Kubernetes Basic Concepts¶
Every cloud operator is itching to wrap their head around the basic concept of Kubernetes. If you're such a person, you would realize that even if you have tried to read a Kubernetes article recently, it is not uncommon for you to stumble upon words that will make your head spin.
When I read a Kubernetes article more than 40 months ago, contained in each paragraph of the article were strange words I hadn't seen in my life. So I clearly understand what you’re going through. Well, in this article, we are going to dive into those strange words related to Kubernetes because they are very important in unraveling the complexities involved in Kubernetes.
Let's get started.
Key Kubernetes Concepts You Should Know¶
Kubernetes API¶
API means application programming interface. With Kubernetes API, users can communicate with their cloud infrastructure. This serves as the front end of the control plane. After determining whether a request is authentic, the Kubernetes API server handles all basic operations.
Cluster Architecture¶
The Google Kubernetes Engine commonly called GKE is built on a cluster, and the Kubernetes instances that represent the containerized apps all run on top of that cluster. This cluster is what is most times referred to as Cluster Architecture.
A cluster architecture is made up of many worker machines, known as nodes, and at least one control plane. The Kubernetes cluster orchestration system is executed on these control planes and node devices.
Container¶
A container is a software technology that combines a program with all of its runtime components, particularly to facilitate the speedy and dependable running of the application in a range of scenarios. Dependability and scalability are achieved by running software as microservices, which is a common containerization method.
Containerized applications¶
These are applications that operate in an enclosed runtime environment known as containers. These applications and all of their dependencies, such as system libraries, binaries, and configuration files, are contained within containers.
Scheduler¶
The scheduler places containers following the most recent metrics and resource requirements. Additionally, the scheduler selects nodes for pods that don't already have one to run on after noting those pods. The master node controls the scheduler.
Deployment¶
A program that has been replicated is managed by an object known as a deployment, which makes sure that any instances that break down or become unresponsive are swiftly replaced. Deployments help to make sure that your application, in at least one instance, is prepared to respond to user requests.
Nodes¶
Workloads are completed by putting containers into pods that are hosted on Kubernetes nodes. A node is a machine that performs work. A node could be a virtual or physical computer depending on the cluster.
Every cluster typically consists of a large number of nodes, and each node has the kubelet, Kube-proxy, and container runtime. It is also important to note that there are two types of nodes contained in a cluster. They are master nodes and worker nodes.
Pods¶
The smallest unit in the Kubernetes ecosystem is a pod, which is a grouping of one or more containers operating at once on your cluster.
Controller Manager¶
To compare the cluster's present state to its desired state, the controller manager conducts controller procedures. The controllers that are managed include replication controllers, endpoint controllers, and node controllers. The master nodes are responsible for managing the controller.
Cluster Autoscaler¶
Based on metrics like node utilization and pending pods, the cluster autoscaler is in charge of adjusting the size of a Kubernetes cluster. Nodes are added to the cluster when the autoscale finds unscheduled pending pods as a result of resource constraints.
In addition, a node is removed from the autoscaler when its utilization falls below a specified threshold established by the cluster administrator.
Container Runtime¶
Application software that may operate containers on a host machine is known as a container runtime, commonly referred to as a container engine.
Workload¶
A Kubernetes-based application is referred to as a workload. On Kubernetes, you run your workload inside a collection of pods, whether it consists of a single component or several interconnected components. A pod in Kubernetes denotes a collection of active containers on your cluster. Pods in Kubernetes have a predetermined lifespan.
Kubernetes Operator¶
A Kubernetes operator is an implementation controller that enhances the capabilities of the Kubernetes API to set up, customize, and control instances of complicated applications at the behest of a Kubernetes user.
CRD¶
CRD which means custom resource definition is a powerful and effective function added to Kubernetes 1.7. The Kubernetes API is extended with a CRD, which offers a solution for storing and recovering structured data.
CNF¶
A network operation that would ordinarily be carried out by a physical device is called a Cloud-Native Network Function (CNF). It is implemented as software that runs inside a Linux container (often coordinated by Kubernetes).
GitOps¶
For cloud-native applications, GitOps is a method of performing Continuous Deployment by utilizing tools developers are already acquainted with, such as Git and Continuous Deployment tools, it concentrates on a programmer approach when managing infrastructure.
CI/CD¶
This means continuous integration and continuous delivery. Continuous integration and continuous delivery, also known as continuous deployment, are processes that are integrated into software engineering under the acronym CI/CD or CICD. By requiring automation in application development, testing, and deployment, CI/CD fills the gaps between development and operations teams and activities.
ChatOps¶
With ChatOps, tasks related to software design and deployment can be communicated about and carried out more easily via chat clients, chatbots, and real-time communication technologies. The principal channel for continuing communication in a ChatOps context is the chat client.
Chat Client¶
This is the program used to manage internet sites or instant messaging (IM) on the user's computer.
Kube-Proxy¶
Kube-proxy oversees the upkeep of network policies and controls node-to-node communication channels. It also makes sure that every node in a particular cluster is using the Kubernetes application model. The worker nodes manage the Kube proxy.
Kubelet¶
To guarantee that containers are running in a Pod, Kubelet communicates with the Docker engine, the most popular tool for creating and maintaining containers. Additionally, it accepts a set of PodSpecs and ensures that the containers that match them are fully functional. The worker nodes control the Kubelet.
Declarative¶
The true power of Kubernetes is shown by declarative management. You specify how the final result should appear, and Kubernetes handles the rest. In a declarative system, the user enters a representation of the desired state, which the system then reads to identify the commands needed to move the system from its current state to the desired state.
In addition to the term 'Declarative', declarative deployments give you the ability to specify how an app should be maintained, utilizing numerous techniques while allowing for pretty awesome flexible deployment process components.
Namespace¶
When numerous people or enterprises share a Kubernetes cluster, namespaces provide a means to divide clusters into virtual sub-clusters. A cluster can accommodate any number of namespaces, each of which can communicate with the others despite being logically isolated from the others.
ReplicaSet¶
A ReplicaSet is a program that continuously runs several replicas of a Pod while maintaining the predetermined number of Pods. Its goal is to keep the required number of Pod replicas operating in a cluster at all times to avoid users from having no access to their program if a Pod malfunction or is unavailable.
Conclusion¶
As a cloud operator who desires to adopt Kubernetes as an orchestration system, knowing what each concept related to Kubernetes is, is akin to knowing the functions of the various parts of your body as a human being. The knowledge of these concepts will help you easily understand the functions of Kubernetes.