Kubernetes components

“Kubernetes” derived its name from a Greek word meaning pilot or helmsman. It is a widely recognized open source platform that is portable and extensible for managing workloads and services that are containerized. It facilitates both automation and declarative configuration. Auto scaling, Load balancing, Self-healing, Lifecycle management, persistent storage, devsecops support, and others are a few features of Kubernetes. Since it is designed by Google and also has better functionality as compared to its competitors, it remains to be a market leader. To maintain the containers, the use of Kubernetes is the need of the hour for every business. Now, let us explore each of the concepts in detail!

Kubernetes components - Table of Content

Components of Kubernetes

The control plane components of Kubernetes help in making a global decision with regards to the cluster, and also detect and respond to the cluster events. For instance, Scheduling or beginning a new pod especially when a field is unsatisfied during a deployment. The components in a cluster can run on any machine. Following is the list of components and a brief about them.

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Kube-apiserver:

As the name implies the Kube apiserver, is a component of Kubernetes (control panel) which exposes the Kubernetes Application Programming Interface. It is the front end of the control plane in Kubernetes. It refers to the main implementation of the API Server of Kubernetes. It is designed so that it scales horizontally, i.e., when more instances are deployed. The user can run many instances of Kube apiserver, and then balance between those instances. Therefore it is a central touch point that can be accessed by any user, components, and automation in the cluster of Kubernetes. 

Etcd:

It is a highly available and consistent key value store that is used in Kubernetes as backing the store for all the available cluster data. Since Kubernetes is a system that is distributed, it requires etcd which can store data.  It manages many of the distributed database problems such as networking and race conditions to help Kubernetes. The user should make sure that if etcd is used as a backup store, a backup plan for those data is a must. 

Kube Scheduler:

This component in Kubernetes is responsible for watching pods that are newly created and have no assigned nod. It helps to select a node to run on them.  Factors such as policy/hardware/software/constraints, Collective or individual resources requirements, data locality, deadlines, anti-affinity specifications, and others are taken into account in scheduling the decisions.

Kube Controller manager: 

It refers to the component that helps in running the processes. Ideally, each controller is a unique process but to reduce complexity, it is combined in a single binary to run in one process. Few of these controllers are 

  • Node controller - It is responsible to notice and respond when a node goes down.
  • Service Account and Token controllers - It is responsible for creating default accounts and tokens for API access for new namespaces.
  • Endpoints controller - It helps in populating the pods and joint services.

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Cloud controller manager:

It is the component that helps in embedding control logic that is cloud specific. The cluster can be linked to the cloud provider’s API and also helps in separating components that interact with the cloud platform that only interacts with the cluster from the components. The manager only runs those controllers specific to the cloud provider. Node controller, Service controller, and rote controller are the controllers that have cloud provider dependencies. The cloud controller manager uses a plugin mechanism that permits various cloud providers the facility of integrating their platforms with Kubernetes. The user can run Kubernetes with the use of a cloud controller manager on private, public, and also hybrid clouds. 

Node Components

A machine that helps to run Kubernetes workload is called Node. A node can host multiple pods. The components of the node run on every single node. This helps to maintain the running pods and provides a runtime environment for Kubernetes. Following are the components of Node:

Kubelet:

Kublet refers to an agent in the cluster that runs on every node. The main objective of it is to make sure that all the containers are running in a Pod. The various mechanisms provide Podspecs, a set of which is taken into account by Kubelet, to ensure the Podspecs described in the container are healthy and running.  It is not responsible to manage those containers that Kubernetes didn’t create. It is also termed a primary agent. 

Kube-proxy:

It refers to the network proxy in the cluster that runs on each node. It assists to implement a part of the service concept of Kubernetes. It also ensures that the rules on the nodes are maintained. These rules facilitate communication of the network from inside or outside of the cluster. It makes use of the operating system as a packet filter layer if one is available, or else it forwards itself the traffic.

Container runtime:

It is the software that helps in running the containers. It is responsible for pulling various images from both the public and private registers and then running containers based on the images. The most popular among users is Docker. 

Addons

Kubernetes resources such as DaemonSet and Deployment are used by Addons to implement all the cluster features. As these provide cluster-level features, the Kube system namespace contains namespaced resources for addons. Over several years Kubernetes' popularity has risen, as it provides the user with an easy way to support, manage and scale the applications. Many tools can be easily integrated with Kubernetes to improve the effectiveness and function of the Kubernetes clusters and containers. Below are some of the addons and a brief about them.

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DNS:

DNS stands for Domain Name System. Having a cluster DNS is a must since many examples rely on it. While having other addons is not mandatory.  Cluster DNS refers to a DNS server, along with the other DNS servers in the environment that serves DNS ( Domain Name System) records for Kubernetes services. The containers which are started by Kubernetes will automatically include the DNS server in DNS searches of theirs. 

Web UI (Dashboard):

Dashboard is a web-based UI (User Interface) in the Kubernetes cluster which is of general purpose. The users can manage the cluster and also troubleshoot applications that are running in it. In a nutshell, the user will be able to manage the whole cluster.

Container Resource Monitoring:

The addons are used to record in the central database the containers in general time-series metrics. It also provides a User Interface to browse the data. It has now become a popular method of deploying the applications and bringing other benefits. For instance, Improve the operation and portability of the application.

Cluster-Level Logging: 

The mechanism of cluster-level logging is used for saving the container logs in a central log store with a search and browsing interface. It requires a separate backend for analysing, storing, and also querying logs. The user can integrate with many logging solutions in Kubernetes as it does not have a storage solution to log the data. 

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Kubernetes Architecture

Kubernetes Architecture is popularly known as Kubernetes application deployment or client server architecture. It is used for scaling, composing, deploying, and also managing the container of the application of the host clusters. Therefore it is considered an open source platform for deployment and management of the containers. 

Kubernetes Architecture
Conclusion

Hope the article has helped you to understand the concept of Kubernetes along with its components and architecture. Thus to sum up Kubernetes which is also known as K8s is ideally a system that is open source to manage containerized applications spread across multiple hosts. As per a survey, 95% of the users of Kubernetes find clear benefits in using it, along with optimum utilisation of resources and a shorter software development cycle. Do comment in the section below for any queries.

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Srivalli
Srivalli
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As a senior technical content writer for HRK tainings, srivalli patchava has a greater understanding of today's data-driven environment, which includes key aspects of data management and IT organizations. She manages the task of creating great content in the areas of software testing, DevOps, Robotic process automation. Connects with her on Linkedin and Twitter.

Master components refer to the components that are created and managed independently without the need for any application. API server, etcd, Scheduler, and Controller manager are a few of the master components of Kubernetes.

Kubernetes contains eight key objects and they are Pods, Replica set, Services, Volumes, Name spaces, stateful sets, config maps and secrets, and daemon sets.

The total number of nodes required for the Kubernetes cluster varies from one organisation to another. However, it is suggested to have a dozen nodes and two master nodes in a Kubernetes cluster.

Controllers in Kubernetes refer to the component which is responsible for regulating the cluster’s state and also performing the task.