Kubernetes and Docker Compose are two of the most popular technologies used to run containers. They each allow you to work with multiple containers simultaneously, such as your application, a database, and a caching layer, which makes it easier to implement real-world use cases.
What is the difference between Docker Compose and Kubernetes? There’s significant overlap between the two tools, but there are also key differences that make them best suited to individual use cases. In this article, we’ll evaluate both options and discuss which scenarios they’re built for. Let’s begin!
Kubernetes is a container orchestrator. It’s designed to help you deploy and scale containerized workloads in production environments that demand high availability.
Kubernetes distributes replicas of your containers across multiple physical compute Nodes. This results in fault-tolerant deployments that keep your app accessible, even if one of your Nodes experiences problems. The ability to endlessly add new Nodes lets you horizontally scale your services to match capacity to usage.
Kubernetes use cases
As a production-grade orchestration solution, Kubernetes is a great option for running your container workloads in live environments. It’s a particularly good fit for microservices architectures, where your app is composed from multiple containerized services that need to be individually scaled but networked together. The flexible scheduling and networking capabilities available in Kubernetes mean it easily fulfills these criteria.
Other Kubernetes use cases include:
- Simplifying multi-cloud deployments, such as by joining worker Nodes in different clouds to one cluster control plane.
- Allowing on-demand and self-service deployment of staging and test environments.
- Improving multi-tenant deployments for multiple apps, teams, and customers.
- Hosting AI, ML, and big data workloads, where massive processing power is required.
- Providing a foundation for your own higher-level tooling and internal developer platforms.
The biggest drawback of Kubernetes is its complexity and relatively steep learning curve. It includes so many features and unique concepts that even experienced container developers can require a lengthy familiarization period. As a result, Kubernetes is sometimes considered less suitable for local development scenarios where deployments don’t need robust high availability.
Docker Compose is a tool that’s used to build and run multi-container applications with Docker, the most popular containerization solution for developers. Whereas Docker only lets you interact with one container at a time, Compose gives you the ability to define your app’s services in a config file, then bring up all the containers using a single command.
Compose simplifies the developer experience by making it easier and more repeatable to launch a fully-functioning deployment of your app and its dependencies. You can use all the familiar Docker features but benefit from easier network and storage management. Your configuration will be reliably reapplied each time you use Compose to start your containers.
Docker Compose use cases
Docker Compose can be used anytime you want to establish a consistent versioned configuration for your containers, or need to bring up multiple containers to run your application. Its ease of use makes it a popular option for developers to install on their own machines, but Compose may also be found in production environments.
Common Docker Compose use cases include:
- Running multiple instances of an application on one host.
- Making it easier for other developers to test out an application with its dependencies.
- Developing a container stack locally, then deploying the same configuration to another environment.
This list demonstrates how Compose is positioned as a developer-facing tool. It accelerates key container management tasks by condensing otherwise long-winded operations down to a few commands.
With the use cases out of the way, now let’s compare how Kubernetes and Docker Compose stack up side-by-side. The following lists aren’t meant to be exhaustive, but they provide an overview of some of the most noteworthy similarities and differences to be aware of.
1) Both support multiple containers
Kubernetes and Docker Compose are both multi-container tools. You can easily start several containers simultaneously and work with them in aggregate, facilitating more convenient interactions with your workloads. Both systems use YAML files to define your containers and their configurations.
2) Both handle container networking
Correctly linking containers together can be challenging; Kubernetes and Docker Compose remove some of the headaches by handling basic networking for you. In the case of Kubernetes, all containers join a cluster-spanning flat network that allows them to auto-discover each other and you can use Services to load balance between containers. Compose’s networking model is simpler but easier to learn, with all containers in your stack automatically sharing a network connection.
Read more about Kubernetes networking.
3) Support simple configuration of storage volumes
Either tool can be used to run containers that have persistent storage requirements. In the case of Kubernetes, Persistent Volumes abstract away the differences between storage implementations such as a local drive or cloud block storage volume. Compose doesn’t offer cloud integrations but still lets you easily configure local volumes that will always be remounted to your containers.
4) Each manages the container lifecycle for you
Kubernetes and Docker Compose take the pain out of container lifecycle management. They make it easier to start all your containers in the correct order, collect their output, and then stop redundant services. They also include variations of auto-healing functionality to ensure your workloads restart themselves after failure.
The similarities outlined above make it clear that Kubernetes and Docker Compose are both useful to container developers and operators. However, while they’re certainly complementary tools, they’re arguably better defined by their differences than what they have in common.
