When comparing Kubernetes vs Docker Swarm, the Slant community recommends Docker Swarm for most people. In the question“What are the best Docker orchestration tools?” Docker Swarm is ranked 1st while Kubernetes is ranked 2nd. The most important reason people chose Docker Swarm is:
This also means that containers can be launched with a simple `docker run` command and Swarm will take care of the rest, such as selecting the appropriate host on which to run the container.
Ranked in these QuestionsQuestion Ranking
Pro Open Source
Kubernetes is free and open source.
Pro Built on several years of experience with containers
Kubernetes was built on top of several years of experience from Google working on containers in production. It's a little opinionated on how containers should work and behave, but if used correctly it can help you achieve fault-tolerant systems.
Pro Fault tolerant
Almost everything in Kubernetes is designed to handle if parts of it fail or if your service crashed for whatever reason. So it's particularly adapted if you've a cluster (even a very small one).
Pro Works well with modern operating systems
Kubernetes works very well with modern environments (such as CoreOS or Red Hat Atomc) which offer lightweight computing nodes that you don't have to manage, since they are managed for you.
Pro Supported on several PaaS
Kubernetes is currently supported by Google Compute Engine, Rackspace, Microsoft Azure, and vSphere. Work is being done to support Kubernetes on OpenShift and CloudFoundry.
Pro Easy to do grouping tasks
Kubernetes uses labels which are key-value pairs that are attached to objects, usually pods. They are used to specify the characteristics of an object like the version, tier, etc. Labels are used to identify objects or groups of objects according to different characteristics that they may have, for example they can be used to identify all the pods that are included in the backend tier.
Through labels it's easier to do grouping tasks for pods or containers, like moving pods to different groups or assigning them to load-balanced groups.
Pro Great starting point for beginners
Kubernetes great for beginners who are just starting to work on clustering. It's probably the quickest and easiest way to start experimenting and learning cluster oriented development.
Pro Easy setup
This also means that containers can be launched with a simple
docker run command and Swarm will take care of the rest, such as selecting the appropriate host on which to run the container.
Pro Communicates with other Docker tools easily
Since Docker Swarm is a native Docker tool, it exposes the Docker API, making it possible t integrate it and communicate with other Docker tools (CLI, Compose, Krane, etc.).
Docker Swarm is much more lightweight than alternatives: Kubernetes and Mesosphere. Kubernetes, for instance, is very complex - it downloads and installs half of the web, where Docker Swarm has much, much smaller footprint.
Pro Open source
Docker Swarm is open source and provides great guides/documentation for those who want to contribute.
Pro Compatible with Docker Compose
This gives you a well-rounded workflow.
Con Cannot define containers through the Docker CLI
Kubernetes was not written for docker clustering alone. It uses a different API, configuration and different YAML definitions. So you can't use the Docker CLI or Docker Compose to define your containers. Everything has to be done from scratch.
Con Windows restrictions
Windows compatibility rules, the host OS version must match the container base image OS version. Only Windows containers with Windows Server 2019 are supported. Also other restrictions are present.
Con If used on an existing system, some re-organizing may be needed
Because of how opinionated Kubernetes is, it may be necessary to change some things if you decide to use Kubernetes as an orchestration tool in an existing application.
Con Sometimes Pods refuse to (re)start automatically
It happens that a Pod needs a manual kick before it runs properly, especially if you're near full utilisation of your machine resources. Sometimes it is just a long delay.
Con If a node dies in the Swarm Cluster, the containers on that node WILL be started on a another node ...
Con Not fault tolerant
If a node dies in your cluster, the containers on that node won't be restarted
Con Bounded by the limitations of the Docker API
If the Docker API doesn't support something, then you are pretty much out of luck when it comes to Docker Swarm, because it won't be supported by Swarm either.