Introduction
Kubernetes, often referred to as K8s, is an open-source platform that manages Docker containers in the form of a cluster. It is a system for running and coordinating containerised applications across a cluster of machines. Kubernetes is a production-ready, open-source platform designed with Google’s accumulated experience in container orchestration, combined with best-of-breed ideas from the community.
What is Kubernetes?
Kubernetes is a portable, extensible, open-source platform for managing containerised workloads and services. It facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.
What can Kubernetes do for you?
With modern web services, users expect applications to be available 24/7, and developers expect to deploy new versions of those applications several times a day. Containerisation helps package software to serve these goals, enabling applications to be released and updated without downtime. Kubernetes helps you make sure those containerised applications run where and when you want, and helps them find the resources and tools they need to work.
Key Components of Kubernetes
Control Plane - The control plane’s components make global decisions about the cluster, such as scheduling, and detecting and responding to cluster events. It includes:
API Server is the front end for the Kubernetes control plane that exposes the Kubernetes API.
ETCD Database is a consistent and highly-available key-value store used as Kubernetes backing store for all cluster data.
Scheduler watches for newly created Pods with no assigned node, and selects a node for them to run on.
Controller Manager runs controller processes.
Worker Nodes - These are the machines that run containerised applications. Every cluster has at least one worker node. It includes:
Kubelet is an essential component of Kubernetes that runs on each node in the cluster. It’s often referred to as the "node agent". Here are some of its key responsibilities:
Pod Execution
Resource Management
Health Monitoring
Node Registration
Kube Proxy is a network proxy which plays a crucial role in the networking of Kubernetes and is responsible for implementing a virtual IP mechanism for Services. It supports two backends for Layer 3/4 load balancing iptables and IPVS. Here are some of its main responsibilities:
Service to Pod mapping - it maintains a network routing table that links the IP addresses of Service pods with the respective addresses of the Service. This ensures that requests sent to a service are accurately routed to the relevant pods.
Continuous Re-Mapping - it continually updates the network routing table to account for changes in the cluster, such as pod termination and recreation. This ensures the accuracy and currency of the Service-to-Pod mapping.
Load Balancing - it facilitates pod-to-pod traffic balancing, ensuring that requests are evenly distributed across multiple application instances.
Container runtime engine - Executes the containers.
Kubernetes Cluster - The basic unit of deployment and is a set of node machines for running containerised applications. If you’re running Kubernetes, you’re running a cluster. The cluster is the heart of Kubernetes key advantage is the ability to schedule and run containers across a group of machines, be they physical or virtual, on premises or in the cloud. Kubernetes containers aren’t tied to individual machines. Rather, they’re abstracted across the cluster. This allows for applications to be more easily developed, moved, and managed
Pods - The smallest deployable unit of application unit. Here are some key characteristics and functionalities of Pods:
Group of Containers - A Pod is a group of one or more containers, such as Docker containers, with shared storage and network resources. The containers in a Pod are always co-located (run on the same physical or virtual machine) and co-scheduled (started and stopped together).
Shared Context - The contents of a Pod run in a shared context, which is a set of Linux namespaces, cgroups, and potentially other facets of isolation. This shared context is the same thing that isolates a Docker container.
Ephemeral Nature - Pods are ephemeral by nature. If a Pod (or the node it executes on) fails, Kubernetes can automatically create a new replica of that Pod to continue operations.
Workload Management - Pods in a Kubernetes cluster are used in two main ways:
Pods that run a single container. In this case, you can think of a Pod as a wrapper around a single container.
Pods that run multiple containers that need to work together. These co-located containers form a single cohesive unit.
Kubectl - A command-line tool for interacting with the cluster. It is a command-line tool that enables communication between the Kubernetes API and the control plane. It’s often referred to as the “Kubernetes CLI version of a Swiss army knife” due to its versatility. Here are some of its key functionalities:
Declarative Resource Management - kubectl allows you to declaratively manage Kubernetes workloads using resource configuration. This is the preferred approach for managing resources.
Imperative Resource Management - It also supports commands to manage Kubernetes workloads using command-line arguments and flags. This is typically used for development.
Printing Workload State - kubectl can print information about workloads, which is useful for debugging.
Interacting with Containers - It supports commands for interacting with containers, such as exec, attach, cp, logs.
Cluster Management - kubectl supports commands to drain workloads from a node so that it can be decommissioned or debugged.
Benefits of Using Kubernetes
Automated deployment and management - Kubernetes automates the deployment, scaling, and containerising of the application. It reduces the errors that can be made by humans, making the deployment more effective.
Scalability - You can scale the application containers depending on the incoming traffic. Kubernetes offers Horizontal pod scaling, the pods will be scaled automatically depending on the load.
High availability - You can achieve high availability for your application with the help of Kubernetes. It also reduces latency issues for the end users.
Cost-effectiveness - Kubernetes helps you reduce resource utilisation and control the over provisioning of infrastructure.
Improved developer productivity - Developers can concentrate more on the developing part. Kubernetes reduces the efforts of deploying the application.
Conclusion
Kubernetes is a powerful tool for managing containerised applications. It provides a robust, scalable, and efficient platform for deploying, scaling, and managing applications in a distributed environment. Whether you’re a developer looking to streamline your deployment process or an operations professional looking for a scalable solution for managing containers, Kubernetes offers a comprehensive and flexible feature set that can meet a wide range of needs.