Setup Docker Swarm Cluster on Ubuntu 22.04

Welcome to our guide on how to Setup Docker Swarm Cluster on Ubuntu 22.04. Docker is a technology that makes it simple to develop, test, and deploy applications utilizing containers. It offers a simple environment for deploying and running applications. A cluster of physical or virtual machines that are all executing the same program under the name “docker” is known as a “docker swarm.”

Setup Docker Swarm Cluster on Ubuntu 22.04

The steps below will guide you through the configuration and Setup of Docker Swarm Cluster on Ubuntu 22.04.

Prerequisites

Here are the requirements for us to set up a complete and functional Docker Swarm Cluster on Ubuntu 22.04.

• Server a Manager hostname(dockermanager.dockerswarm.com) IP- 192.168.56.101
• Server b Node 1 hostname(workernode01.dockerswarm.com) IP- 192.168.56.102
• Server c Node 2 hostname(workernode02.dockerswarm.com) IP- 192.168.56.103

Configure /etc/hosts file

Using the editor of your choice, edit /etc/hosts files in all the 3 servers;

sudo vim /etc/hosts

Add the following content to the file, replacing the IP addresses with your own;

192.168.56.101    dockermanager.dockerswarm.com   dockermanager
192.168.56.102    workernode01.dockerswarm.com         workernode01
192.168.56.103    workernode02.dockerswarm.com         workernode02

Install Docker CE on Ubuntu 22.04

We are going to install Docker CE in all three hosts as follows:

Update the hosts;

sudo apt update

Run the command below to install dependent packages;

sudo apt install apt-transport-https ca-certificates curl software-properties-common lsb-release

Run the following command to add a docker key to the hosts;

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/docker-archive-keyring.gpg

Run the following command to add a docker repository to the hosts;

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

Run system updates in all the hosts;

sudo apt update

Now, install Docker CE on the three hosts;

sudo apt install docker-ce

Check the status of the docker in each host;

systemctl status docker

Output;

● docker.service - Docker Application Container Engine
     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-09-19 18:50:29 UTC; 24s ago
TriggeredBy: ● docker.socket
       Docs: https://docs.docker.com
   Main PID: 54745 (dockerd)
      Tasks: 9
     Memory: 26.5M
     CGroup: /system.slice/docker.service
             └─54745 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

Configure Docker Swarm Cluster on Ubuntu 22.04

To setup Docker Swarm, we need to initialize Docker Swarm mode on the DockerManager host.

Run the following command to initialize the Docker Swarm. Replace the IP address with the DockerManager host IP;

 sudo docker swarm init --advertise-addr 192.168.56.101

Here is the output of the above command;

Swarm initialized: current node (f2rkkojrrk332jyh3fmvttpmq) is now a manager.

To add a worker to this swarm, run the following command:

    sudo docker swarm join --token SWMTKN-1-5ct25i0lj0zoocnefpj8sxjoarr4tto6krn5d6u0amx2ae51wj-0qfth1kbbc88bh8jpcwhjini0 192.168.56.101:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

From the above output, we got the token for joining the worker nodes to the cluster;

sudo docker swarm join --token SWMTKN-1-5ct25i0lj0zoocnefpj8sxjoarr4tto6krn5d6u0amx2ae51wj-0qfth1kbbc88bh8jpcwhjini0 192.168.56.101:2377

Join WorkerNodes To the Docker Swarm Cluster

To join the two worker nodes(WorkerNode01 and WorkerNode02), we will use the token generated from the master node(Dockermanger).

On WorkerNode01, run the following command to join it to the cluster;

sudo docker swarm join --token SWMTKN-1-5ct25i0lj0zoocnefpj8sxjoarr4tto6krn5d6u0amx2ae51wj-0qfth1kbbc88bh8jpcwhjini0 192.168.56.101:2377

This node joined a swarm as a worker.

On WorkerNode02, run the following command to join it to the cluster;

sudo docker swarm join --token SWMTKN-1-5ct25i0lj0zoocnefpj8sxjoarr4tto6krn5d6u0amx2ae51wj-0qfth1kbbc88bh8jpcwhjini0 192.168.56.101:2377

This node joined a swarm as a worker.

Now, verify if the nodes have been added successfully to the Docker Swarm cluster.

