Sometimes it’s hard to decide whether you should use one service or another. The IT market has its leaders, but you have to find a leader for yourself. So, if container orchestration is on your mind now, read on to figure out why Kubernetes or Docker Swarm are popular among DevOps engineers and what makes them different.
From chaos to order: Container orchestration
Over the last few years, containers have become an integral part of software deployment. Used to package the application’s code and its dependencies, they ensure quick and consistent application deployments.
Containerization makes distributed application development optimized and efficient and is essential for the microservice architecture. Each container operates autonomously, therefore such flexibility helps to prevent interdependencies and ensures that there would be no single point of failure. Once the application grows, it causes no troubles for DevOps engineers to distribute the loads and ensure high availability.
However, another problem arises. The more containers (there can be hundreds or thousands of them) you have in your infrastructure, the more challenges you experience during deployment. It may cause a mess. To turn the chaos to perfect order, you need to manage those containers.
For dynamic and large infrastructures, container orchestration is the only advanced solution. For this purpose, you can use such services as Kubernetes or Docker Swarm. They control and automate such tasks as application configuration, load balancing, provisioning, networking, high availability, scaling, allocation of resources, health monitoring.
Let’s talk about majors now. Kubernetes and Docker Swarm are destined to manage containers. Both offer vast capabilities, and even though they have the common goal, their ways to achieve it are rather unique.
What is Kubernetes?
Kubernetes is a robust container orchestration system allowing scaling and automation of application processes across the clusters of hosts. It allows easy management of operations while coupling containers into logical units. Kubernetes defines how the application should run and how it interacts with other applications. Those who are using Kubernetes agree – it is a front-runner for container orchestration, offering flexibility, environment-agnostic portability, and painless scaling.
What is Docker Swarm?
Docker has taken care of having its own system for container orchestration – Docker Swarm. So, it is a very convenient solution for those who are already familiar with the platform. Swarm is developed for packaging and distributing containerized applications. It allows creating a resilient and secure architecture and backward-compatibility with existing components.
Kubernetes vs. Docker
Kubernetes has alternatives for some Docker commands, such as docker run (kubectl run), docker exec, docker attach etc. So, for some cases, Docker users may use the familiar way to run containers (but that’s not the primary way, of course). With Docker Swarm, it is easier to run a container (can be done with a single command). It is perfectly compatible with various Docker tools, but creates a problem when those are deficient.
Kubernetes networking model presents a flat network where all pods communicate across multiple nodes. The flat network is implemented as an overlay. The overlay network is also typical for Swarm. It is generated by the node joining a swarm cluster.
Ensuring scalability for Kubernetes is quite a complex process, because of a unified set of APIs and focus on the cluster state. This makes scaling and deployment with Kubernetes slower than with Swarm. Though, auto-scaling is much faster with the former since it analyzes the server load and scale services up to your requirements. Docker Swarm, in its turn, deploys containers way faster which makes possible quick reaction times to scale on demand.
In Kubernetes, you create Services (Kubernetes-specific object type) which are connected to the respective Pods using selectors and labels, and while having several Pods’ replicas (either on different nodes or on the same node), Services allow for round-robin load balancing between different Pods’ replicas. Sometimes you may need to configure the settings manually to balance the traffic between containers in different pods. Docker Swarm offers auto load balancing of traffic. All containers create one network in a single cluster, so you can connect any node to any container.
Kubernetes distributes all the pods among nodes. This allows tolerating the failure of the application. Load balancing services detect unhealthy pods and eliminate them, using Liveness probes, or just throw out of round-robin balancing using Readiness probes. What about Swarm, it restarts the containers on the different host once the current host experiences a failure. So, both services ensure high availability just fine.
Both services are effective solutions for container orchestration but they have some differences. Kubernetes supports more complex tasks and fulfills higher demands, while Docker Swarm offers a much simpler yet quick way to manage your containers. Therefore, if you choose simplicity, fast deployments, and prefer the Docker ecosystem, Swarm may be a good service for your needs. But if your application demands are more sophisticated, Kubernetes would be a better choice.