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Docker Swarm Vs. Kubernetes – The Subtle Differences

Written by Marius Rimkus
on April 14, 2020

Containers help developers ensure consistency across all platforms – from the initial development stages to the production process. Compared to traditional virtualization, they enable greater control, making them a popular choice for developers.

Kubernetes and Docker Swarms are essential tools used to deploy containers inside a cluster. They’re niche-specific and have cemented their places in the Docker container ecosystem.

Though both differ in how they achieve their goals, Kubernetes and Docker Swarm aren’t adversaries to each other.  Each has its pros and cons and can be used in different ways, depending on your application requirements.

If you’re a developer looking into container orchestration, it’s time to understand the intricacies of both containerization platforms.

 

Kubernetes

Kubernetes is an open-source system that automates deployment as it scales and manages containerized applications. The orchestrator is based on Google’s experience with working on Linux containers and was released in 2014.

Essentially, Kubernetes was designed to simplify the scalability of workloads that were using containers. By grouping containers into logical units, Kubernetes relieves the burden of running applications on public and private clouds.

Known to be highly complicated in the past, Kubernetes gradually saw updates that have made it more user-friendly. It allows users to outline parameters for applications to run within and define their interactions with other applications.

Kubernetes consists of the following components:

  • Pods: a group of containers on the same node created, scheduled, and deployed together
  • Labels: key-value tags assigned to identify elements like pods and replication controllers
  • Services: used to give names to Pod groups, which then act as load balancers, directing traffic to run containers
  • Replication Controllers: frameworks that are specially designed to ensure pod replicas are scheduled and running at any given moment

 

Docker Swarm

Docker Swarm is Docker’s native clustering agent – it uses standard Docker API and networking to simplify integration into preexisting Docker containers. Swarm turns a pool of Docker hosts into a single host.

It’s especially useful for developers to find their way around an orchestrated environment and for those that have more than one cloud environment to run this on.

In the beginning, Docker Swarm didn’t offer much in terms of container automation. With updates, however, container orchestration is now built into its core along with first-party support.

Docker Swarm core design focuses on four fundamental principles: simple yet powerful with a “just works” user experience, resilient zero single-point-of-failure architecture, default security with automatically generated certificates, and backward compatibility with existing components.

Docker Swarm consists of the following components:

  • Manager Nodes: includes Control Orchestration, Task Distribution, and Cluster Management
  • Worker Nodes: includes running containers and services that are assigned by the manager node
  • Services: a description of the blueprint through which individual containers can spread themselves across the nodes
  • Tasks: slots in which the containers place their work

 

Overview

Docker Swarm and Kubernetes both limit hardware usage to save resources. While both orchestration tools offer the same functionality, the particulars of their operation call for a closer examination:   

Kubernetes

Pros:

  • Open source and modular
  • Optimal functionality across multiple operating systems
  • Pods offer easy service organization
  • The strong foundation backed by professional experience

Cons:

  • Difficult to install and configure
  • Incompatibility with preexisting Docker CLI and Compose tools

Docker Swarm

Pros:

  • Quick, easy setup
  • Integrates well into existing Docker tools
  • Lightweight installation
  • Open-source

Cons:

  • Functionality is limited depending on what is available in the Docker API
  • Limited fault tolerance

 

Docker Swarm vs. Kubernetes – What Are The Differences?

Here are several ways in which Docker Swarm and Kubernetes differ:

Application Definition

Kubernetes deploys applications using a combination of pods, deployments, and micro-services. On the other hand, Docker Swarm deploys applications as services in a Swarm cluster. In this case, YAML is used to specify a multi-container.

Installation And Setup

With Kubernetes, the installation has to be done manually and needs careful deliberation before it can be run. Moreover, instructions differ from depending on the operating system and the provider. Kubernetes also need cluster configuration details like a node’s IP address well in advance.

In contrast, Docker Swarm is easier to install: only one set of tools is required for developers to understand how to build on the configuration. Consequently, Docker Swarm allows for additional flexibility – new nodes can join existing clusters as managers or workers.

Working On Two Systems

Developers will require forehand knowledge on CLI (Command Line Interface) to run Kubernetes on top of Docker. You will also need Docker CLI and supplemental Kubernetes common language infrastructure to navigate within structures and run programs.

Since Docker Swarm is inherently Docker tool, developers can use the same common language to navigate within structures. Additionally, the tool allows for higher speed and variability, making Docker considerably user-friendly.

Logging And Monitoring

Kubernetes supports various logging and monitoring tools when services are deployed within a cluster:

 

  • ElasticSearch, Logstash, Kibana.
  • Heapster/Grafana/ Influx – to monitor in the container

On the other hand, Docker Swarm supports monitoring only through third-party apps. Developers prefer to use Docker with Reimann for said purpose. Consequently, since Docker Swarm has an open API, users can connect multiple apps smoothly.

Scalability

Quite frankly, Kubernetes is an all-in-one framework for distributed systems. From there, its complexity further increases – it offers a unified set of APIs and strong guarantees on the cluster state. This slows down its ability to deploy and scale containers.

In comparison, Docker Swarm deploys containers faster and allows for quick reaction times that can scale on demand.    

High Availability

All pods in Kubernetes are distributed among nodes: this supports high availability by tolerating application failure. Moreover, load balancing services can detect unhealthy pods and effectively remove this, which further strengthens high availability.

In Docker Swarm, the Swarm manager is responsible for the whole cluster and manages the worker nodes’ resources. As such, Docker Swarm also offers high availability. Developers can replicate services in Swarm nodes.

Networking

The Kubernetes network is flat, enabling effective communication within all pods. It requires two CIDRs – the first responsible for ensuring all pods receive an IP address and the other for services.   

In Docker Swarm, nodes joining a cluster create an overlay network of services spanning across all hosts in the Swarm. Users can encrypt container data traffic when creating an overlay network.

 

Conclusion

Docker Swarm offers a fast solution that is easy to get started with. On the other hand, Kubernetes caters to the demand for greater complexity.

As such, Docker is a favorite among developers that prioritize simplicity and fast deployments. Similarly, high profile internet companies prefer Kubernetes for their compatibility with production environments.

That being said, Kubernetes is superior to Docker Swarm on a wide range of technical aspects, and cloud providers are opting to switch over to Kubernetes managed services.

 

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