What is Kubernetes and why use it | Container Orchestration is today’s topic. Introduction to Docker, the container ecosystem has been evolved significantly. Kubernetes is the open source container orchestration tool designed to automate deploying, scaling, and operating containerized applications.
Kubernetes is the portable, extensible open-source platform for managing the containerized workloads and services, that facilitates both declarative configuration and automation.
It has a vast, rapidly growing ecosystem.
Kubernetes support, services, and tools are widely available. Before we deep dive, let’s define the containers first.
What is Container
A Container is the collection of software processes unified by one namespace with access to the operating system kernel that it shares with the other containers and some to no access to different containers.
You create your Docker image and push it to a registry before referring to it in a Kubernetes pod.
Kubernetes doesn’t replace the Docker but it augments it.
However, Kubernetes does replace some of the top-level technologies that have emerged around Docker.
A runtime instance of the docker image contains the following three things.
- A Docker Image
- An execution environment
- The standard set of instructions
Core elements of Docker System
Docker ecosystem has the following two core elements.
- Docker Engine
- Docker Store
The Docker Engine comprised of the runtime and packaging tools.
It must be installed on the hosts that run the Docker.
Docker store is an online cloud service where user can store and share their images. It is also known as Docker Hub.
Difference between Container and Virtual Machine
Virtual Machine contains one or more applications that include the necessary binaries and libraries.
Virtual Machine(VM) contains the entire guest operating system to interact with the applications.
On the other hand, containers include the application and all of its dependencies and share the kernel with other containers.
The container does not tie to any infrastructure. It only needs a Docker engine installed on a Host.
The container runs isolated processes in the user space on the host OS.
Advantages of Containers
The container applications are portable.
The container applications are packaged in a standard way.
The deployment is easy and repeatable. DevOps engineers like them because it is straightforward to manage on different hosts.
Automated testing, packaging, and integrations can be automated more naturally.
The containers support the newer microservice architectures.
It removes the platform compatibility issues.
The DevOps team can isolate and debug the issues at a container level.
What is Container Orchestration
Container orchestration is the process of deploying containers on the computer cluster consisting of multiple nodes. The containerization approach is to package the different services that constitute an application into separate compute containers and to deploy those containers across a cluster of physical or virtual machines.
Container orchestration is the process that automates a deployment, management, scaling, networking, and the availability of container-based applications.
Containers support the VM(Virtual Machine)-like separation of concerns but with a far less overhead and far greater flexibility. As an output, containers have reshaped the way people think about developing, maintaining, and deploying the software. In the containerized architecture, the different services that constitute the application are packaged into the separate containers and deployed across the cluster of physical or virtual machines. But it gives rise to the need for the container orchestration: A tool that automates a deployment, management, scaling, networking, and availability of the container-based applications.
What is Kubernetes
Kubernetes is an open source platform designed to automate deploying, scaling, and operating application containers. The main goal of Kubernetes is to foster an ecosystem of components and tools that relieve the burden of running applications in the public and private cloud.
Kubernetes platform started at Google. It’s a successor to—though not a direct descendant of Google Borg project.
Kubernetes is the platform to schedule and run containers on the clusters of virtual machines. It runs on the bare metal, virtual machines, private data center, and public cloud.
Kubernetes is a container platform. You can use it with Docker containers to develop and build applications, and then use Kubernetes to run these applications on your infrastructure.
You are not bound only to use Docker containers. You can use other containers as well.
Kubernetes is the open source project that enables the software teams of all sizes, from the small startup to the Fortune 500 company, to automate deploying, scaling, and managing the applications on a group or cluster of server machines.
Kubernetes is the distributed system. It introduces its own orchestration space. Therefore, understanding its architecture is crucial.
Kubernetes “clusters” are composed of term called “nodes.”
The term “cluster” means “nodes” in the aggregate.
“Cluster” refers to an entire running system.
A “node” is the worker machine within the Kubernetes, (previously known as “minion”). The “node” may be a VM or a physical machine.
Each node has the software configured to run containers managed by the Kubernetes’ control plane.
The control plane is a set of APIs and software (such as
kubectl) that Kubernetes users interact with.
A control plane services run on the master nodes.
Clusters may have multiple masters for the high availability scenarios.
What can Kubernetes Do
Kubernetes’ features provide everything we need to deploy the containerized applications. Here are some key points.
- Container Deployments and Rollout Control. Describe all of our containers and how many we want with a “Deployment.” Kubernetes will keep track these containers running and handle the deploying changes such as the updating an image or changing environment variables with the “rollout.” You can pause, resume, and rollback changes as you wish.
