Comparing Kubernetes and Docker Swarm

on Aug 7, 2017

For teams building and deploying containerized applications using Docker, selecting the right orchestration engine can be a challenge.  The decision affects not only deployment and management, but how applications are architected as well.  DevOps teams need to think about details like how data is persisted, how containerized services communicate with one another, load balancing, service discovery, packaging and more.  It turns out that the choice of orchestration engine is critical to all these areas.

While Rancher has the nice property that it can support multiple orchestration engines concurrently, choosing the right solution is still important.  Rather than attempting to boil the ocean by looking at many orchestrators, we chose to look at two likely to be on the short list for most organizations – Kubernetes and Docker Swarm.

Evolving at a rapid clip

To say these frameworks are evolving quickly is an understatement.  In the just the past year there have been four major releases of Docker (1.12, 1.13, 17.03 and 17.06) with dozens of new features and a wholesale change to the Swarm architecture.  Kubernetes has been evolving at an even more frenetic pace.  Since Kubernetes 1.3 was introduced in July of 2016 there have been four additional major releases and no less than a dozen minor releases. Kubernetes is at version 1.7.2 at the time of this writing with 1.8.0 now in alpha 2.   Check out the Kubernetes changelog to get a sense of the pace of development.

Comparing Kubernetes and Docker Swarm is a little like trying to compare two Rocket ships speeding along on separate trajectories.  By the time you catch up with one and get close enough to see what’s happening, the other is in a whole different place! 

Points of comparison

Despite the challenges posed by their rapid evolution, we decided to take a crack at comparing Swarm and Kubernetes in some detail, taking a fresh look at new capabilities in each solution.  At a high-level the two solutions do broadly similar things, but they differ substantially in their implementation.  We took both solutions out for a test drive (using Rancher running in AWS), got into the weeds, and compared them systematically in these areas:

  • Architecture
  • User experience
  • Ease-of-use
  • Networking model
  • Storage management
  • Scheduling
  • Service discovery
  • Load balancing
  • Healthchecks
  • Scalability

Lots for DevOps teams to ponder

Both Swarm and Kubernetes are impressive, capable solutions.  Depending on their needs, organizations could reasonably choose either solution.  If you are new to one solution or the other, understanding the strengths and weaknesses of different solutions, and differences in how they are implemented, can help you make a more informed decision.

Swarm is impressive for its simplicity and seamless integration with Docker.  For those experienced with Docker, evolving to use Swarm is simple.  Swarm’s new DAB format for multi-host, multi-service applications extends naturally from docker-compose, and the Swarm command set is now part of Docker Engine, so administrators face a minimal learning curve.

Customers considering larger, more complex deployments will want to look at Kubernetes.  Docker users will need to invest a little more time to get familiar with Kubernetes, but even if you don’t use all the features out of the gate, the features are there for good reason.  Kubernetes has its own discrete command set, API and an architecture that is discrete from Docker.  For Kubernetes, the watchword is flexibility.   Kubernetes is extensible and configurable and can be deployed in a variety of ways.  It introduces concepts like Pods, Replica Sets and Stateful Sets not found in Swarm along with features like autoscaling.   While Kubernetes is a little more complex to learn and master, for users with more sophisticated requirements, Kubernetes has the potential to simplify management by reducing the need for ongoing manual interventions.

About the whitepaper

Our comparison was done using Rancher’s container management framework to deploy separate environments for Docker Swarm and Kubernetes.  Rather than focus on Rancher however, comparisons are made at the level of Swarm and Kubernetes themselves.  Whether you are using Rancher or a different container management framework, the observations should still be useful.

Included in the paper are:

  • Detailed comparisons between Kubernetes and Swarm
  • Considerations when deploying both orchestrators in Rancher
  • Considerations for application designers
  • High-level guidance on what orchestrator to consider when

Download the free whitepaper for an up to date look at Kubernetes and Docker Swarm.

As always, we appreciate your thoughts and feedback!

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