1) Only Kubernetes is specifically designed for orchestration of distributed systems
Kubernetes is designed to support the requirements of containerized workloads in production. It’s a purpose-built orchestrator for deploying and managing containers across hundreds or thousands of compute Nodes. Compose can manage distributed deployments, but you need to use Docker’s separate Swarm feature, which isn’t core to the Compose offering. Swarm has less functionality and much narrower adoption than Kubernetes.
2) Kubernetes supports auto-scaling
Kubernetes can auto-scale your deployments in response to changes in utilization. If there’s an influx of traffic, you can start new container replicas or even provision additional cluster Nodes without having to manually intervene. Compose doesn’t support this behavior, and it’s not available within Docker Swarm either.
3) Compose directly manages containers, whereas Kubernetes works with higher-level Pods
Compose provides a relatively thin interaction layer on top of the regular Docker experience. You’re still directly interacting with Docker containers as your fundamental compute unit. Kubernetes adds its own concepts to the architecture: you create and manage Pods, which can each hold multiple containers. This provides extra flexibility when you’re defining your workloads, but can be a source of confusion for newcomers.
4) Kubernetes is self-healing
Kubernetes is fully self-healing. If a container terminates or a Node fails, a replacement Pod replica will automatically start in a healthy part of your cluster—without users ever noticing. As Compose is generally a single-host tool, it can’t offer this level of redundancy. You can configure containers to auto-restart after a failure, but this doesn’t handle situations such as a Docker runtime failure or a physical host outage.
5) Kubernetes supports scheduled jobs
Kubernetes is more than just a container orchestrator—it’s a complete platform for building and running your applications. The ability to run one-off and scheduled jobs allows you to more easily implement complex container-adjacent functionality without manually configuring system crontabs or polluting your containers with extra processes.
6) Compose is primarily a local tool
Compose’s local-first mentality, compared to the Kubernetes emphasis on multi-host deployments with almost limitless scalability, is still the foremost difference between the tools. Swarm mode means Compose can be used with multiple hosts, but this doesn’t come close to matching the direct cloud integrations and managed provisioning options that are prevalent in the Kubernetes ecosystem.
Still unsure how Kubernetes and Docker Compose compare, or need a handy reference to their similarities and differences? Here’s a quick comparison table.
Kubernetes and Docker Compose are tools designed for slightly different but overlapping use cases. Therefore, you might find that you want to use Kubernetes for some of your work—such as running apps in production—while you rely on Docker Compose for other tasks, like local development.
Using Kubernetes and Docker Compose together like this is often a pragmatic way for DevOps teams to achieve their goals. Compose simplifies common developer scenarios, where distributed deployments and high availability are less important, while Kubernetes provides those extra capabilities to ops teams tasked with maintaining stable live environments.
One important caveat is that Kubernetes and Docker Compose can’t interact with each other. Both are standalone tools with their own config files and CLIs so it’s not possible to directly utilize Docker Compose within your Kubernetes deployments, or vice versa. Tools like Kompose help convert from Docker Compose to Kubernetes with minimal effort, but going in the opposite direction is harder because Kubernetes has many additional features that don’t map back to any Compose counterpart.
Spacelift helps you manage the complexities and compliance challenges of using Kubernetes. It brings with it a GitOps flow, so your Kubernetes Deployments are synced with your Kubernetes Stacks, and pull requests show you a preview of what they’re planning to change. It also has an extensive selection of policies, which lets you automate compliance checks and build complex multi-stack workflows.
You can also use Spacelift to mix and match Terraform, Pulumi, CloudFormation, and Kubernetes Stacks and have them talk to one another. For example, you can set up Terraform Stacks to provision the required infrastructure (like an ECS/EKS cluster with all its dependencies) and then deploy the following via a Kubernetes Stack.
When you’re working with containers, the Docker CLI alone doesn’t cut it for long. Docker Compose allows you to create stacks of containers that you can interact with collectively, while Kubernetes lets you easily scale container replicas across multiple physical hosts. These are essential capabilities for building and running most real-world containerized systems.
As we’ve seen in this article, the tools share some similarities, but they also have significant differences. Kubernetes is generally a better fit for operating containers in production with massive scalability and reliability demands. Docker Compose’s simplicity and ease of use mean it’s often the preferred option for local developer use, as it has a much lower initial learning curve. Fortunately, you don’t have to choose between the tools—many DevOps teams successfully use both Docker Compose and Kubernetes, providing access to the benefits of both.
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