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When Giants Clash: Kubernetes vs Docker Swarm

devgraph profile image DevGraph Originally published at blog.engineyard.com Updated on ・7 min read

By Ritu Chaturvedi

According to a 2020 report from DataDog, nearly 90% of containers are run using container orchestration tools. What’s more interesting is that in 2018, only 50% of Docker environments were orchestrated.

Container orchestration tools play a big part in the software development industry, and the need for a DevOps engineer that understands how to use them to manage running containers is rising fast.

The need for orchestration is clear. Orchestration platforms let you automate your container management, improving your efficiency and productivity, as well as your app’s scalability and availability among many other benefits.

Because of the rapid growth of the orchestration industry, there are a lot of options you can pick from. But the abundance of shiny new tools brought back a new problem: How do you know which platform suits you best?

Undoubtedly, Kubernetes and Docker are leaders of current containerization technology. Kubernetes is the most popular orchestration platform, and Docker is the most used containerization platform.

In this article, we’ll explore two of the most popular options for an orchestration platform: Docker Swarm, the native, and Kubernetes, the gold standard.

What’s the Difference?

Before we delve in to talk about which option is best for your application, let’s get to know each software separately so you have a clearer picture of the fundamental differences between the two of them.

Kubernetes

Kubernetes is an open-source orchestration platform created by Google and managed by the Cloud Native Computing Foundation (CNCF).

Usually used to manage complex platforms, Kubernetes has every feature you need from an orchestrator including monitoring, automated management, and load balancing.

The structure of a Kubernetes cluster is made up of master nodes, worker nodes, and pods.

Master node: This is where most of the work is done. Master nodes are the control plane that takes commands through the API server, decides how to reach the desired state, and instructs the worker nodes. The four components that make up a master node are:
○ API server acts as the front end of the system.
○ Scheduler monitors the system for new pods and assigns them to a node.
○ etcd is a consistent and highly-available key-value storage where Kubernetes stores all of its data.
○ Controller manager acts as the brain of the master node. It monitors the state of the cluster, compares it with the requested state, and makes adjustments to reach the desired condition.

Worker nodes: A virtual or physical machine responsible for communicating with the master node and carrying out the instructions of the master node.
Pods: A collection of one or more containers plus its shared resources.

Docker Swarm

Docker Swarm is the native clustering engine installed for Docker. As it’s made for and by Docker itself, it’s easy to use if you’re already using Docker Engine and in the Docker ecosystem. It’s easy to familiarize yourself with Swarm as the commands to it are similar to Docker’s.

The structure of a swarm, which is a cluster of virtual or physical Docker hosts working together in swarm mode, involves manager nodes, worker nodes, and tasks.

Manager nodes: Responsible for achieving or maintaining the desired state through orchestration and cluster management, as well as assigning tasks to worker nodes.
Worker nodes: Accept and run tasks from manager nodes and report back on the state of the tasks.
Tasks: Includes a container and the command needed to run the Docker containers.
Although it’s simpler than Kubernetes, Docker Swarm benefits from an excellent collaboration with Docker, as it’s the default cluster manager.

Let’s Compare

Installation

If you’re already using Docker to create containers, chances are you already have Docker Swarm installed on your machine.

Setting up a cluster is also easy and flexible, as you can easily deploy a node to a cluster as a manager or a worker, as well as promoting or demoting them any time you want.

On the other hand, Kubernetes uses a lot of components that you need to install and configure manually so you can use all of them together. While this creates a modular platform that may work well for some, it’s not an ideal setup if you’re looking for convenience.

There’s also a lot of planning involved when using Kubernetes. You need to know most of the cluster configurations beforehand, including how many nodes you’ll be using, IP addresses of the nodes, the role of each node, and other metrics.

Fortunately, most public cloud providers offer Kubernetes as their default orchestration platform, saving you a lot of time if you’re deploying your app to the cloud. However, if you’re interested in trying out a limited version of Kubernetes without much fuss, there’s a single-node Kubernetes installed with Docker for Desktop that you can use.