- Resource Bin Packing. You can declare minimum, and maximum compute resources (CPU and Memory) for all the containers. Kubernetes will slot our containers into where ever they find fit. It increases our computational efficiency and ultimately reducing the costs.
- Built-in Service Discovery and Autoscaling. Kubernetes can automatically expose our containers to the internet or other containers in the cluster. It automatically load-balances traffic across the matching containers. Kubernetes supports the service discovery via environment variables and DNS, out of the box. You can also configure CPU-based autoscaling for the containers for increased resource utilization.
- Heterogeneous Clusters. Kubernetes runs anywhere. You can build your Kubernetes cluster for the mix of virtual machines (VMs) running the cloud, on-premises, or a bare metal in your datacenter. Choose your composition according to the requirements.
- Persistent Storage. Kubernetes includes the support for persistent storage connected to the stateless application containers. There is a support for Amazon Web Services EBS, Google Cloud Platform persistent disks, and many, many more cloud services.
- High Availability Features. Kubernetes is a planet scale. It requires special attention to high availability features such as a multi-master or cluster federation. Cluster federation allows us to link clusters together so that if one cluster goes down, the containers can automatically move to the other cluster.
These key features make Kubernetes well suited for running the different application architectures from the monolithic web applications, to a highly distributed microservice applications, and even batch driven applications.
Kubernetes containers are grouped into the “pods.” Pods may include one or more containers. All the containers in the pod run on a same node.
The “pod” is the lowest building block in the Kubernetes architecture. More complex abstractions come on top of “pods.”
“Services” define networking rules for exposing the pods to the other pods or exposing the pods to a public internet.
Kubernetes uses the “deployments” to manage the deploy configuration changes to the running pods and horizontal scaling.
A “deployment” is the template for creating the pods. “Deployments” are scaled horizontally by creating more “replica” pods from a template.
Changes to a “deployment” template trigger the rollout. Kubernetes uses rolling deploys to apply the changes to all running pods in the deployment.
Kubernetes provides the two ways to interact with a control plane.
The primary way is kubectl command to do anything with Kubernetes.
The second way is to use web UI with basic functionality.
Let’s see some of the more common terms to help you understand Kubernetes.
Master: The machine that controls the Kubernetes nodes. This is where all the task assignments originate.
Node: These machines perform the requested and assigned tasks. The Kubernetes master controls the nodes.
Pod: A group of one or more containers deployed to the single node. All the containers in the pod share an IP address, IPC, hostname, and other resources. Pods abstract the network and storage away from an underlying container. It lets you move the containers around the cluster more easily.
Replication controller: It controls how many identical copies of a pod should be running somewhere on the cluster.
Service: It decouples the work definitions from the pods. Kubernetes service proxies automatically get service requests to the right pod no matter where it moves to in the cluster or even if it’s been replaced.
Kubelet: The Kubelet service runs on nodes and reads the container manifests and ensures the defined containers are started and running.
kubectl: The kubectl is the command line configuration tool for Kubernetes.
The highest-level Kubernetes abstraction, the cluster, refers to a group of machines running Kubernetes (itself the clustered application) and the containers managed by it.
A Kubernetes cluster must have the master, the system that commands and controls all the other Kubernetes machines in a cluster.
Kubernetes nodes and pods
Each cluster contains the Kubernetes nodes. Nodes might be physical machines or VMs. Again, the idea is abstraction: Whatever an app is running on, Kubernetes handles the deployment on that substrate.
Kubernetes even makes it possible to ensure that specific containers run only on VMs or only on bare metal. Nodes run pods, the most basic Kubernetes objects that can be created or managed. Each pod represents the single instance of the application or running process in the Kubernetes and consists of one or more containers.
Kubernetes starts, stops, and replicates all the containers in the pod as a group. Pods keep the user’s attention on an application, rather than on the containers themselves.
Why do you use Kubernetes
Real production apps span into the multiple containers. Those containers must be deployed across the multiple server hosts.
Security for containers is multilayered and can be complicated. That’s where the Kubernetes can help.
Kubernetes gives us the orchestration and management capabilities required to deploy the containers at scale or these workloads.
Kubernetes orchestration allows us to build the application services that span over multiple containers, schedule those containers across the cluster, scale those containers, and manage the health of these containers over time. With Kubernetes you can take the real steps towards better IT security.
Kubernetes also needs to integrate with the networking, storage, security, telemetry, and other services to provide the comprehensive container infrastructure.
Kubernetes can also work with any container system that conforms to the Open Container Initiative (OCI) standards for container image formats and runtimes.
Conclusively, What is Kubernetes and why use it | Container Orchestration Explained article is over.