Kubernetes vs Docker Swarm: A Container Orchestration Tools Comparison
As more and more applications move to the cloud, their architectures and distributions continue to change. With the change, comes the need for tools and skills that can help in managing distributed topology across the cloud.
Since Linux first introduced the concept of containerization around a decade ago, many developer teams have switched to containers over traditional virtual machines infrastructure setup. Containerization platforms like Docker have made the deployment of the application easier, enabling teams to handle all of their microservices.
However, as the number of containers in the system grows, the need for something that can help with the orchestration of these containers grows. And that’s where Kubernetes and Docker Swarm enter the picture.
Problems Container Orchestration Solves
Businesses around the world rely on container technology to ease the deployment and management of complex applications. Containers package up code along with all its dependencies and libraries to allow an application to run efficiently and reliably on different computing environments. But it doesn’t do much about how a container fits into a system, its load balancing, a container's lifecycle, readiness, or health.
Containers can’t surface a scalable, reliable, and fault-tolerant service by itself. Docker only knows that the lifecycle of its container starts and ends with the given process. So containerization platforms like Docker need some additional tool or service to coordinate and command these containers.
So here enter the container orchestration platforms.
Container orchestration refers to the automation of deployment, networking, management, and scaling of containers. Businesses that require deployment and management of hundreds or thousands of containers can benefit from container orchestration. Kubernetes and Docker Swarm are the most prominent container orchestration platforms.
You can use container orchestration wherever you use containers, regardless of their environment. With container orchestration, you can deploy the same application across multiple environments without redesigning it.
Container orchestration tools are used to automate and manage tasks like provisioning, deployment, configuration, scheduling, container availability, load balancing, traffic routing, resource allocation, container health monitoring, securing interaction between containers, and scaling or removing containers for balancing workloads across the infrastructure.
But before we move ahead with the comparison of Kubernetes and Docker Swarm, let’s first get a quick overview of these two tools.
What is Kubernetes?
Kubernetes (K8s or Kube) is an open-source, portable, extensible container orchestration platform for containerized services and workloads management. Originally developed by Google, it was eventually handed over to the Cloud Native Computing Foundation (CNCF) for maintenance and enhancements. Kubernetes has a more complex structure than Docker Swarm. The cluster of Kubernetes includes a set of worker nodes (worker machine) that host Pods (a set of running containers) and its control plane (container orchestration layer) manages the Pods and worker nodes in the cluster.
Pros of Kubernetes
Large and active open-source community backed by Google.
Sustain and handle large architectures and complex workloads.
Supports all operating systems.
Key functionalities consist of ingress, load balancing, service discovery, horizontal scalability, storage orchestration, self-healing, batch executions and automated rollouts and rollbacks.
Availability on both on-premise and public cloud from cloud providers like Google Cloud Platform, AWS, Microsoft Azure, and IBM Cloud.
Cons of Kubernetes
Extremely heavy for developers who want to set up simple apps with infrequent deployments.
Quick updates from the open-source community require careful patching to avoid workload disruption.
Mostly requires add-on tools, services, CI/CD workflows, and other DevOps practices to handle access, identity, security and governance.
What is Docker Swarm?
Docker Swarm or Swarm is also an open-source container orchestration platform that is native to the Docker platform. Like Kubernetes, Docker Swarm manages containers and was created to ensure that the application runs seamlessly across multiple nodes sharing the same containers. Swarm allows developers to effectively manage, deploy and scale node clusters on Docker.
Docker Swarm consists of multiple Docker hosts that run in swarm mode. The Swarm cluster consists of Docker Engine deployed manager nodes (to orchestrate and manage the cluster) and worker nodes (run swarm services). At the time you create a service and define its optimal state including the number of networks, replicas, storage resources available and so on. Docker then works to maintain that desired state.
Pros of Docker Swarm
Has its Swarm API.
Easy integration with Docker tools like Docker CLI and Docker Compose.
Any service, tools or software that works on a Docker container will effortlessly work with Swarm.
Simple installation and set-up process for Docker environment.
Provide intelligent node selection using a filtering and scheduling system that enables developers to opt for the ideal nodes in a container deployment cluster.
Cons of Docker Swarm
Less functionality than Kubernetes
Limited extensions and customizations
A complicated way to separate Dev-Test-Prod workloads in the DevOps pipeline.
Kubernetes vs Docker Swarm: A Head-to-Head Comparison.
So far we have discussed the basic concept of Kubernetes and Docker Swarm along with their pros and cons. It’s time to do a simple head-to-head comparison of both.
Kubernetes and Docker Swarm are both effective solutions for large scale application deployment, implementation and management.
Both models divide applications into containers to efficiently automate application management and scaling.
