Installation of Docker Swarm using Ansible

In this tutorial we will cover how to install Docker Swarm in 2 nodes, 1 master, and 1 worker, using Ansible. For this, we will briefly cover how Ansible itself works and all the necessary steps to make an automated installation of Docker Swarm.

 

What is Ansible?

Ansible is an open-source automation engine that automates software provisioning, configuration management, and application deployment.

As with most configuration management software, Ansible has two types of servers: controlling machines and nodes. First, there is a single controlling machine which is where orchestration begins. Nodes are managed by a controlling machine over SSH. The controlling machine describes the location of nodes through its inventory.

To orchestrate nodes, Ansible deploys modules to nodes over SSH. Modules are temporarily stored in the nodes and communicate with the controlling machine through a JSON protocol over the standard output. When Ansible is not managing nodes, it does not consume resources because no daemons or programs are executing for Ansible in the background.

Docker Swarm is a native Docker application commonly used to manage clusters, which allows orchestrating containers between different nodes easily.

The first thing needed when installing Ansible is creating the inventory file where we will declare all the hosts where we are going to install the services.

For this tutorial we are going to make the installation in AWS using 2 EC2, each one with CentOS7, with the following configuration:

 

Now create the ansible and inventory directories.

Inside the inventory directory, we are going to create the “hosts” file where we will write the connection data of our servers.

# Hosts
manager ansible_host=107.23.74.224 ansible_ssh_user=centos ansible_ssh_private_key_file=/home/rodrigo/Development/innuy/AnsibleSwarm/ansible/private/DockerSwarm.pem
worker1 ansible_host=34.205.4.171 ansible_ssh_user=centos ansible_ssh_private_key_file=/home/rodrigo/Development/innuy/AnsibleSwarm/ansible/private/DockerSwarm.pem
[swarm-managers]manager

[swarm-workers]worker1

[swarm:children]swarm-managers
swarm-workers

Here is what each of these configuration lines means:

After those, in the next lines we are creating the logical groups [swarm-managers] and [swarm-workers], which contain the servers, and then the group [swarm] which contains the groups [swarm-managers] and [swarm-workers].
 

Role for the swarm group (all the hosts)
 

1- Common role:

Create the roles folder to store all the playbooks.

Now let’s create the common and tasks directory, where we are going to have the main.yml file which has all the necessary steps for the installation.

 

These roles are going to install the packets needed to work in all the nodes (managers and workers).

Let’s create the main.yml file with our favorite editor inside the ansibleSwarm/ansible/roles/common/tasks with the following content.

—
– name: Clean yum
become: true
shell: yum clean all
tags: [common]

– name: upgrade all packages
become: true
yum: name=* state=latest
tags: [common]

– name: Disable selinux
selinux: state=disabled
become: true
tags: [common]

– name: install unzip
become: true
yum: name=unzip
tags: [common]

– name: Enable the EPEL repository definitions.
become: true
yum: pkg=epel-release
tags: [common]

– name: Install python setup tools
become: true
yum: name=python-setuptools
tags: [common]

– name: Install Pypi
become: true
easy_install: name=pip
tags: [common]

– name: install git
become: true
Yum:
name: git
state: present
tags: [common]

2- Create the docker role

Let’s create the docker role

# mkdir -p ansibleSwarm/ansible/roles/docker/tasks

 

 

This ansible role allows the installation and configuration of the last version of docker for the community edition.

 

Let’s create the main.yml with our favorite editor.

 

 

 

—
– name: Install docker-py
become: true
pip:
name: docker-py
extra_args: –ignore-installed
tags: [docker]

 

– name: Update docker repo
become: true
lineinfile:
dest: /etc/yum.repos.d/docker.repo
create: yes
line: “{{ item }}”
with_items:
– “[dockerrepo]”
– “name=Docker Repository”
– “baseurl=https://yum.dockerproject.org/repo/main/centos/7/”
– “enabled=1”
– “gpgcheck=1”
– “gpgkey=https://yum.dockerproject.org/gpg”
tags: [docker]

– name: Install Docker
become: true
yum: pkg=docker-engine state=present
tags: [docker]

– name: enable sysv dockerd service
become: true
service:
name: docker.service
enabled: yes
tags: [docker]

– name: Start service
become: true
service:
name: docker.service
state: started
tags: [docker]

 

Specific node manager packages

 

Let’s create the role docker manager.

 

 

# mkdir -p ansibleSwarm/ansible/roles/dockermanager/tasks

 

This role initializes the docker swarm cluster in the node manager, which in turn will provide us with the token that is necessary for the worker nodes.

 

Let’s create the main.yml inside this role.

