Kubernetes vs. Docker Swarm: A Complete Comparison Guide

There are a countless number of debates, discussions and social clatter talking about Kubernetes and Docker. If you have not dived deep, you would think that both of the open-source technologies are in the fight of the container supremacy. Let’s make it clear that, Kubernetes and Docker Swarm are not rivals! Both have their own pros and cons and can be used depending on your application requirements.

In this article, more light is shed upon:-

• How have Kubernetes and Docker changed the era of software development?
• How has it revolutionized the way of DevOps consulting?
• Although they are different, how it can unify the processes of development and integration?
• What restrictions come to the scenario?

If you are looking to develop for modern cloud infrastructure or looking for DevOps implementation, then understanding of the full concept of Kubernetes and Docker is a must. This comprehensive article will take you on the journey of Kubernetes vs. Docker Swarm from scratch and will help you to answer to each of the important questions.

Let’s start with,

Container, Containerization and Container Orchestration– A Quick Intro

A container is the software package that contains an application’s code, configurations, and dependencies which delivers operational efficiency and productivity. Here, you can know exactly how it will run which means it is predictable, repeatable and immutable. The rise of containers has been a huge enabler for DevOps as Service and can overcome the largest hurdle of security faced today.

Containerization makes the applications portable by virtualizing at the operating-system level, creating isolated, encapsulated systems which are kernel based. Containerized apps can be dropped in anywhere and run without dependencies or requiring an entire VM, eliminating dependencies.

But, what if, when there are multiple containers?

Here container orchestration is needed!

Container orchestration is the process that can typically deploy multiple containers to implement an application through automation is called container orchestration. Platforms like Kubernetes and DockerSwarm are the container management and container orchestration engine that enable users to guide container deployment and automate updates, health monitoring, and failover procedures.

This all sounds really nice, but how to actually use tools and build container?

Let’s begin with Docker

Docker

“Build, Ship, and Run Any App Anywhere”

Docker is a container management service which helps developers to design application and make it easier to create, deploy and run applications by using containers. Docker has a built-in mechanism for clustering containers, called “swarm mode.” With swarm mode, you can use Docker Engine to launch application across multiple machines.

Docker Swarm – Tool to Manage Docker Container

Docker Swarm is Docker’s own native clustering solution for Docker containers which has an advantage of being tightly integrated into the ecosystem of Docker and uses its own API. It monitors the number of containers spread across clusters of servers and is the most convenient way to create clustered docker application without additional hardware. It provides you with a small-scale but useful orchestration system for the Dockerized app.

Pros of using Docker Swarm

• Runs at a faster pace: When you were using a virtual environment, you may have realized that it takes a long time and includes the tedious procedure of booting up and starting the application that you want to run. With Docker Swarm, this is no more a problem. Docker Swarm removes the need to boot up a full virtual machine and enables the app to run in a virtual and software-defined environment quickly and helps in DevOps implementation.

• Documentation provides every bit of information: The Docker team stands out when it comes to documentation! Docker is rapidly evolving and has received great applause for the entire platform. When version gets released at a short interval of time, some platform doesn’t maintain/take care to maintain documentation. But docker swarm never compromises with it. If in case the information only applies to the certain versions of a docker swarm, the documentation makes sure that all information is updated.
• Provides simple and fast configuration: One of the key benefits of Docker Swarm is that, it simplifies the matter. Docker Swarm enables the user to take their own configuration, put it into a code and deploy it without any hassle. As Docker Swarm can be used in various environments, requirements are just not bound by the environment of the application.
• Ensures that application is isolated: Docker Swarm takes care that each container is isolated from the other containers and has its own resources. Various containers can be deployed for running the separate application in different stacks. Apart from this, Docker Swarm cleans app removal as each application runs on its own container. If the application is no longer required, you can delete its container. It won’t leave any temporary or configuration files on your host OS.
• Version control and component reuse – With Docker Swarm, you can track consecutive versions of a container, examine differences or roll-back to the preceding versions. Containers reuse the components from the preceding layers which makes them noticeably lightweight.