Run the following command on DockerManager;

sudo docker node ls

ID                            HOSTNAME        STATUS    AVAILABILITY   MANAGER STATUS   ENGINE VERSION
f2rkkojrrk332jyh3fmvttpmq *   dockermanager   Ready     Active         Leader           24.0.2
tgthmz9ugmx8obplm6gq4q1pj     workernode01    Ready     Active                          24.0.2
xm0dueep1q5f55z7i46jbxebp     workernode02    Ready     Active                          24.0.2

Deploying an Application on the Docker Swarm Cluster

Tasks are launched as services in place of containers in Docker Swarm. We will run the following command on DockerManager(master node) in order to deploy our first application on the Docker Swarm cluster. In this example, we will deploy the Nginx application on its default HTTP port 80;

sudo docker service create --name web-server --publish 80:80 nginx:latest

ldkp699sulrnj0t37cuursbk0
overall progress: 1 out of 1 tasks 
1/1: running   [==================================================>] 
verify: Service converged 

Check the service created;

sudo docker service ls

ID             NAME         MODE         REPLICAS   IMAGE          PORTS
ldkp699sulrn   web-server   replicated   1/1        nginx:latest   *:80->80/tcp

Run the following command to check the status of the service;

sudo docker service ps web-server

ID             NAME           IMAGE          NODE            DESIRED STATE   CURRENT STATE            ERROR     PORTS
4avf5yvbnzil   web-server.1   nginx:latest   dockermanager   Running         Running 12 minutes ago

Accessing the Nginx Web Service

As of right now, we are aware that the service is active on every node, including the Docker Manager. Let’s try accessing the addresses below on the web browser;

• http://192.168.56.101
• http://192.168.56.102
• http://192.168.56.103

You will be able to get a page similar to the one below:

This shows that our Nginx application is running on all the nodes successfully.

Scaling Up the Nginx service on Docker Swarm Cluster

We will replicate the web-server service six times and make it available on the docker manager and two worker nodes.

Run the following command on DockerManager to scale up or replicate the web-server service on Docker Swarm;

sudo docker service scale web-server=6

Output;

web-server scaled to 6
overall progress: 6 out of 6 tasks 
1/6: running   [==================================================>] 
2/6: running   [==================================================>] 
3/6: running   [==================================================>] 
4/6: running   [==================================================>] 
5/6: running   [==================================================>] 
6/6: running   [==================================================>] 
verify: Service converged

We can check the created replicas as follows;

sudo docker service ls

ID             NAME         MODE         REPLICAS   IMAGE          PORTS
ldkp699sulrn   web-server   replicated   6/6        nginx:latest   *:80->80/tcp

We can also check the running services after scaling up;

sudo docker service ps web-server

Output;

ID             NAME           IMAGE          NODE            DESIRED STATE   CURRENT STATE               ERROR     PORTS
4avf5yvbnzil   web-server.1   nginx:latest   dockermanager   Running         Running about an hour ago             
se6bn1zth5i9   web-server.2   nginx:latest   dockermanager   Running         Running 4 minutes ago                 
padgpve4uhot   web-server.3   nginx:latest   workernode01    Running         Running 4 minutes ago                 
5gmc6l5j94o9   web-server.4   nginx:latest   workernode01    Running         Running 4 minutes ago                 
fn6lk85v40ty   web-server.5   nginx:latest   workernode02    Running         Running 4 minutes ago                 
dzkmy4y3ukru   web-server.6   nginx:latest   workernode02    Running         Running 4 minutes ago

Scaling Down the Nginx service on Docker Swarm Cluster

On DockerManager we can also scale down web-server service to any number we require. In this example, we will scale down the web-server service to four.

Run the following command to scale down the web-server service on Docker Swarm;

sudo docker service scale web-server=4

Output;

web-server scaled to 4
overall progress: 4 out of 4 tasks 
1/4: running   [==================================================>] 
2/4: running   [==================================================>] 
3/4: running   [==================================================>] 
4/4: running   [==================================================>] 
verify: Service converged

We can check the created replicas as follows;

sudo docker service ls

ID             NAME         MODE         REPLICAS   IMAGE          PORTS
ldkp699sulrn   web-server   replicated   4/4        nginx:latest   *:80->80/tcp

Now, check the running services after scaling down;

sudo docker service ps web-server

Output;

ID             NAME           IMAGE          NODE            DESIRED STATE   CURRENT STATE               ERROR     PORTS
4avf5yvbnzil   web-server.1   nginx:latest   dockermanager   Running         Running about an hour ago             
se6bn1zth5i9   web-server.2   nginx:latest   dockermanager   Running         Running 13 minutes ago                
padgpve4uhot   web-server.3   nginx:latest   workernode01    Running         Running 12 minutes ago                
fn6lk85v40ty   web-server.5   nginx:latest   workernode02    Running         Running 13 minutes ago