What are Kubernetes Annotations
The question of Annotations and the use of them in Kubernetes is often asked. We will present an elaborate description of the concept and origin of Kubernetes annotations in this article. The best way for us to describe Annotations would be to call them “metadata”. Metadata is, as we all know, data that defines and labels other data.
In Kubernetes, there are two possible ways to add metadata, one is through Kubernetes labels, the other is through Kubernetes annotations. There are no more similarities between them, except this. However, there are a few dissimilarities. Kubernetes labels allow the user to detect, choose, and work on Kubernetes objects, while Kubernetes annotations, as mentioned earlier, are simply non-detecting metadata that cannot perform the same functions.
Let’s see how Kubernetes Annotations allows the user to attach any non-identifying metadata to Kubernetes objects. An example could be the telephone number of a person who is in charge of the Kubernetes tool or object-related information needed to debug commitments. In other words, annotations can be used for storing information that can be beneficial and can also offer content and context to the DevOps teams.
What do you mean by Kubernetes Annotations?
An annotation describes a Kubernetes concept. It adds nameless metadata to the Kubernetes object list. This signifies that the picker doesn’t have the consent to enquire about the Kubernetes objects. When we say objects, we mean objects that have definite annotations attached to them. Simply put, annotations are a way of detecting and choosing the Kubernetes objects.
We all know that Kubernetes is an open-source platform, but the components that are present in Kubernetes don’t have the consent to use annotations to implement any operations to the Kubernetes cluster. Annotations can be of any form, they can be organized or unorganized and can be small or big. Kubernetes Annotations have one more proficiency that the Kubernetes labels lack.
Metadata, having characters can be added in Kubernetes annotations but not in Kubernetes labels. Moreover, annotations deliver data and evidence about the Kubernetes articles. This additional information can be useful as a tool or library material. Annotations can be very impactful to the users who are working on the Kubernetes cluster. It can be used as an interacting tool to communicate with all the Kubernetes objects as it has access to all information and also the ability to comprehend and work on those objects. Let’s say, for example, the user wants to add pager-related information about a person and also wants to attach some knowledge-based article.
Why are Kubernetes Annotations needed?
Till now we have talked about the origin and concept of annotation, now we will be focusing on the importance of annotations in Kubernetes. In the documentation for Kubernetes, annotations are recommended as the method of adding metadata externally to a cluster. The data and information regarding Kubernetes annotations can also be of any type. Adding random non-detecting metadata is always valuable as it helps the Application Programming Interface (API) server to store the information regarding the recovery of data by tools or libraries.
Kubernetes annotations, i.e., a pair of values, are attached to default definitions. Annotations serve many purposes. Prometheus is one type of monitoring server that is being used at present. The starter chart can be used to add a set of Prometheus annotations to the Kubernetes cluster. The start chart is available to the public and can be used for annotations in any way.
How does an Annotation Operate in Kubernetes?
The keys and value pairs of annotations fall under the same bracket as of Kubernetes labels. The value pairs can be divided into two sections, the first section is called a Prefix and the other section is called a Name. Though a prefix of a key is not mandatory, every annotation must have a name. The two sections of an annotation can be split using a slash ‘/‘. The name section can have a maximum of 63 characters and it must start and end with an alphanumeric character ([a-z, 0-9, A-Z].
The alphanumeric characters should also have a dash (-), or an underscore (_), or a dot (.), or an alphanumeric character itself between them. The prefix section, however, is not compulsory, but when you use it, you must put a DNS subdomain to it. The overall length of the prefix must be less than 253 characters and should also end with a slash (/).
Uses of Kubernetes Annotations
Kubernetes Annotations are very helpful and their uses are many. Some of the important uses of it are listed below for your reference:
- Annotations can be used to attach create, free, or to information related to the create number, free ID, address of the registry, hashes for an image, etc.
- It can be useful for debugging works as well by providing a name, version, and creating information related to the client library.
- During the origin of the Kubernetes object, an annotation can be helpful to add information related to the user and the system.
- Annotations are used to differentiate the various fields of Kubernetes that are controlled by the declarative configuration management from the default values assigned by the client.
- The phone number or pager number of a person can also be added with the help of annotations to discover if something related to the information occurs.
- Annotation helps to attach the link of knowledge-based articles for troubleshooting and to find any error or issues related to the Kubernetes objects.
- Lastly, annotations are used to attach a pointer for logging purposes, monitoring purposes, managing purposes, inquiring, or auditing.
Example of Kubernetes Annotation
The below example will help us to see the uses of namespaces, Pods, and services along with the insertion of Kubernetes Annotation.
- The default services of Kubernetes and the Kubernetes Pods are contained within the namespaces in the form of, Kube-system. Those services will inherit a few features like Application, Environment, and Location labels from the configuration and alignment segment of the Container Workload Profile. Kubelink Annotations are used to convey a part of the Illumio-system namespace to Kubernetes.
- Kubernetes annotations also describe the way a new application works. The application namespace is set and deployed with two different deployments of web and database applications. A part-by-part segmentation of the Web and Database applications requires several role labels. To deploy every configuration, a Role label must be added to the Kubernetes annotations.
- There is another pod in Kubernetes, which is known as “nginx”. Let’s say you want to add some annotations such as a pager number of a person, a URL, or a designation for an image repository, and you want to attach them to a knowledge-based article. All these mentioned features fall under the metadata primitive section of the Kubernetes annotations. ‘Kubectl’, another default annotation in Kubernetes, is used to check if we can add any type of annotations to the list of Kubernetes objects or not.
Conclusion
In this article, we have tried to present a brief guide about Kubernetes Annotations. In this article, we have briefly explained what Kubernetes Annotations are, and examined how to use them using examples. In addition to information related to Kubernetes, Kubernetes annotations provide random information that’s not related to Kubernetes itself.