Kubernetes is a portable, extensible, open-source platform for managing containerized applications and services that facilitates both declarative configuration and automation. Kubernetes provides a platform to configure, automate, and manage:
- Intelligent and balanced scheduling of containers
- Creation, deletion, and movement of containers
- Easy scaling of containers
- Monitoring and self-healing abilities
Challenges with Previous Technologies
Before Kubernetes there were containers, which became popular because they simplified going from application development to deployment without having to worry about portability or reproducibility. Developers can package an application and all its dependencies, libraries, and configuration files needed to execute the application into a container image. A container is a runnable instance of an image. Container images can be pulled from a registry and deployed anywhere the container runtime is installed: on your laptop, servers on-premises, or in the cloud.
Compared to virtual machines, containers have similar resources and isolation benefits, but are lighter in weight because they virtualize the operating system instead of the hardware. Containers are more portable and efficient, take up less space, use far fewer system resources, and can be spun up in seconds.
Managing containers for production is challenging. As the container market continued to grow and many workloads transitioned to fully production-grade containers, it was clear cluster admins needed something beyond a container engine. Key capabilities were missing, such as:
- Using multiple containers with shared resources
- Monitoring running containers
- Handling dead containers
- Moving containers so utilization improves
- Autoscaling container instances to handle load
- Making the container services easily accessible
- Connecting containers to a variety of external data sources
Advantages of Kubernetes
Containers paved the way to build cloud native systems, in which services are implemented using small clouds of containers. This created an enormous opportunity to add and adopt new services to make the use of containers easier, faster, and far more productive. Since it was open-sourced by Google in 2014, Kubernetes has become the de-facto standard for container orchestration. Kubernetes leverages the power of containers while simplifying the management of services and machines in a cluster.
A Pod is a logical grouping of one or more containers, which are scheduled together and share resources. Pods enable multiple containers to run on a host machine and share resources such as storage, networking, and container runtime information.
Kubernetes Clusters abstract their underlying computing resources, allowing users to deploy workloads to the entire cluster as opposed to a particular server. A Kubernetes cluster consists of at least one master node that manages the cluster and multiple worker nodes, where containerized applications run using Pods.
Kubernetes architecture enables:
- A single administrator to manage thousands of containers running simultaneously
- Workload portability and orchestration of containers across on-site deployments to public or private clouds and to hybrid deployments in between