The development and success of open source application container technologies – particularly Docker and Kubernetes – are having a transformational effect on application development across today’s software-centric organisations. Key to their success is the inherent flexibility and efficiency they add to the process of developing software applications.
Among their many benefits, application containers are not only lightweight but offer extremely rapid provisioning, often in the order of milliseconds. They also provide an alternative to the widely used Virtual Machine technologies that can consume a large amount of system resources and can suffer from a slow boot time.
In addition, containers allow organisations to build and operate infrastructure on a massive scale by maximising the number of applications running on a minimum volume of servers. This doesn’t just help meet the needs of today’s agile and fast growth businesses, but on a practical level delivers high performance to multiple users in a timely and efficient manner, even as demand fluctuates across different parts of an application.
The impact of all these advantages is that the adoption of Kubernetes, for instance, has soared. According to data published at the end of last year, its use among development teams grew from 27% in 2018 to 48% in 2020. Given the technology is less than a decade old, its adoption remains in the early stages of growth, with its use set to increase further across a wide variety of organisations and use cases.
Docker vs Kubernetes
Containers are portable and lightweight alternatives to Virtual Machines, and Docker is a containerization platform that has become the most popular technology of its kind in the world. Used on its own, however, it is not enough for managing containerized applications.
Kubernetes, a name which originates from the Greek for pilot or helmsman (or “‘k8s’ for short) is an open source platform that automates container operations. It Is one of the fastest growing container technologies and is frequently used alongside Docker to address the challenges associated with container management and orchestration.
Developers value Kubernetes because it significantly improves their ability to configure, deploy, manage and monitor their containerized applications – at any scale. What’s more, it helps manage container and application lifecycles alongside common administrative priorities, including high availability and load balancing.
Five Key Kubernetes Components
To better understand how Kubernetes works, it’s useful to take a look at five of its key components, beginning with nodes:
- Nodes
Kubernetes helps to manage clusters easily and efficiently across groups of hosts (which can be dedicated servers or virtual machines) that run the Kubernetes ‘master node’ (the control plane) and the Kubernetes worker nodes (the workers that run the containers). This now also includes Windows-based worker nodes that run Windows containers as well as Linux-based worker nodes that run Linux containers.
A Kubernetes node is typically a host with either master or worker node functionality. The master node runs processes such as the Kubernetes APIs (i.e., for kubectl, the native command-line interface for Kubernetes), while worker nodes run the application containers, including the container runtime.
- Pods
A Kubernetes pod is one or more containers running together, each of which has its own IP addresses and a domain name for when there is a set of pods.
- Services
A Kubernetes service is a way to expose an application that is running on a set of pods as a network service. Pods come and go, and therefore sometimes have a short lifespan. Services help the other pods find out and keep track of which pod IP address they should connect to.
- Operators
Operators function as clients of the Kubernetes API, control custom resources and enable automation of tasks such as deployments, backups and upgrades by watching events without editing Kubernetes code. The key attribute of an operator is the active, ongoing management of the application and includes failover, backups, upgrades, and autoscaling. Operators offer self-managing experience with knowledge baked in from the experts.
- Secrets
And finally, a Kubernetes secret is a Kubernetes object that stores sensitive information, such as an OAuth token or SSH key. This ensures that the information is only accessible when necessary.
For organisations adopting Kubernetes to run on their cloud infrastructure, some service providers offer self-installing nodes on either bare metal dedicated servers or virtual machines. The installation of a Kubernetes cluster is made easier by using deployment tools like kubeadm, while the Kubernetes.io website offers information covering both management best practices, among many other resources.