Read: What is OLAP Analysis?
When it comes to differences between Kubernetes and Docker Swarm, here’s the general summary:
Kubernetes emphasizes open-source, modular orchestration for high-demand applications having complex configurations.
Docker Swarm, on the other hand, focuses on ease of use, making it suitable for simple applications that are easy to manage and quick to deploy.
That being said, let’s look at their fundamental differences in how they operate.
Installation and Set-Up
Kubernetes: Kubernetes has a complex, manual installation process and a steeper learning curve. You have to download and install Kubectl (Kubernetes Command Line Interface) to set up Kubernetes, where the instructions for installation are different for every operating system. Once you are past the installation phase and understand its working, Kubernetes provides stronger clusters that are secured and fast in large production.
Docker Swarm: Compared to Kubernetes, Docker Swarm is easy to install. Assuming that the user has Docker Engine installed on a machine, you only need to establish a manager node and worker nodes for Swarm initialization, assign the IP addresses to hosts and open the ports and protocols between them.
Defining and Deploying Applications
Kubernetes: Kubernetes deployments provide declarative updates to applications. You can define the desired state in a Deployment and the Deployment Controller (a control loop) changes the actual state to the desired state. Deployments can be defined to create new ReplicaSets, declare the new Pods state, roll back to an earlier revision of deployment, scale the deployment for more load, clean up older ReplicaSets, and so on.
Docker Swarm: In Docker Swarm, you can define and deploy an application using Swarm files that are predefined to describe the application state. You will need to copy the Docker Compose File at the root to leverage its multiple node machine capabilities and run containers on any number of networks and machines.
Kubernetes: It supports autoscaling on the cluster level via Cluster Autoscaling and the pod level through Horizontal Pod Autoscaler. Acting as an all-inclusive network for distributed nodes, Kubernetes offers strong unified API sets and cluster states.
Docker Swarm: Deploying containers is faster in Docker Swarm and allows on-demand scaling. In order to scale Docker containers, you need to replicate the number of connections to the application. So you can easily scale applications according to your requirements.
Kubernetes: By default, Kubernetes allows two topologies that ensure the high availability of applications by creating clusters to remove the single point of failure. You can either use Stacked Control Plane nodes that co-locate etcd objects with available nodes of a cluster to ensure availability or use external etcd objects for load balancing while controlling the control plane nodes individually.
Docker Swarm: Docker uses replication of services at the Swarm Nodes level. This allows Swarm managers to deploy multiple instances of the same container with replicas to form highly available, load-balanced clusters.
Graphical User Interface (GUI)
Kubernetes: Kubernetes provides an easy to use dashboard that helps in deploying containerized applications on the cluster, managing resources of the cluster, and viewing error logs on the cluster resource state for troubleshooting.
Docker Swarm: Docker Swarm does not have an out-of-the-box Web UI to deploy and orchestrate containers. But there are some third-party tools like Dock Station, Portainer, and Swarmpit, that can provide a feature-rich GUI for Docker Swarm.
Kubernetes: A flat, peer-to-peer connection between node agents and pods is created in Kubernetes for structured inter-cluster networking. This connection consists of network policies to regulate communication while assigning different IP addresses to the pods.
Docker Swarm: Two types of networks for every node are created by Docker Swarm where one outlines overlay all services within the network and the other creates a host bridge for containers. And a multi-layer overlay network creates peer-to-peer distribution among hosts to achieve secure and encrypted communication.
Kubernetes: It offers multiple native logging and monitoring solutions for deployed services within a cluster. These solutions monitor performance applications by observing cluster behavior and inspecting pods, services and containers. Kubernetes also has third-party integrations like InfluxDB, Sysdig, ElasticSearch, and Kibana to help with event-based monitoring.
Docker Swarm: Usually, monitoring a Docker Swarm is considered a complex task due to its transparent cross node objects and services volume. Also, Docker Swarm does not have its own monitoring solution. So you have to rely on third-party applications to support monitoring. Some tools that can be used for monitoring Docker Swarm are Grafana, InfluxDB and cAdvisor.
Which One is Ideal for Your Business?
As we have discussed in this blog, Docker Swarm is indeed easier to start with and might be ideal for smaller workloads. While Kubernetes is supported by major cloud providers and is popular among most developers as it is more powerful, flexible, and customizable. Although Kubernetes has a steeper learning curve, it still simplifies open-source management responsibilities allowing you to focus on developing your application.
However, when it comes to choosing between the two of them, it entirely depends on the simplicity or complexity of your application. Docker Swarm is preferred in environments where fast development and simplicity is focused and Kubernetes is an ideal fit for medium to large cluster environments for complex applications.