Docker Swarm — first steps with container orchestration

Docker on a single server is great. On ten servers you need orchestration: placement, scaling, networking, rolling updates, self-healing.

Swarm mode¶

docker swarm init --advertise-addr 10.0.1.10
docker swarm join --token SWMTKN-1-xxx 10.0.1.10:2377
docker service create --name web --replicas 3 -p 80:80 nginx:1.9
docker service scale web=5

Services define the desired state. The Swarm manager performs reconciliation — when a node goes down, containers are moved to healthy nodes. Overlay networking is automatic.

Rolling updates¶

docker service update --image myapp:2.0 web — updates containers one by one, without downtime. Configurable parallelism and delay.

Swarm vs. Kubernetes¶

Swarm is simpler and integrated in Docker. Kubernetes is more powerful but more complex. Use Swarm for smaller clusters; for larger deployments, Kubernetes is likely the answer.

Orchestration is a must for production¶

Without orchestration you are running containers like virtual machines — wasting their potential.