 

 

—
– name: Disabling swarm
become: yes
command: docker swarm leave -f
ignore_errors: yes
tags: [dockermanager]

– name: initialize swarm cluster
become: yes
command: docker swarm init –advertise-addr={{ swarm_iface | default(‘eth0’) }}:2377
register: bootstrap_first_node
tags: [dockermanager]

 

 

Specific node worker packages

 

Let’s create the dockerworker role.

mkdir -p ansibleSwarm/ansible/roles/dockermanager/tasks

 

 

This role is going to use the token of the manager to connect and create the Docker Swarm cluster.

 

 

—
– name: leaving older swarm
command: docker swarm leave -f
become: yes
ignore_errors: yes
tags: [swarm]

– name: join nodes to manager
command: docker swarm join –token={{ tokennode }} {{ hostmanager }}
become: yes
register: swarm_join_result
failed_when: not “‘This node is already part of a swarm’ in command_result.stderr”
tags: [swarm]

 

 

Now we are creating the variables directory for this role.

 

# mkdir -p ansibleSwarm/ansible/roles/dockerworker/vars

 

Inside the vars directory, we will be creating the main.yml with the following values to obtain the token of the manager. By doing this we can then use the tokennode and hostmanager variables in the tasks folder.

 

# vars file for dockermanager
tokennode: “{{ hostvars.manager.bootstrap_first_node.stdout.split(‘n’)[5].split(‘ ‘)[5] }}”
hostmanager: “{{ hostvars.manager.bootstrap_first_node.stdout.split(‘n’)[6] }}”

 

Launching the playbook

 

Once we have all the roles we only need to create a playbook with all the roles for the execution.

 

—
– name: Install common packages
hosts: swarm
roles:
– common
– docker

– name: Configure Manager
hosts: swarm-managers
roles:
– dockermanager

– name: Configure Workers
hosts: swarm-workers
roles:
– dockerworker

 

The final step is to execute all the roles we created before.

 

 

# ansible-playbook -i inventory/hosts swarm.yml

 

 

After executing the command the output should look similar to this.

root@ip-172-31-52-216:/home/rodrigo/Development/innuy/AnsibleSwarm/ansible# ansible-playbook -i inventory/hosts swarm.yml

PLAY [Install common packages] *************************************************

TASK [setup] *******************************************************************
ok: [worker1]ok: [manager]

TASK [common : Clean yum] ******************************************************
changed: [worker1][WARNING]: Consider using yum module rather than running yum

changed: [manager]

TASK [common : upgrade all packages] *******************************************
ok: [worker1]ok: [manager]

TASK [common : Disable selinux] ************************************************
changed: [manager]changed: [worker1]

TASK [common : install unzip] **************************************************
ok: [worker1]ok: [manager]

TASK [common : Enable the EPEL repository definitions.] ************************
ok: [worker1]ok: [manager]

TASK [common : Install python setup tools] *************************************
ok: [worker1]ok: [manager]

TASK [common : Install Pypi] ***************************************************
ok: [worker1]ok: [manager]

TASK [common : install git] ****************************************************
ok: [worker1]ok: [manager]

TASK [docker : Install docker-py] **********************************************
changed: [worker1]changed: [manager]

TASK [docker : Update docker repo] *********************************************
ok: [worker1] => (item=[dockerrepo])
ok: [manager] => (item=[dockerrepo])
ok: [worker1] => (item=name=Docker Repository)
ok: [manager] => (item=name=Docker Repository)
ok: [worker1] => (item=baseurl=https://yum.dockerproject.org/repo/main/centos/7/)
ok: [manager] => (item=baseurl=https://yum.dockerproject.org/repo/main/centos/7/)
ok: [manager] => (item=enabled=1)
ok: [worker1] => (item=enabled=1)
ok: [manager] => (item=gpgcheck=1)
ok: [worker1] => (item=gpgcheck=1)
ok: [manager] => (item=gpgkey=https://yum.dockerproject.org/gpg)
ok: [worker1] => (item=gpgkey=https://yum.dockerproject.org/gpg)

TASK [docker : Install Docker] *************************************************
ok: [manager]ok: [worker1]

TASK [docker : enable sysv dockerd service] ************************************
ok: [worker1]ok: [manager]

TASK [docker : Start service] **************************************************
ok: [manager]ok: [worker1]

PLAY [Configure Manager] *******************************************************

TASK [setup] *******************************************************************
ok: [manager]

TASK [dockermanager : Disabling swarm] *****************************************
changed: [manager]

TASK [dockermanager : initialize swarm cluster] ********************************
changed: [manager]

PLAY [Configure Workers] *******************************************************

TASK [setup] *******************************************************************
ok: [worker1]

TASK [dockerworker : leaving older swarm] **************************************
changed: [worker1]

TASK [dockerworker : join nodes to manager] ************************************
changed: [worker1]

PLAY RECAP *********************************************************************
manager : ok=17 changed=5 unreachable=0 failed=0
worker1 : ok=17 changed=5 unreachable=0 failed=0

Hope this tutorial has helped you in combining Ansible and Docker Swarm for your needs!