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December 14th, 2020

How to Create Your own Kubernetes Custom Resources


Kubernetes has the reputation of being highly modular in terms of managing containerized services. Even the controllers and the resources on the Kubernetes platform have the capability of being customized, which adds to the modularity of the platform.

Custom Resources can be used to extend the Kubernetes API to allow the addition of newer, more specific features to your resources cluster. Though there are many other ways to add new users to your Kubernetes platform, using Customer Resources is the preferred method for many.

The Reasons Which Make Custom Resources Invaluable

You can think of many reasons which make Custom Resources a vital tool to have. The primary reason is the compatibility that they have with Kubectl. The “get resources” command using Kubectl can be executed from the platform with ease. Custom Resources are pretty easy to create too.

The native Command Line Interface on the Kubernetes platform also allows the use of Custom Resources. Updating the Custom Resources is also easy with the use of commands. Plus, they are great to have where there is a need to automate the update and maintenance process.

Custom Resources are more flexible than ConfigMaps. This is mainly because the Custom Resources can be run as a Native object instead of other objects.

The Process of Creating A Custom Resource

Custom Resources can be created pretty quickly. We will now have a brief look at the process of Custom Resource creation.

The process starts with creating a CustomResourceDefinition, which is stored in a YAML file. A YAML file shows you the API in use, the type of resource that you add (which would be CustomResourceDefinition in your case), and the CRD metadata. The command that is used to achieve the result mentioned above is the “Kubectl Apply.”

Now you can start working on the process of creating your objects. The APIVersion- type-metadata and specifications combination used by default is the same for the objects which are about to be integrated. The default specifications make the creation of Custom Resources easy. A person with any level of experience can create and use Custom Resources.

CRD isn’t the only method of adding Custom Resources. The API aggregation method allows greater command over your API behaviors. Custom Resources Definition does not give you additional features like switching the protocol buffers on, going beyond CRUDs with logs or exec, and allowing the endpoints to assist the PATCH HTTP verbs.

API Aggregation approach does involve a bit of programming. However, you can access the aggregation layer by using the API Aggression technique. The EnableAggregatedDiscoveryTimeout=false method can be used to completely remove the timeout restrictions.

The Commands and Features That can be Made Accessible

Custom Resources can be integrated into the Kubernetes platform with ease and in a very short time. Whatever method of creation you choose, the Custom Resources allow you to use specific features that can make the Resources functional.

  • CRUD allows the basic functions of CRUD through HTTP or Kubectl. It is an important feature that allows you a bunch of other options along with Custom Resources.
  • Watch is a very useful feature that allows you to monitor the changes on an object or the user-specified deployment.
  • Admission Webhooks are used to run the validation tests that can help in the reduction of CRUD runtimes.
  • Labels and Annotations are used to keep your cluster well-organized. They can also be used for maintenance.
  • The generation of Client Libraries and access to the tools that help in the Client Library Generation

The list does not end here. There are numerous possibilities, as there are no restrictions on adding objects and creating new objects.

The one thing to note here is that a few features can be accessed only through the API Aggregator. The Aggregation Layer will juxtapose the Custom Resources to make the Kube-API server recognize the newer objects. The API Aggregation allows a flexible approach to customizing your data storage, like API versioning, among other features.

You would not be able to use the custom storage during the deployment of the CRDs but is available during the use of the API Aggregation method. Custom Storage can also allow the use of additional security features.

Protocol Buffers are also accessible through the API Aggregator. It allows extra commands like LOG and EXEC. They might not always be needed. So, CRDs are better in cases that don’t require these features.

Deployment of Custom Resources

Before deploying your new Custom Resources to the platform, you would have to check a few things first.

  • All third-party packages and installation bundles should be present before adding the custom resources. This will allow the deployment of the resource without any errors.
  • The standard RBAC roles won’t be enough for you to run the Custom Resources. Therefore, always ensure the roles that the CRDs and the APIs are sufficient in the execution.
  • You will be able to use the Custom Resource from the Kubectl, along with clients on the Kubernetes platform.
  • APIs would require new deployment, while the use of CRD makes the deployment and maintenance easier

Kubernetes has allowed the deployment and maintenance of the Custom Resources on the go. Updating Custom resources is crucial to the user. The use of CRD makes deployment and maintenance easier. These factors determine the use of Custom Resources over a longer period of time.


The native Kubernetes resources can also be transformed into Custom Resources. This shows how modular the Kubernetes platform can be. Custom Resources can be created with ease and are extremely helpful. Adding newer features to your cluster can be helpful in the long run. So, go ahead and give it a try.

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