Cons of using Docker Swarm

• Docker is platform dependent: Docker Swarm is a Linux agonistic platform. Although Docker supports Windows and Mac OS X, it utilizes virtual machines to run on a non-Linux platform. An application which is designed to run in docker container on Windows can’t run on Linux and vice versa.
• Doesn’t provide storage option: Docker Swarm doesn’t provide a hassle-free way to connect containers to storage and this is one of the major disadvantages. Its data volumes require a lot of improvising on the host and manual configurations.  If you’re expecting Docker Swarm to solve the storage issues, it may get done but not in an efficient and user-friendly way.
• Poor monitoring: Docker Swarm provides the basic information about the container and if you are looking for the basic monitoring solution than Stats command is suffice. If you are looking for the advanced monitoring than Docker Swarm is never an option. Although there are third-party tools available like CAdvisor which offers more monitoring. It is not feasible to collect more data about containers in real-time with Docker itself

To Avoid These Shortfalls, Kubernetes Can be Used

Automated Container Deployment, Scaling and Management Platform

When an application is developed with the diverse components across numerous containers on several machines, there is a need for the tool to manage and orchestrate the containers. This is only feasible with the help of Kubernetes.

Kubernetes is an open source system for managing containerized application in a clustered environment. Using Kubernetes in a right way helps the DevOps as a Service team to automatically scale up-down the application and update with the zero downtime.

Pros of using Kubernetes

• Its fast: When it comes to continuously deploy new features without downtime; Kubernetes is a perfect choice. The goal of the Kubernetes is to update an application with a constant uptime. Its speed is measured through a number of features you can ship per hour while maintaining an available service.
• Adheres to the principals of immutable infrastructure: In a traditional way, if anything goes wrong with multiple updates, you don’t have any record of how many updates you deployed and at which point error occurred. In immutable infrastructure, if you wish to update any application, you need to build container image with a new tag and deploy it, killing the old container with old image version. In this way, you will have a record and get an insight of what you did and in-case if there is any error; you can easily rollback to the previous image.
• Provides declarative configuration: User can know in what state the system should be to avoid errors. Source control, unit tests etc. which are traditional tools can’t be used with imperative configurations but can be used with declarative configurations.
• Deploy and update software at scale: Scaling is easy due to its immutable, declarative nature of Kubernetes. Kubernetes offers several useful features for scaling purpose:
  • Horizontal Infrastructure Scaling: Operations are done at the individual server level to apply horizontal scaling. Latest servers can be added or detached effortlessly.
  • Auto-scaling: Based on the usage of CPU resources or other application-metrics, you can change the number of containers that are running
  • Manual scaling: You can manually scale the number of running containers through a command or the interface
  • Replication controller: The Replication controller makes sure that cluster has a specified number of equivalent pods in a running condition. If in-case, there are too many pods; replication controller can remove extra pods or vice-versa.

• Handles the availability of the application: Kubernetes checks the health of nodes and containers as well as provides self-healing and auto-replacement if in-case pod crashes due to an error. Moreover, it distributes the load across multiple pods to balance the resources quickly during accidental traffic.

• Storage Volume: In Kubernetes, data is shared across the containers, but if pods get killed volume is automatically removed. Moreover, data is stored remotely, if the pod is moved to another node, the data will remain until it is deleted by the user.

Cons of using Kubernetes

• Initial process takes time: When a new process is created, you have to wait for the app to commence before it is available to the users. If you are migrating to Kubernetes, modifications in the code base need to be done to make a start process more efficient so that users don’t have a bad experience.
• Migrating to stateless requires many efforts: If your application is clustered or stateless, extra pods will not get configured and will have to rework on the configurations within your applications.
• The installation process is tedious: It is difficult to set up Kubernetes on your cluster if you are not using any cloud provider like Azure, Google or Amazon.

Kubernetes vs  Docker Swarm: A Quick Summary