Wednesday, November 1, 2017

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.

What is Docker Swarm?

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:

First, we are going to create the directory to store the project.

# mkdir ansibleSwarm

Now create the ansible and inventory directories.

# mkdir -p ansibleSwarm/ansible/inventory

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= ansible_ssh_user=centos ansible_ssh_private_key_file=/home/rodrigo/Development/innuy/AnsibleSwarm/ansible/private/DockerSwarm.pem worker1 ansible_host= 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:
  • manager - logical name of the server
  • ansible_host - IP or DNS name of the server
  • ansible_ssh_user - Username which ansible is going to use to connect to the server using SSH.
  • ansible_ssh_private_key_file - Path of the ssh key of the AWS server.

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.

# mkdir -p ansibleSwarm/ansible/roles

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=" - "enabled=1" - "gpgcheck=1" - "gpgkey=" 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= ok: [manager] => (item=baseurl= ok: [manager] => (item=enabled=1) ok: [worker1] => (item=enabled=1) ok: [manager] => (item=gpgcheck=1) ok: [worker1] => (item=gpgcheck=1) ok: [manager] => (item=gpgkey= ok: [worker1] => (item=gpgkey= 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!