Load Balancing

Docker Swarm has a built-in load balancer. Containers in a single cluster join in on a single network so that connections can be established from any node to any container. Requests are distributed using the service name through a DNS. You can also use an external load balancer.

With Kubernetes, pods are defined as a service, which provides easy access from load balancers to other pods without worrying about IP addresses. Generally, an ingress is used for load balancing.

Container Setup

As it uses most of the same commands, the commands you’re going to use in Swarm are similar to the ones you most likely used in Docker.

It’s also compatible with most of the tools that are compatible with Docker. However, it also means the operational limits set to the Docker API are also set on Docker Swarm.

Instead of the Docker CLI, Kubernetes uses kubectl as its command line tool. This adds to the pile of things you need to learn before you can use Kubernetes smoothly and since you can’t use Docker Compose or Docker CLI to define containers. When switching platforms, you’ll need to rewrite your YAML definitions and commands.

Scalability

Compared to Kubernetes, Docker Swarm can deploy containers faster, leading to a faster reaction time to scale.

Kubernetes, on the flip side, deploys and scales slower than Docker Swarm. A unified set of APIs and strong guarantees about the cluster state may slow down the process.

Functionality

Docker Swarm provides simplistic features supported by additional third party features you can get through plugins. Docker Swarm also provides high availability through redundancy, quick and easy setup, and faster container deployment and scalability.

On the other hand, Kubernetes is much richer in features, especially automated ones that can minimize the time spent on managing deployment. Automation features offered by Kubernetes include self-healing capabilities, monitoring, and horizontal scaling. Although, it’s much harder to set up and slower to deploy compared to Docker Swarm.

Compatibility

Docker Swarm can be used as long as you can install Docker.

However, if you’re more attracted to the idea of deploying your containers on the cloud, Kubernetes is the best bet for you as it’s default orchestration engine in most popular cloud solutions.

Both are compatible with any operating systems both in the cloud and on-premises as long as it supports containerization technology.

Learning Curve

It’s much easier to get started with Docker Swarm, as most of the commands are already familiar.

Kubernetes, on the other hand, requires expertise to use. However, the time spent on learning how to use Kubernetes effectively will be well-spent thanks to the resource-effective features it offers

Pros and Cons of Kubernetes

Pros

• A full-featured orchestration platform for distributed systems.
• Time-saving, automated container management.
• Open-source and highly modular.

Cons

• Incompatible with current Docker CLI and Docker Compose.
• Hard to set up with a steep learning curve.
• Slower to deploy containers.

Pros and Cons of Docker Swarm

Pros

• Easy to set up and learn.
• Faster scalability.
• Integrates smoothly with Docker’s other features.

Cons

• Limited functionality to ones available on Docker API.
• Limited fault tolerance.
• Smaller community compared to Kubernetes.

When Should You Use Them?

Now that we’ve compared the two, let’s get back to our original question: Which one of these is suitable for you?

As one of the most popular orchestration platforms, Kubernetes is offered by most cloud providers as a built-in orchestration system. This makes Kubernetes your top choice if you’re already planning to run your application on the cloud.

You should also use Kubernetes if you don’t mind doing the heavy-lifting upfront, have a complex containerized application, and can benefit greatly from the features offered by Kubernetes.

On the other hand, Docker Swarm is the right platform for you if you need to get your app up and running quickly and easily. If you have a simpler system that won’t benefit much from Kubernetes, you’ll save yourself from a lot of pain by picking Docker Swarm.

In the End...

Docker Swarm and Kubernetes are both good options for a container orchestration platform to help you manage your microservices-based application. The deciding factor is the requirements you set on your application and its performance.

If you want something quick, easy, and simplistic, you should go with Docker Swarm. It also works very well with other Docker tools and you’ll have a smooth transition as it’s the native orchestration software.

On the other hand, Kubernetes is much more suited to a complex distributed system, thanks to its set of tools. It can also integrate seamlessly with the cloud and the chosen production environment of many applications.

Still looking for some more support? If you want to learn more about how to orchestrate your containers, contact our team today for state-of-the-art support and cutting-edge knowledge.

docker swarm, kubernetes, container orchestration


This blog Originally appeared on Engineyard.com

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