Kubernetes vs Docker Swarm: What are the practical differences?

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If you've worked with containers, you know that orchestration is essential for managing applications at scale. The two names that always come up in this discussion are Kubernetes and Docker Swarm. Both are powerful tools, but each has its own way of doing things. But what are the practical differences?

1. Docker Swarm has a quicker start

If you're just starting out in the world of container orchestration, Docker Swarm might be the more user-friendly choice. It now comes integrated with the Docker Engine upon installation, and with just a few commands, you can create a cluster and manage your services.

For example, to start a cluster in Docker Swarm, simply run:

docker swarm init

And to add a service:

docker service create --name meu_servico --replicas 3 minha_imagem

Pretty simple, right? On the other hand, Kubernetes has a steeper learning curve, requiring the use of multiple YAML files. The initial setup can be intimidating and complex, especially if you're setting up a cluster from scratch (and without using ArgoCD). Tools like Minikube or kubeadm can help, but Kubernetes still requires a deeper understanding of concepts like Pods, Services, Deployments, and Namespaces.

 

2. Kubernetes to infinity and beyond

When it comes to scalability, Kubernetes is king. It was designed to handle massive workloads and highly distributed environments. Companies like Google, Spotify, and Airbnb use Kubernetes to manage thousands of containers in production.

Kubernetes already has robust support for auto-scaling out of the box. Other features that make Kubernetes more scalable include its powerful self-healing system and intelligent scheduling, which handle many complex tasks for us with ease.

Docker Swarm is more limited in these areas. It scales well for smaller or medium-sized projects, but it may not be the best choice for environments that require more complex orchestration or involve thousands of nodes.

 

3. Their ecosystems

Being older and extremely popular, the Kubernetes ecosystem is vast and constantly growing. There are tools for almost everything: monitoring (Prometheus, Grafana), secret management (HashiCorp Vault), CI/CD (ArgoCD, Jenkins), and much more. Additionally, Kubernetes is widely supported by cloud services like Azure, AWS, and GCP.

Docker Swarm is also quite popular, but it hasn't been as widely adopted by the community as Kubernetes, and as a result, it has fewer resources and tools available. It works well for simpler use cases, but it doesn't offer the same flexibility and variety of tools as Kubernetes. If you need something beyond the basics, you might find yourself missing some features.

 

4. But Rui, which one do you recommend?

After analyzing these points, we can come to a simple conclusion: Do you need to deploy a few services without much complexity and with some speed? Use Docker Swarm. In this case, Kubernetes would be overkill for your project, both in terms of complexity and cost. But if your environment will run distributed across multiple servers, requires nearly 100% uptime, needs various observability tools, and involves complex communication between your microservices? Use Kubernetes. Your environment will be much more robust and prepared for such intensive workloads.

 

5. Let's get our hands dirty

A small example of using both tools:

Docker Swarm:

1. Start the cluster:

   docker swarm init

1. Create a service:

   docker service create --name web --replicas 3 -p 80:80 nginx

Done! Your nginx is running with 3 replicas.

Kubernetes:

1. Create a Deployment:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: web-deployment
   spec:
     selector:
       matchLabels:
         app: web
     template:
       metadata:
         labels:
           app: web
       spec:
         containers:
         - name: nginx
           image: nginx
           ports:
           - containerPort: 80

1. Create a Service to expose the Deployment:

   apiVersion: v1
   kind: Service
   metadata:
     name: web-service
   spec:
     selector:
       app: web
     ports:
       - protocol: TCP
         port: 80
         targetPort: 80
     type: LoadBalancer

1. Create an HPA to configure AutoScaling:

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: web-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: web-deployment
  minReplicas: 1
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: memory
        target:
          averageUtilization: 80
          type: Utilization

1. Apply the YAML files:

   kubectl apply -f deployment.yaml
   kubectl apply -f service.yaml
   kubectl apply -f hpa.yaml

As you can see, Docker Swarm is more straightforward, while Kubernetes requires a bit more configuration.

 

Conclusion

Both Kubernetes and Docker Swarm have their strengths and weaknesses. The right choice depends on your project's needs and your familiarity with the tools.

Have you used any of these tools? What was your experience? Share in the comments!

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This article was entirely written by me, utilising AI only for text correction.