Introduction To Containers, Docker, and Kubernetes

By Derek Winchester

Computer applications are quickly becoming the lifeblood of the digital realm. These applications are used to make our daily jobs easier and more efficient and are very much considered a reliable aspect of running any successful business. As such, the business of application creation has been booming for quite some time. This highly lucrative sector has made a wide variety of app developers rich, while also making it possible for companies and professionals to boost their productivity and even save some money.

App developers are constantly creating applications which they must test, deploy, and perfect. This is where containers, Docker, and Kubernetes come into play. Each of these tools plays an intricate part in helping developers contain and deploy applications. Moreover, since many companies are shifting to a microservices-based architecture, the use of containers is considered a more congenial method of implementing their applications. That said, let's look at how each of these work, and how they have become the proverbial holy trinity of application development and deployment.

What are Containers?

Simply put, containers were created as a solution to a conundrum that made it next to impossible to get software to run reliably when being moved from its original computing environment. No matter if the application is being moved from a staging environment to production, or from the original developer's laptop to a testing environment, containers are there to keep the software safe and free from corruption. While applications are safe and efficient when used in the environments in which they were created, developers often encountered snags when they tried to venture outside of their original environments.

Containers consist of an entire runtime environment (which is an application, all its dependencies, libraries and binaries, and all the required configuration files). The containerization of these application platforms the various differences in OS distribution and other underlying infrastructure can be abstracted away. Containers are essentially the first line of defense in terms of protecting applications from being corrupted or destroyed when they are beyond deployed into other environments.

Before they created containers, deploying various applications simultaneously on the same virtual machine was a perilous move. This would often cause unpredictable things to happen, which could destroy the application, if not the system overall.

The creation of containers not only made it possible to separate and contain applications, and deploy them on the same machine simultaneously, but they also made it easier to quickly and easily deploy these newly created applications worldwide. For this reason, containers will soon be used as a more efficient replacement to the traditional VM.

What is Docker?

On the other hand, Docker is used for building and running containers. They are built using a Docker File. These files essentially define every aspect of the requirements for operating a Docker System. Using the Docker File, users can build a Docker Image, which is the static, portable component that fuels the Docker Engine.

Docker is the most popular platform for containers. Given that they were open source from the start, they quickly gained traction and popularity among a wide variety of users. In fact, approximately 30% of enterprises are now using Docker regularly.

Nevertheless, while Docker makes it easier to work with containers, they also present several issues. For instance, there was no way to coordinate and organize the various containers. Additionally, there was no easy method of upgrading the applications without interrupting the service. Also, there was no simple way to check the health of the various applications. This is where Kubernetes come into play.

What is Kubernetes?

Kubernetes is an open source management platform that helps to unify clusters of nodes into one functional system. While Docker was created to run on a single node, Kubernetes was created to run in clusters.

Despite the existence of Docker Swarm (which is a container orchestration tool that allows users to manage multiple containers that can be deployed across multiple platforms), Kubernetes has become an essential tool when working with Dockers, as it offers the following benefits:

?         Compute Scheduling: Kubernetes figures out the best resource needs for your containers and runs them automatically.

?         Manages Volume: It is also used to manage the level of storage being used by your various applications.

?         Horizontal Scaling: Kubernetes also uses CPU and custom metrics to add or remove instances as necessary.

?         Rollouts and Rollbacks: One very impressive feature of Kubernetes is that it takes the time to monitor the health of all new instances. Therefore, if a failure occurs, it is automatically rolled back to the previous version.

?         Self-Healing: Kubernetes automatically replaces crashed containers.

?         Configuration and Secrets: It can also manage application secrets and configurations.

To Make it Plain

Containers were created as a solution for the inability to use and deploy multiple applications on one system. Subsequently, Docker made it easier to manage these containers. Lastly, Kubernetes was created to make it simpler to manage both containers and Docker in a manner that is most practical and efficient.

Therefore, if you have an interest in any of these tools, you must, by default, have an interest in all of them. Although each of them has their own benefits and unique features, that all work best when they are used in conjunction with one another. Over the years, these tools have become a respected trifecta that serves as a solid foundation for the rapid development and deployment of applications of all kinds.