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In this video, you'll get a quick introduction to Docker Swarm.

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So what is Docker Swarm?

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Well, it's a Docker solution to create a cluster or a swarm of multiple Docker hosts.

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It's doing what Kubernetes is doing, basically.

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Before Docker 20, Docker Enterprise Edition was needed to use Swarm.

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But since Docker 20, Docker Swarm is open source and free and doesn't require any license.

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So you can easily take it for a test drive.

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Docker Swarm allows for handling of container scheduling, scaling, networking, and failover

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automatically.

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And you can see it as an easier alternative to Kubernetes.

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It's not as feature rich, but it's pretty easy to get started.

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In order to work with Docker Swarm, you need to be familiar with the terminology.

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So a swarm refers to the entire cluster, which is a group of Docker nodes.

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And nodes are the Docker hosts that are used either as a manager, which controls, or as

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a worker, which runs user workloads.

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A service is the description of what to run.

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And that includes a container image, ports, replicas, and constraints, where replicas

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can be multiple instances of the same container image.

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A task is a specific container that runs in a service.

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And a stack is a collection of services that makes up a microservice application.

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To work with Docker Swarm, you need to know about a couple of commands.

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They all start with Docker Swarm.

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And Docker Swarm init creates a cluster on the first node.

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Docker Swarm join allows other nodes to join the cluster.

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And Docker node ls shows all the nodes in the Swarm cluster.

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Docker service create, minus minus name web, minus p 8080 colon 80, creates a service based

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on the nginx container image and is providing port forwarding to it using port 80.

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Docker service scale, web is five, scales the web service to five running instances.

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And Docker service ls gives a list of services and their replica count.

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Docker stack deploy is a very useful command.

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It deploys a stack as defined in a compose file.

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And Docker service logs gives output generated by all containers in a service.

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Let me give you a quick demo.

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So I'm starting with my Docker Swarm init.

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And that is making that this node is now a manager.

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As you can see, it's printing a join command.

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And the join command is what you can use on other nodes to add them to the Swarm cluster.

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And once you're done building your Swarm cluster, you use Docker service create, minus

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minus name web, minus p 80 colon 80, nginx for instance.

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And as you can see, that is creating the service for you.

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Now Docker service scale is what you can use to add some scalability.

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So let's do a Docker service scale, web is five, to ensure that it's using five different

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instances.

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And then Docker service ls is showing that the service is now running.

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And we have five different replicas on it.

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So it is ready for business.

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And that's enough about Docker Swarm.

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Because after all, Docker Swarm is a topic all by itself.

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And you just need to know a little bit about it.

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This should be enough.