title	published	description	tags	cover_image	canonical_url	id
#90DaysOfDevOps - Tags, Variables, Inventory & Database Server config - Day 68	false	90DaysOfDevOps - Tags, Variables, Inventory & Database Server config	devops, 90daysofdevops, learning			1048780

Tags, Variables, Inventory & Database Server config

Variables

There are two main types of variables within Ansible.

User created
Ansible Facts

Ansible Facts

Each time we have run our playbooks, we have had a task that we have not defined called "Gathering facts" we can use these variables or facts to make things happen with our automation tasks.

If we were to run the following ansible proxy -m setup command we should see a lot of output in JSON format. There is going to be a lot of information on your terminal though to use this so we would like to output this to a file using ansible proxy -m setup >> facts.json you can see this file in this repository, ansible-scenario5

If you open this file you can see all sorts of information for our command. We can get our IP addresses, architecture, and bios version. A lot of useful information if we want to leverage this and use this in our playbooks.

An idea would be to potentially use one of these variables within our nginx template mysite.j2 where we hard-coded the IP addresses of our webservers. You can do this by creating a for loop in your mysite.j2 and this is going to cycle through the group [webservers] this enables us to have more than our 2 webservers automatically and dynamically created or added to this load balancer configuration.

#Dynamic Config for server {{ ansible_facts['nodename'] }}
    upstream webservers {
  {% for host in groups['webservers'] %}
        server {{ hostvars[host]['ansible_facts']['nodename'] }}:8000;
    {% endfor %}
    }

    server {
        listen 80;

        location / {
                proxy_pass http://webservers;
        }
    }

The outcome of the above will look the same as it does right now but if we added more web servers or removed one this would dynamically change the proxy configuration. For this to work you will need to have name resolution configured.

User created

User-created variables are what we have created ourselves. If you take a look in our playbook you will see we have vars: and then a list of 3 variables we are using there.

- hosts: webservers
  become: yes
  vars:
    http_port: 8000
    https_port: 4443
    html_welcome_msg: "Hello 90DaysOfDevOps - Welcome to Day 68!"
  roles:
    - common
    - apache2
  tags: web

- hosts: proxy
  become: yes
  roles:
    - common
    - nginx
  tags: proxy

We can however keep our playbook clear of variables by moving them to their file. We are going to do this but we will move into the ansible-scenario6 folder. In the root of that folder, we are going to create a group_vars folder. We are then going to create another folder called all (all groups are going to get these variables). In there we will create a file called common_variables.yml and we will copy our variables from our playbook into this file. Removing them from the playbook along with vars: as well.

http_port: 8000
https_port: 4443
html_welcome_msg: "Hello 90DaysOfDevOps - Welcome to Day 68!"

Because we are associating this as a global variable we could also add in our NTP and DNS servers here as well. The variables are set from the folder structure that we have created. You can see below how clean our Playbook now looks.

- hosts: webservers
  become: yes
  roles:
    - common
    - apache2
  tags: web

- hosts: proxy
  become: yes
  roles:
    - common
    - nginx
  tags: proxy

One of those variables was the http_port, we can use this again in our for loop within the mysite.j2 as per below:

#Dynamic Config for server {{ ansible_facts['nodename'] }}
    upstream webservers {
  {% for host in groups['webservers'] %}
        server {{ hostvars[host]['ansible_facts']['nodename'] }}:{{ http_port }};
    {% endfor %}
    }

    server {
        listen 80;

        location / {
                proxy_pass http://webservers;
        }
    }

We can also define an ansible fact in our roles/apache2/templates/index.HTML.j2 file so that we can understand which webserver we are on.

<html>

<h1>{{ html_welcome_msg }}! I'm webserver {{ ansible_facts['nodename'] }} </h1>

</html>

The results of running the ansible-playbook playbook6.yml command with our variable changes mean that when we hit our loadbalancer you can see that we hit either of the webservers we have in our group.

We could also add a folder called host_vars and create a web01.yml and have a specific message or change what that looks like on a per host basis if we wish.

Inventory Files

So far we have used the default hosts file in the /etc/ansible folder to determine our hosts. We could however have different files for different environments, for example, production and staging. I am not going to create more environments. But we can create our host files.

We can create multiple files for our different inventory of servers and nodes. We would call these using ansible-playbook -i dev playbook.yml you can also define variables within your host's file and then print that out or leverage that variable somewhere else in your playbooks for example in the example and training course I am following along to below they have added the environment variable created in the host file to the loadbalancer web page template to show the environment as part of the web page message.

Deploying our Database server

We still have one more machine we have not powered up yet and configured. We can do this using vagrant up db01 from where our Vagrantfile is located. When this is up and accessible we then need to make sure the SSH key is copied over using ssh-copy-id db01 so that we can access it.

