwebhookconfigurations,validatingwebhookconfigurations

  • Examine the listed webhooks and their configurations to determine if any of them are preventing the deletion of resources within the Namespace. For example, a webhook might be configured with a rule that prevents the deletion of specific resources or returns an error upon deletion attempts.

  • Temporarily disable or modify the problematic webhook configuration to allow the Namespace to be deleted. Be cautious when disabling webhooks, as it may have unintended side effects on other resources in the cluster.

For instance, to disable a validating webhook temporarily, you can edit its configuration:

kubectl edit validatingwebhookconfigurations <webhook_configuration_name>
  • Set the failurePolicy to Ignore and save the changes. This action will cause Kubernetes to ignore any errors returned by the webhook and proceed with the deletion process.

NOTE: After resolving the issue and successfully deleting the Namespace, remember to re-enable or restore the webhook configuration to its original state to maintain the intended functionality of your cluster.

By identifying and addressing any issues related to admission webhooks, you can efficiently resolve Namespace deletion problems and ensure a smooth Kubernetes experience. Keep in mind that modifying webhook configurations will have broader implications on your cluster, so exercise caution and thoroughly understand the impact of any changes before implementing them.

Cause 3: Cluster Stability and Health

In some cases, a Namespace may be stuck due to underlying issues with the Kubernetes cluster itself. To ensure the cluster is healthy:

  • Check the health of the cluster components:
kubectl get componentstatuses

A healthy output should look like this:

Warning: v1 ComponentStatus is deprecated in v1.19+
NAME                 STATUS    MESSAGE   ERROR
scheduler            Healthy   ok        
controller-manager   Healthy   ok

Investigate and resolve any unhealthy component statuses before attempting to delete the Namespace. For example, if the etcd component is unhealthy, you may need to troubleshoot and repair the etcd cluster.

For Kubernetes versions v1.19 and above, since componentstatuses is deprecated, you can use the following command:

kubectl get --raw='/readyz?verbose'

A healthy output should look like this:

[+]ping ok
[+]log ok
[+]etcd ok
[+]etcd-readiness ok
[+]informer-sync ok
[+]poststarthook/start-kube-apiserver-admission-initializer ok
[+]poststarthook/generic-apiserver-start-informers ok
[+]poststarthook/priority-and-fairness-config-consumer ok
[+]poststarthook/priority-and-fairness-filter ok
[+]poststarthook/storage-object-count-tracker-hook ok
[+]poststarthook/start-apiextensions-informers ok
[+]poststarthook/start-apiextensions-controllers ok
[+]poststarthook/crd-informer-synced ok
[+]poststarthook/bootstrap-controller ok
[+]poststarthook/rbac/bootstrap-roles ok
[+]poststarthook/scheduling/bootstrap-system-priority-classes ok
[+]poststarthook/priority-and-fairness-config-producer ok
[+]poststarthook/start-cluster-authentication-info-controller ok
[+]poststarthook/start-kube-apiserver-identity-lease-controller ok
[+]poststarthook/start-kube-apiserver-identity-lease-garbage-collector ok
[+]poststarthook/start-legacy-token-tracking-controller ok
[+]poststarthook/aggregator-reload-proxy-client-cert ok
[+]poststarthook/start-kube-aggregator-informers ok
[+]poststarthook/apiservice-registration-controller ok
[+]poststarthook/apiservice-status-available-controller ok
[+]poststarthook/kube-apiserver-autoregistration ok
[+]autoregister-completion ok
[+]poststarthook/apiservice-openapi-controller ok
[+]poststarthook/apiservice-openapiv3-controller ok
[+]shutdown ok
readyz check passed

  • Investigate and resolve any unhealthy component statuses before attempting to delete the Namespace. Each component might have unique troubleshooting steps depending on the issue. For example, if the etcd component is unhealthy, you may need to troubleshoot and repair the etcd cluster.

  • Ensure that the Kubernetes control plane components, such as the API server, controller manager, and scheduler, are running correctly. Verify that there are no error messages or issues in the logs of these components.

  • Check the health of the worker nodes in your cluster:

kubectl get nodes -o wide
NAME     STATUS   ROLES                  AGE   VERSION        INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                           KERNEL-VERSION                      CONTAINER-RUNTIME
ultron   Ready    control-plane,master   23d   v1.26.3+k3s1   172.17.66.235   <none>        Rancher Desktop WSL Distribution   5.15.90.1-microsoft-standard-WSL2   docker://20.10.21

Investigate and resolve any issues with nodes that are in a NotReady state or have other issues.

  • If all of the above yields nothing, verify that the kubelet service is running properly on each node by checking its logs and status.

By thoroughly examining the health and stability of your Kubernetes cluster, you can identify and resolve issues that might be causing a Namespace to become stuck in the Terminating state. Ensuring your cluster’s overall health will not only resolve Namespace deletion problems but also contribute to a smooth and efficient Kubernetes experience.

Cause 4: Custom Resource Definitions (CRDs) and Namespaces

Custom Resource Definitions (CRDs) can play a role in Namespaces being stuck in the Terminating state. CRDs extend the Kubernetes API by defining new resource types, which may affect the deletion process. To handle CRDs in the context of stuck Namespaces:

List all CRDs in your cluster:

kubectl get crds

Inspect the CRDs to determine if any are associated with the Namespace you are trying to delete.

Delete any associated CRD instances within the Namespace:

kubectl delete <custom_resource_name>.<api_group> -n <namespace_name>

If necessary, remove the CRD itself after deleting its instances:

kubectl delete crd <custom_resource_name>.<api_group>

Cause 5: Resource Quotas and Stuck Namespaces

Resource quotas can also impact Namespaces getting stuck in the Terminating state. Quotas limit the amount of resources that can be consumed within a Namespace, and exceeding these limits may cause issues.

Check the resource quotas for the Namespace:

kubectl get resourcequotas -n <namespace_name>

If the resource usage is exceeding the quota, you may need to adjust the quota or reduce resource consumption within the Namespace.

To update the resource quota, edit the ResourceQuota object:

kubectl edit resourcequota <resource_quota_name> -n <namespace_name>

Adjust the limits as needed, then save and exit the editor.

The Namespace Deletion Process

After identifying and addressing the potential cause(s) behind the stuck Namespace, proceed with the Namespace deletion process:

Eliminate all resources within the Namespace:

kubectl delete all --all -n <namespace_name>

Force Namespace deletion:

The kubectl delete namespace command offers additional parameters to help you tailor the deletion process to your specific requirements:

  • –grace-period: This parameter sets the duration in seconds that the system should wait before forcefully deleting the Namespace. By setting the grace period to 0 (–grace-period=0), you instruct Kubernetes to skip the waiting period and immediately proceed with the deletion.

  • –force: The –force parameter ensures that the Namespace is deleted forcefully, bypassing the default graceful deletion process. This can be helpful in cases where the Namespace is stuck in the Terminating state due to various issues discussed earlier.

kubectl delete namespace <namespace_name> --grace-period=0 --force

Reevaluate the Namespace status:

kubectl get namespaces

Regenerate the Namespace, if necessary:

kubectl create namespace <namespace_name>

By understanding and addressing these potential causes, senior engineers can effectively resolve a Namespace stuck in the Terminating state.

There you have it, these comprehensive strategies will enable you to enjoy a more efficient and smoother Kubernetes experience, ensuring optimal performance and reliability in their container orchestration system.