Docker Swarm

Docker Swarm is a native Docker orchestration tool that allows you to deploy and manage multiple Docker containers as a single unit. In this article, we’ll cover the basic setup of Docker Swarm, including creating a swarm, adding nodes, and deploying a service.

Prerequisites

• Docker installed on multiple machines (nodes)
• Docker version 1.12 or later
• All nodes must be able to communicate with each other

Step 1: Create a Swarm

On one of the nodes, run the following command to create a new swarm:

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docker swarm init

This command will create a new swarm and make the current node the manager node.

Step 2: Add Nodes to the Swarm

On each additional node, run the following command to join the swarm:

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docker swarm join <manager-node-ip>:2377

Replace <manager-node-ip> with the IP address of the manager node.

Step 3: Verify the Swarm

Run the following command on the manager node to verify the swarm:

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docker node ls

This command will list all nodes in the swarm, including their status and roles.

Step 4: Deploy a Service

Create a new service using the following command:

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docker service create --name myservice --replicas 3 -p 8080:80 nginx

This command will create a new service named “myservice” with 3 replicas, exposing port 8080 on the host and mapping it to port 80 in the container.

Step 5: Verify the Service

Run the following command to verify the service:

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docker service ls

This command will list all services in the swarm, including their status and number of replicas.

Basic Swarm Architecture

Here’s a high-level overview of the basic swarm architecture:

• Manager Node: The node that creates and manages the swarm.
• Worker Nodes: The nodes that join the swarm and run services.
• Services: The applications or containers that are deployed and managed by the swarm.

That’s it! You now have a basic Docker Swarm setup with a single service running on multiple nodes. From here, you can explore more advanced features and configurations to suit your needs.