Docker Swarm vs. Kubernetes: A comparison

In a nutshell, containers are a standard way to package apps and all their dependencies so that you can seamlessly move the apps between runtime environments. By packaging an app’s code, dependencies and configurations into one easy-to-use building block, containers let you take important steps toward shortening deployment time and improving application reliability.

In enterprise applications, the number of containers can quickly grow to an unmanageable number. To use your containers most effectively, you’ll need to orchestrate your containerized applications, which is where Kubernetes and Docker Swarm come in.

Kubernetes is a portable, open-source platform for managing containers, their complex production workloads and scalability. With Kubernetes, developers and DevOps teams can schedule, deploy, manage and discover highly available apps by using the flexibility of clusters. A Kubernetes cluster is made up of compute hosts called worker nodes. These worker nodes are managed by a Kubernetes master that controls and monitors all resources in the cluster. A node can be a virtual machine (VM) or a physical, bare metal machine.

In the early days of Kubernetes, the community contributors leveraged their knowledge of creating and running internal tools, such as Borg and Omega, two cluster management systems. With the advent of the Cloud Native Computing Foundation (CNCF) in partnership with the Linux Foundation, the community adopted Open Governance for Kubernetes, a set of rules for Kubernetes clusters that help teams operate at scale. IBM, as a founding member of CNCF, actively contributes to CNCF’s cloud-native projects, along with other companies like Google, Red Hat, Microsoft and Amazon.

Advantages of Kubernetes

• Kubernetes offers a wide range of key functionalities, including service discovery, ingress and load balancing, self-healing, storage orchestration, horizontal scalability, automated rollouts/rollbacks and batch execution.
• It has a unified set of APIs and strong guarantees about the cluster state.
• It’s an open-source community (link resides outside of ibm.com) that’s very active in developing the code base.
• Fast-growing KubeCon conferences throughout the year offer user insights.
• Kubernetes has the largest adoption in the market.
• It’s battle-tested by big players like Google and our own IBM workloads, and it runs on most operating systems.
• It’s available on the public cloud or for on-premises use, and it has managed or non-managed offerings from all the big cloud providers (e.g., IBM Cloud, AWS, Microsoft Azure, Google Cloud Platform, etc.).
• There’s broad Kubernetes support from an ecosystem of cloud tool vendors, such as Sysdig, LogDNA, and Portworx (among many others).

Kubernetes challenges

• It has a steep learning curve and management of the Kubernetes master takes specialized knowledge.
• Updates from the open-source community happen frequently and require careful patching to avoid disrupting workloads.
• It’s too heavyweight for individual developers to set up for simplistic apps and infrequent deployments.
• Teams often need additional tools (e.g, kubectl CLI), services, continuous integration/continuous deployment (CI/CD) workflows and other DevOps practices to fully manage access, identity, governance and security.

Docker Swarm is another open-source container orchestration platform that has been around for a while. Swarm — or more accurately, swarm mode — is Docker’s native support for orchestrating clusters of Docker engines. A Swarm cluster consists of Docker Engine-deployed Swarm manager nodes (which orchestrate and manage the cluster) and worker nodes (which are directed to execute tasks by the manager nodes).

Advantages of Docker Swarm

• Docker is a common container platform used for building and deploying containerized applications. Swarm is built for use with the Docker Engine and is already part of a platform that’s familiar to most teams.
• It’s easy to install and set up for a Docker environment.
• Tools, services and software that run with Docker containers will also work well with Swarm.
• It has its own Swarm API.
• It smoothly integrates with Docker tools like Docker Compose and Docker CLI since it uses the same command line interface (CLI) as Docker Engine.
• It uses a filtering and scheduling system to provide intelligent node selection, allowing you to pick the optimal nodes in a cluster for container deployment.

Docker Swarm challenges

• Docker Swarm offers limited customizations and extensions.
• It’s less functionality-rich and has fewer automation capabilities than those offered by Kubernetes.
• There’s no easy way to separate Dev-Test-Prod workloads in a DevOps pipeline.

Not to confuse matters too much, but Docker Enterprise Edition now supports Kubernetes (link resides outside of ibm.com) too.

Now that’s we’ve covered the advantages and challenges, let’s break down the similarities and differences between Kubernetes and Docker Swarm. Both platforms allow you to manage containers and scale application deployment. Their differences are a matter of complexity. Kubernetes offers an efficient means for container management that’s great for high-demand applications with complex configuration, while Docker Swarm is designed for ease of use, making it a good choice for simple applications that are quick to deploy and easy to manage.

Here are some detailed differences between Docker Swarm and Kubernetes:

Installation and setup

Because of the complexity of Kubernetes, Docker Swarm is easier to install and configure.

• Kubernetes: Manual installation can differ for each operating system. No installation is required for managed offerings from cloud providers.
• Swarm: There is simple installation with Docker, and instances are typically consistent across operating systems.

Scalability

Kubernetes offers all-in-one scaling based on traffic, while Docker Swarm emphasizes scaling quickly.

• Kubernetes: Horizontal autoscaling is built in.
• Swarm: Offers autoscaling of groups on demand.

Load balancing

Docker Swarm has automatic load balancing, while Kubernetes does not. However, an external load balancer can easily be integrated via third-party tools in Kubernetes.

• Kubernetes: Discovery of services is enabled through a single DNS name. Kubernetes has access to container applications through an IP address or HTTP route.
• Swarm: Comes with internal load balancers.

High availability

Both tools provide a high level of availability.

• Kubernetes: By diverting traffic away from unhealthy pods, Kubernetes is self-healing. It offers intelligent scheduling and high availability of services through replication.
• Swarm: Swarm Managers offer availability controls, and microservices can be easily duplicated.

Like most platform decisions, the right tool depends on your organizations’ needs.

Kubernetes has widespread adoption and a large community on its side. It is supported by every major cloud provider and do-it-yourself offerings like Docker Enterprise Edition. It is more powerful, customizable and flexible, which comes at the cost of a steeper initial learning curve. It requires a team that’s experienced and capable of running it; however, companies are also opting to use a managed service provider to simplify open-source management responsibilities and allow them to focus on building applications.

Docker Swarm’s advantage comes with familiarity and emphasis on ease-of-use. It is deployed with the Docker Engine and is readily available in your environment. As a result, Swarm is easier to start with, and it may be more ideal for smaller workloads.

Now that you’ve covered the differences between Kubernetes and Docker Swarm, take a deeper dive in the IBM Cloud Kubernetes Service and learn how to build a scalable web application on Kubernetes.

Want to get some free, hands-on experience with Kubernetes? Take advantage of IBM CloudLabs, a new interactive platform that offers Kubernetes tutorials with a certification—no cost or configuration needed.

• IBM Cloud Kubernetes Service
• What is Kubernetes?
• Kubernetes Tutorials: 5 Ways to Get You Building Fast
• Kubernetes Clusters: Architecture for Rapid, Controlled Cloud App Delivery
• Kubernetes vs. Docker: Why Not Both?