We are going to be working from the ansible-scenario7 folder

Let's then use ansible-galaxy init roles/mysql to create a new folder structure for a new role called "MySQL"

In our playbook, we are going to add a new play block for the database configuration. We have our group database defined in our /etc/ansible/hosts file. We then instruct our database group to have the role common and a new role called MySQL which we created in the previous step. We are also tagging our database group with the database, this means as we discussed earlier we can choose to only run against these tags if we wish.

- hosts: webservers
  become: yes
  roles:
    - common
    - apache2
  tags:
    web

- hosts: proxy
  become: yes
  roles:
    - common
    - nginx
  tags:
    proxy

- hosts: database
  become: yes
  roles:
    - common
    - mysql
  tags: database

Within our roles folder structure, you will now have the tree automatically created, we need to populate the following:

Handlers - main.yml

# handlers file for roles/mysql
- name: restart mysql
  service:
    name: mysql
    state: restarted

Tasks - install_mysql.yml, main.yml & setup_mysql.yml

install_mysql.yml - this task is going to be there to install MySQL and ensure that the service is running.

- name: "Install Common packages"
  apt: name={{ item }} state=latest
  with_items:
   - python3-pip
   - mysql-client
   - python3-mysqldb
   - libmysqlclient-dev

- name: Ensure mysql-server is installed latest version
  apt: name=mysql-server state=latest

- name: Installing python module MySQL-python
  pip:
    name: PyMySQL

- name: Ensure mysql-server is running
  service:
    name: mysql
    state: started

main.yml is a pointer file that will suggest that we import_tasks from these files.

# tasks file for roles/mysql
- import_tasks: install_mysql.yml
- import_tasks: setup_mysql.yml

setup_mysql.yml - This task will create our database and database user.

- name: Create my.cnf configuration file
  template: src=templates/my.cnf.j2 dest=/etc/mysql/conf.d/mysql.cnf
  notify: restart mysql

- name: Create database user with name 'devops' and password 'DevOps90' with all database privileges
  community.mysql.mysql_user:
    login_unix_socket: /var/run/mysqld/mysqld.sock
    login_user: "{{ mysql_user_name }}"
    login_password: "{{ mysql_user_password }}"
    name: "{{db_user}}"
    password: "{{db_pass}}"
    priv: '*.*:ALL'
    host: '%'
    state: present

- name: Create a new database with name '90daysofdevops'
  mysql_db:
    login_user: "{{ mysql_user_name }}"
    login_password: "{{ mysql_user_password }}"
    name: "{{ db_name }}"
    state: present

You can see from the above we are using some variables to determine some of our configuration such as passwords, usernames and databases, this is all stored in our group_vars/all/common_variables.yml file.

http_port: 8000
https_port: 4443
html_welcome_msg: "Hello 90DaysOfDevOps - Welcome to Day 68!"

mysql_user_name: root
mysql_user_password: "vagrant"
db_user: devops
db_pass: DevOps90
db_name: 90DaysOfDevOps

We also have my.cnf.j2 file in the templates folder, which looks like below:

[mysql]
bind-address = 0.0.0.0

Running the playbook

Now we have our VM up and running and we have our configuration files in place, we are now ready to run our playbook which will include everything we have done before if we run the following ansible-playbook playbook7.yml or we could choose to just deploy to our database group with the ansible-playbook playbook7.yml --tags database command, which will just run our new configuration files.

I ran only against the database tag but I stumbled across an error. This error tells me that we do not have pip3 (Python) installed. We can fix this by adding this to our common tasks and install

We fixed the above and ran the playbook again and we have a successful change.

We should probably make sure that everything is how we want it to be on our newly configured db01 server. We can do this from our control node using the ssh db01 command.

To connect to MySQL I used sudo /usr/bin/mysql -u root -p and gave the vagrant password for root at the prompt.

When we have connected let's first make sure we have our user created called DevOps. select user, host from mysql.user;

Now we can issue the SHOW DATABASES; command to see our new database that has also been created.

I used the root to connect but we could also now log in with our DevOps account, in the same way, using sudo /usr/bin/MySQL -u devops -p but the password here is DevOps90.

One thing I have found is that in our setup_mysql.yml I had to add the line login_unix_socket: /var/run/mysqld/mysqld.sock to successfully connect to my db01 MySQL instance and now every time I run this it reports a change when creating the user, any suggestions would be greatly appreciated.

Resources

What is Ansible
Ansible 101 - Episode 1 - Introduction to Ansible
NetworkChuck - You need to learn Ansible right now!
Your complete guide to Ansible

This final playlist listed above is where a lot of the code and ideas came from for this section, a great resource and walkthrough in video format.

See you on Day 69

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Tags, Variables, Inventory & Database Server config

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Tags, Variables, Inventory & Database Server config

Tags

Variables

Ansible Facts

User created

Inventory Files

Deploying our Database server

Running the playbook

Resources