Choose your Docker Management Tool: Kubernetes or Swarm
By Jack M. Germain
Docker container technology has been one of the most significant boons to functionality in the cloud. If you are not yet using container strategies, you probably will be soon; one way or the other.
Moving into the technology is a two-step process. First, you must adopt the concept of containers. Then you need an orchestration tool to schedule and manage your containers. Which one you choose is largely a matter of preference and need.
Docker is an advanced technology that brings users numerous computing benefits. This primer is a basic overview of a complex computer process. It presents the basics in a simple, straightforward way.
Docker is a software platform for containers. Containers package all the coding marvels needed for a computing task — or series of tasks — to run in an isolated environment. In short, a container provides the platform for a software package to run without a full operating system to support it.
That simple description makes containers sound like glorified virtual machines. But that would not be accurate. A VM can deploy several services that run different computing processes on the same computer. And while this general explanation is virtually the same for containers, the difference between them is how both technologies deploy.
For instance, one of the essential differences between the two methods is the bare metal that runs them. VMs need a host computer and must share its resources. VMs run on a hypervisor platform that serves as the management tool. Consequently, not all computers can support virtual replication.
That support depends on the type of processor powering the computer. That limitation is significant. Running numerous VM sessions on the same computer or server is limited by the richness of the host machine’s resources.
Virtual Machines depend on an installed operating system to run. Containers, on the other hand, need just parts of an operating system to function. This means containers can run more efficiently and consume fewer system resources, giving them more functionality and better computing impact over VMs.
Another significant difference with containers is that while VMs can also run applications in isolation, the containers suffer the loss of functioning independently. Since containers lack an operating system or a hypervisor, they need their own management system.
Two popular, open-source technologies currently compete for this controlling element to Docker containers. Docker developed Swarm and now builds it into the Docker Toolbox. The more mature container manager is Google’s Kubernetes. Each solves the problem of lost independent functioning by providing a system that works across multiple hosts, data centers, and different clouds.
The choice is yours. Docker functions well regardless of which management tool you use. The first step in deciding which tool is best for your operation is to understand how they differ.
The Kubernetes Engine
Kubernetes is an open-source system for automating deployment, scaling, and management of containerized applications. A Kubernetes cluster contains a collection of essential parts. Here’s a quick overview of these:
- Kubernetes deploys and schedules containers in groups of pods that typically include from one to five containers that collaborate to provide a service.
- Kubernetes has a flat default network model. It permits all pods to talk to each other by having containers in the same pod share an IP to communicate using ports on the localhost address.
- Kubernetes uses Labels to search and update multiple objects as if they were a single set.
- Kubernetes uses services as endpoints. These are connected to pods using label selectors.
- Kubernetes sets up a DNS server for the cluster to watch for new services and addresses them by name.
- Kubernetes uses replication controllers to instantiate pods. As a mechanism for improving fault tolerance, these controllers manage and monitor the number of running pods for a service.
The Swarm Factor
Docker’s developers now package Docker Machine, Compose, and Swarm into the Docker Toolbox. You can configure this troika of tools to work together to set up, manage, and cluster your containers.
Docker Swarm, now in beta release, is a clustering tool for Docker. It forms a swarm cluster using one or more Docker hosts. Swarm is designed to pack containers onto a host, so it can save other host resources for bigger containers. This clustering produces an advantageous economy of scale compared to randomly scheduling a container to a host in the cluster.
These are Swarm’s key factors that differentiate it from Kubernetes:
- Swarm has native clustering capabilities to turn a group of Docker engines into a single, virtual Docker Engine.
- A swarm contains only two components: agents and managers.
- One cluster has a host that runs a Swarm agent. Another host runs a Swarm manager.
- This is essential to the operation because the manager segment orchestrates and schedules containers on the hosts.
- Swarm uses a discovery service to find and add new hosts to the cluster.
- Swarm provides the standard Docker API. This furnishes an out-of-the-box performance that permits all the existing Docker management tools — including third-party products — to automatically and transparently scale over multiple hosts.
Subtle Differences between Swarm and Kubernetes
Both approaches — Kubernetes and Swarm — handle the same types of workloads as cloud-native applications. However, one big difference is how the technology handles scaling.
With Kubernetes, each application tier is defined as a pod. A deployment or replication controller handles scaling either manually or via automation. With Swarm, scaling individual containers is defined in the Compose file.
Other differences play out in how the manager systems handle high availability, load balancing, rolling application upgrades/rollbacks, logging and monitoring, storage, networking, service discovery, and performance and scalability.
Docker’s Bottom Line
Both Kubernetes and Swarm are tools that build virtual containers at scale. They offer two different means to getting to the same end. They operate differently and offer functionality that lets you better adjust to your specific needs.
Do not just use the Docker Swarm solution because it comes pre-packaged in the Docker Toolkit. First, let your IT team members get hands-on familiarity with both management tools. Let the IT team recommend which approach is easier to configure and deploy based on your company’s operation.
In the simplest of comparisons, selecting Kubernetes or Swarm is like picking your favorite Linux desktop after narrowing down all the options to two. How it serves your purpose is the deciding factor.
Please feel free to share below any comments, questions or insights about your experience with containers, Docker, Swarm or Kubernetes. And if you found this blog useful, consider sharing it through social media.
About the blogger: Jack M. Germain is a veteran IT journalist whose outstanding IT work can be found regularly in ECT New Network’s LinuxInsider, and other outlets like TechNewsDirectory. Jack’s reporting has spanned four decades and his breadth of It experience is unmatched. And while his views and reports are solely his and don’t necessarily reflect those of Linode, we are grateful for his contributions. He can be followed on Google+.
