It is like if you know the basics of Kubernetes, you would for sure be knowing that it is an open-source container orchestration platform designed for running the distributed applications and services at its scale. But this is also a fact that you may not understand its components and also how they are getting interacted.
Let us now proceed further and take a brief look at the design and its principles that are underpinned with Kubernetes. This is then proceeding further to explore how the different components of the Kubernetes work together.
Principles of Kubernetes:
The entire process of the Kubernetes cluster is based on three basic principles. Some details are being explained in the Kubernetes implementation details.
A Kubernetes cluster should be:
- Secure: The process would be followed by the latest security best-practices.
- Easy to use: With the simple commands it should be operable.
- Extendable: It shouldn’t favor one provider and should be customizable from a configuration file.
Components of Kubernetes Cluster?
The working Kubernetes deployment is called a cluster. It is that the visualization of Kubernetes clusters and that too in two parts. One is the control plane and the other is compute machine or nodes. With the owing of the Linux environment each node has its importance and it could be either in the form of a physical machine or virtual machine. Each node runs pods, which are made up of containers.
Now let us proceed further and have a look at some of the happenings in the plane of Kubernetes.
Control plane
Let us begin from its base and it is with the nerve center of the Kubernetes cluster. Here what we are talking about is the control plane. The clusters here are controlled with the help of Kubernetes components and that is being found in it. Also, along with the data, the details of the clusters state and its configuration is set up. Here these core Kubernetes can handle all the major important work and making sure that the containers are running adequately and also with the dedicated sources and resources.
The only plane that is having contact with the computing machine is the “control plane”. The configuration of the cluster is done in a certain way so its running process becomes easier and convenient. Indeed control panel makes sure that it does so.
Kube-API server
Thinking to interact with the Kubernetes cluster? Well, that the very first thing that needs to be done is the Kubernetes API that is kept in front of the Kubernetes control plane and lane. It is there easy to handle both internal and external requests. It is the API server that determines whether the request is valid or not. If it is valid then proceed further, and if not then hold the process right there. These APIs can be accessed through various methods and they are with REST calls, through the kubectl command-line interface, or other command-line tools such as kubeadm.
Kube-scheduler
Have you ever asked this question to yourself and that is worth value? The question is, Is your cluster healthy? There is one common concern that does arises which states that if there is a need for new containers, where will they fit? and that too in the Kubernetes scheduler.
The scheduler considers the resource needs of a pod, such as CPU or memory, along with the health of the cluster. Then it schedules the pod to an appropriate compute node.
Kube-controller-manager
Controllers the word itself communicates everything. It is the process that takes care of the actual running cluster. Also, it is the Kubernetes controller-manager that contains several controller functions and that too all in one. One controller consults the scheduler and makes sure the correct number of pods is running. If any of the pods go incorrect or wrong, it is another controller that notices it and responds to the error with immediate effect. A controller connects services to pods, so requests go to the right endpoints. And there are controllers for creating accounts and API access tokens.
etcd
A key-value store database where the configuration data and information is been kept and it is the state of the cluster is being lived in etcd. Fault-tolerant and distributed, etcd is designed to be the ultimate source of truth about your cluster.
What happens in Kubernetes Nodes?
Let us, mover, further, and have a look at some of the details that share the information which reveals what happens to these Kubernetes Nodes. So, here is the answer to all such questions and that is very well being mentioned below.
Nodes
It is a Kubernetes cluster that demands at least one compute node. But the fact is that they have many in general. The scheduling and the orchestrated pods are already running on the nodes. This then needs to be scaled up with the capacity of the cluster and also with many other nodes too.
Pods
The smallest and the simplest unit that is available in the Kubernetes object model is a Pod. It represents a single instance of an application. Each pod is made up of a container or a series of tightly coupled containers, along with options that govern how the containers are run. Pods can be connected to persistent storage to run stateful applications.
Container runtime engine
This is a fact that to run the containers, there is a need for each computes node that has a container in which there is a runtime engine. One of the examples here is Docker. But since it is Kubernetes, and we all know that it supports all other open containers with initiative compliant runtime as well as with rkt and CRI-O.
Kubelet
Each compute node contains a kubelet, a tiny application that communicates with the control plane. The kublet makes sure containers are running in a pod. When the control plane needs something to happen in a node, the kubelet executes the action.
Kube-proxy
Every single compute node contains Kube-proxy. It is a network proxy that is facilitating Kubernetes networking services. The Kube-proxy handles network communications inside or outside of your cluster—relying either on your operating system’s packet filtering layer or forwarding the traffic itself.
What is that other thing that Kubernetes Cluster would be requiring?
Again this is also one of the common questions that do arise in the mind. It is that after having all the needed data and information what else will the Kubernetes cluster requiring. Well, for this question too we have an answer to it and for the same do read and check it mentioned below.
Persistent storage
It is that beyond just managing the containers that are running in an application, Kubernetes can manage the application data that is being attached to a cluster. Kubernetes allows users to request storage resources without having to know the details of the underlying storage infrastructure. Persistent volumes are specific to a cluster, rather than a pod, and thus can outlive the life of a pod.
Container registry
It is in a container registry that the images are relying on the Kubernetes. This can be a registry you configure or a third party registry.
Underlying infrastructure
It is entirely up to you as to where and how to run Kubernetes. This can be either in any of the forms such as bare metal servers, virtual machines, public cloud providers, private clouds, and hybrid cloud environments. One of Kubernetes’s key advantages is it works on many different kinds of infrastructure.
Nobody said this would be easy
This simplified overview of Kubernetes architecture just scratches the surface. As you consider how these components communicate with each other—and with external resources and infrastructure—you can appreciate the challenges of configuring and securing a Kubernetes cluster.
Kubernetes offers the tools to orchestrate a large and complex containerized application. This is that it is very much related to (CI/CD) tooling, application services, storage, and most other components. There’s also the work of managing roles, access control, multitenancy, and secure default settings. Additionally, you can choose to run Kubernetes on your own or work with a vendor who can provide a supported version.
This freedom of choice is part of the flexible nature of Kubernetes. While it can be complex to implement, Kubernetes gives you tremendous power to run containerized applications on your terms and to react to changes in your organization with agility.
Kubernetes Controllers Overview
Here comes a small overview of the entire service. It is at the core of Kubernetes, that it has a very large set of controllers. It is the responsibility of the controller to make sure that the specific resources are used and this is at the desired state which is dictated by a declared definition. It is that the resources deviates from the desired state, and where the controller is being triggered to make sure that the necessary actions are taken state back to the place where it should be.
But, it is like the question arising that how do the controllers “know” that the changes are happening. To say in a precise manner, let us check us with an example to it. For example: When you scale up a deployment, it relates to sending a request to the API server with the new desired configuration. The API server in return publishes the change to all its event subscribers (any component that listens for changes in the API server). It does not instruct the controller or any event listener about how they should act. The implementation is left to the controller.
Conclusion:
On reading this article, it is very much updated that what the service is all about and how it works out. Cloud Stack Group is the leading and active builders of open-source container that provides and deals with all major types of AWS services, DevOps services, Kubernetes Services, Chef Servers, and other essential tools that are required for securing and simplifying the data. This also is the process, which automatically updates the container infrastructure.
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