Incorta-DevOps-Task

• Track resource utilization over time. It’s required to have a script to automatically record system resources utilization on a Linux machine. The scipt creates 3 CSV files for (CPU - Memory Usage - Disk space usage) under /opt/ directory.

• Using Ansible to do the following (Deploy and schedule the above script - Install some Linux packages passed as parameters - Install Java OpenJDK 11)

Table of contents

• Getting Started
  • Prerequisites
• Requirement 1: "Record system resources utilization"
• Requirement 2: "Using Ansible configuration tool"
  • Deploy and Schedule Script
  • Install Linux packages passed as parameters
  • Install Java OpenJDK 11 on Linux environment
• Summary
• Future work: Visualize system utilization

Getting Started

These tasks are done on a local host for development and testing using Linux distribution (Ubuntu 18.04 or CentOS 7)

Prerequisites

As we will see in the second requirement, all the prerequisites will be installed for hosts via Ansible playbooks.

Packages on linux distribution:

• python3
• python3-venv
• ansible

Python packages on your python virtual environment:

• psutil : To retrieve information on system utilization

Requirement 1: "Record system resources utilization"

Python script util.py to automatically record system resources utilization on a Linux machine using psutil python package

Exact steps of the script are the following:

1. Import necessary libraries ( psutil - datetime - csv )
2. Get CPU utilization as percentage in the current time.
3. Save and append results from "Step 2" as a csv file in /opt/ directory every time the script is run.
4. Repeat "Steps 2 & 3" to get free memory & free disk spaces as percentages.

Example: Getting percentages of used virtual memory in MEM.csv with the corresponding timestamp

# psutil.virtual_memory().percent: returns the percentage of used memory
mem_free_per = round((100 - psutil.virtual_memory().percent),2)

mem_csvRow = [dt.datetime.now(),mem_free_per]
mem_csv = "/opt/MEM.csv"

# Appending results in the csv file
with open(mem_csv, "a", newline='') as fp:
    wr = csv.writer(fp, dialect='excel')
    wr.writerow(mem_csvRow)

Output sample for MEM.csv:

2020-12-08 00:35:02.228761,29.0
2020-12-08 00:36:02.368104,29.7

Requirement 2: "Using Ansible configuration tool"

Deploy and Schedule Script

Deploy and schedule "util.py" python script to run every 15 minutes using Ansible configuration management tool

Approach: Create a project specific Python Virtual Environment with only the required python packages. The script is run on the virtual environment, scheduled and deployed using Ansible playbooks.

Exact steps:

• Install and create a python 3 virtual environment named "py_venv" on etc/ansible directory via "setup_venv.yml" playbook ( apt is replaced with yum in case of using CentOs 7 )

## setup_venv.yml
  - name: Install the venv library
    command: apt install python3-venv

  - name: Create python virtual environment on Ansible directory
    command: python3 -m venv /etc/ansible/py_venv

• Activate the virtual the created environment "py_venv" using the command:

source py_venv/bin/activate

• Install any needed python libraries such as psutil on the installed virtual environment via "venv_packages.yml" playbook

## venv_packages.yml
  - name: Install psutil on virtual environment
    pip:
      name: psutil
      virtualenv: /etc/ansible/py_venv

Note: Although Virtual environment benefit is not clear here. However, in real projects it is used instead of local environments to help keep dependencies required by different projects separate by creating isolated python virtual environments for them (specially for site-packages)

• Clone the script from a public GitHub repo that acts as a server/master to a local directory with Git Ansible module via “clone_script” playbook.

## clone_script.yml
  vars:
    username: eslamwael
    repo_name: Linux-untilization-Python-script

  tasks:
  - name: Download python script from Git
    git:
      repo: https://github.com/{{ username }}/{{ repo_name }}.git
      dest: /etc/ansible/playbooks/Python_script/

Note: the benefit of using Git module that it gets the latest commit every time the task runs.

• Start cron scheduler then run the script on the virtual environment every 15 minutes via “schedule_script_venv” playbook, cron logs are saved in the /opt directory in case of scheduling errors

## schedule_script_venv.yml
  - name: Start cron scheduler service
    service:
      name: cron
      state: started

  - name: Run script every 15 minutes
    cron:
      name: "schedule script"
      minute: "*/15"
      job: Python_virtual_env_path script.py >> /opt/cron.log 2>&1

Note that Cron Ansible module allows you to create named crontab entries automatically via cron jobs in the playbooks as follows:

*/15 * * * * /etc/ansible/py_venv/bin/python3 /etc/ansible/playbooks/Python_script/util.py >> /opt/cron.log 2>&1

• Master may need to shut down the scheduler for some or all hosts, so additional playbook "stop_scheduler" is added to stop the cron scheduler from running

## stop_scheduler.yml
  - name: Stop cron scheduler service
    service:
      name: cron
      state: stopped

Install Linux packages passed as parameters

• Use Ansible playbook variables to take linux package name as an argument, then install it on "linux_package.yml" playbook using Ansible built-in packages manager such as apt module in case of Ubuntu or yum module in case of CentOS

## linux_package.yml
  vars:
    package: "{{ pkg }}"

  tasks:

  - name: Install Linux Package
    apt:
      name: "{{ package }}"

• Running "linux_package" playbook and taking linux package name "apache2 in this example" as an extra argument

sudo ansible-playbook packages_playbook.yml --extra-vars "pkg=apache2"

Install Java OpenJDK 11 on Linux environment

• Install Java OpenJDK using ansible playbook "openjdk11_install.yml" by using apt module (Ubuntu) or yum module (CentOs)

## openjdk11_install.yml
  tasks:

  - name: Install Java OpenJDK 11
    apt:
      name: openjdk-11-jdk
      update_cache: yes

Summary

File	Functionality
util.py	Python script to get information on Cpu, memory and disk utilization and save them in a Csv files under /opt
setup_venv.yml	Ansible playbook to install venv library and setup python 3 virtual environment
venv_packages.yml	Ansible playbook to install any needed python package for the project such as psutil
clone_script.yml	Ansible playbook to download the python script "util.py" from a github repo, run again for new commits
schedule_script_ven.yml	Ansible playbook to start cron scheduler and run the python script every 15 minutes
stop_schedule.yml	Ansible playbook to stop cron scheduler from running the script
linux_package.yml	Ansible playbook to install a linux package by taking the package name as an argument
openjdk11_install.yml	Ansible playbook to install Java Open Jdk 11 on linux environment

Future work: Visualize system utilization

• Creating a python script with a visualization library such as matplotlib or plotly to create a static interactive graphs for CPU, memory and disk usages over time.
• This can be done by importing the three generated CSV files in from /opt directory

Thank you