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Kubernetes vs. Docker Swarm: How These Container Orchestration Options Compare

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By: David Bisson

March 8, 2021

Organizations are using a growing number of containers in production. In a 2020 survey, the Cloud Native Computing Foundation (CNCF) found that the percentage of organizations running at least 250 containers had jumped up 28% to more than 50% for the first time. Meanwhile, the percentage of organizations running fewer than 250 containers and 50 containers dropped by 26% and 43%, respectively.

Organizations need to find a better way to manage so many containers at once. That explains why so many organizations are turning to container orchestration. The central argument here is scalability. As explained by TechBeacon, orchestration technology enables organizations to schedule containers across their lifecycles and use container clusters for designating usage. These features allow organizations' containers to scale with their business needs.

There's a growing number of solutions that seek to bring these benefits and more to organizations. Even so, most organizations are turning to two in particular: Kubernetes and Docker Swarm. This blog post will provide an overview of what each of these technologies entails. It will then look at them side by side to understand how they relate to one another and where they diverge. Finally, it'll end with a call to security for both.

What Is Kubernetes?

Kubernetes is an open-source platform that lets organizations manage containerized workloads and services using both declarative configuration and automation to minimize downtime. According to Kubernetes' documentation, organizations can use the platform to automatically mount public cloud providers, local storage, and other storage systems of their choice. They can also leverage Kubernetes to set the desired state for their deployed containers, have the platform move those containers to that desired state at a controlled rate, and replace or kill containers that don't respond to user-specified health checks.

What Is Docker Swarm?

Docker Swarm is a set of cluster management and orchestration features made available in Docker Engine 1.12. Its features rely on SwarmKit, a toolkit for orchestrating distributed systems. Organizations can group machines running SwarmKit into two types of nodes: manager nodes, which handle cluster management tasks, and worker nodes, Docker Engine instances which execute containers. Users leverage what is known as "services" to declare the desired state of a group of tasks. A manager node then accepts that service and schedules it in the swarm using one or more replica tasks. Per Docker's website, this type of model allows organizations to scale up or down by declaring the number of tasks they want to run for each service. Meanwhile, the cluster manager monitors the cluster state and reconciles differences between the baseline and the actual state.

Where Kubernetes and Docker Swarm Come Together

As gleaned from the above descriptions, both Kubernetes and Docker Swarm allow organizations to define the desired state and then monitor deployed containers against that state. That's not the only place where Kubernetes and Docker Swarm come together, however. Liquid Web identifies a couple more:

  • Both work with microservices. AWS notes that his software development model breaks down apps into small, independent services owned by self-contained teams. This approach makes applications both easier and faster to scale, develop and modify. Using Kubernetes or Docker Swarm, organizations can augment those microservices' workloads.

  • Both use clustering to improve load stability. The New Stack explains that Kubernetes distributes pods of containers among nodes, thereby offering availability if a pod fails. It's a similar case with Docker Swarm. Users can replicate services in Swarm nodes, allowing manager nodes to manage the overall cluster resources to ensure availability.

Some Areas Where the Two Go Apart

All of that said, there are certain areas where the two technologies stand apart from one another. These include the following:

  • Installation: Users need to manually install Kubernetes by downloading and installing kubetctl, the Kubernetes Command Line Interface (CLI). BMC recommends that users understand the platform and cloud computing to make sure that installation goes smoothly. By contrast, all users need to do with Docker Swarm is to install Docker Engine on a machine, assign IP addresses to hosts, and open protocols and ports between them. They can then assign their manager and worker nodes.

  • Logging and monitoring: Kubernetes comes with built-in tools for logging and monitoring, notes Hacker Noon, thus making it easy for users to understand the cause of failures and to stay abreast of the health of their environments. Docker Swarm doesn't come with built-in logging and monitoring tools; however, users can leverage ELK and Reimann along with other third-party tools to achieve this functionality.

  • Scalability: FAUN describes Kubernetes as "an all-in-one framework for distributed systems." It's complex in the sense that it offers a unified set of APIs and strong guarantees about the cluster state. These characteristics slow down the process of deploying a container, which makes scaling more difficult. The same isn't the case with Docker Swarm. Users can deploy containers and scale their environments quickly.

The Need for Security

Either Kubernetes or Docker Swarm can help organizations meet their container orchestration needs. Along the way, however, organizations might consider giving some thought to their deployed containers' security. StackRox explains why:

Although containers enable greater speed, portability, and the ability to take advantage of microservices architectures, they can also create security blind spots and increase your attack surface. As more containers are deployed, maintaining adequate visibility into your cloud-native infrastructure components becomes more difficult. The distributed nature of containerized applications makes it difficult to quickly investigate which containers might have vulnerabilities, maybe misconfigured, or pose the greatest risks to your organization.

With that said, organizations can learn how to secure their Kubernetes and Docker Swarm by clicking here and here, respectively.

About the Author: David Bisson is an information security writer and security junkie. He's a contributing editor to IBM's Security Intelligence and Tripwire's The State of Security Blog, and he's a contributing writer for Bora. He also regularly produces written content for Zix and several other companies in the digital security space.

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