Day 08:Docker Swarm part 1 | RAFT Algorithm | Swarm Commands

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Welcome to the Docker Swarm Setup and Management guide! This guide will walk you through setting up a Docker Swarm cluster, deploying services, and managing the cluster with simple commands.

Introduction

Docker Swarm is a native clustering and orchestration tool for Docker containers. It allows you to manage a cluster of Docker engines as a single virtual system. This guide provides step-by-step instructions to set up and manage your Docker Swarm cluster.

Prerequisites

• Docker installed on all nodes and add ubuntu user to docker group and reboot all instances

• Launch EC2 Instances

  • Launch 6 EC2 instances (Ubuntu 20.04 or later).

  • Assign a Security Group that allows required ports.

  • Ensure all instances use the same VPC and Subnet for private communication.

⚡ Required Ports

• Access to multiple instances (machines or VMs)

Setting Up Docker Swarm

Steps

1. Create 6 EC2 instances: 3 master and 3 worker nodes

   

   

2. 

   Initialize Docker Swarm on the first node: This command initializes the first node as the

    # Initialize Docker Swarm on the first node
    docker swarm init
   

   

3. Join worker nodes: Use the worker join token on each worker node..

    # Join worker nodes
    docker swarm join --token <worker-token> <manager-ip>:<manager-port>
   

   

   

   

4. Join manager nodes: Use the manager join token on each additional manager node.

    # Join manager nodes
    docker swarm join --token <manager-token> <manager-ip>:<manager-port>
   

   

   

   joined rest 2 master nodes as manager

5. Verify the setup: Check the status of the Swarm and list all nodes to ensure they are correctly joined.

    # Check Swarm status
    docker info
    # List nodes
    docker node ls
   

   

   

6. Check networks: View the networks available in the Swarm.

    # Check networks
    docker network ls
   

   

Visualizing the Cluster

Use Swarm Visualizer from GitHub to visualize your cluster. Access the visualizer at http://<manager-ip>:8080.

https://github.com/dockersamples/docker-swarm-visualizer

 docker run -it -d -p 8080:8080 -v /var/run/docker.sock:/var/run/docker.sock dockersamples/visualizer

install visualizer on master server 1

Paste the master server 1 public IP with port 8080 into the browser.

Deploying Services

Steps

1. Deploy a sample service: Create a service with 3 replicas and publish it on port 8000.Commands

    # Deploy a sample service
    docker service create --name nginx-service --replicas 3 --publish 8000:80 nginx
   

   

   

2. Scale the service up and down: Adjust the number of replicas for the service.Commands

   
    # Scale the service up
    docker service scale nginx-service=6
   

   

   

   

   

3. Deploy service only on worker nodes: Ensure the service runs only on worker nodes.

   
    # Deploy service only on worker nodes
    docker service create --name nginx-service --constraint node.role==worker --replicas 6 --publish 8000:80 nginx
   

   

   

   

   

4. Deploy a global service: Run the service on every node.

   
    # Deploy a global service (runs on every node)
    docker service create --name monitor --publish 9100:9100 --mode global prom/node-exporter
   

   

   

Managing Services and Nodes

Steps

1. Check service tasks: List the tasks of a service.Commands

    # Check service tasks
    docker service ps nginx-service
   

   

   

2. Put a node in maintenance mode: Drain the node to prevent it from running tasks.Commands

   
    # Put a node in maintenance mode
    docker node update <node-id> --availability drain
   

   

   

3. Reactivate a node: Set the node back to active status.Commands

   
    # Reactivate a node
    docker node update <node-id> --availability active
   

   

Conclusion

Docker Swarm makes it easy to manage a cluster of Docker containers. With these simple commands, you can set up, deploy, and manage services across multiple nodes. Happy clustering!