azure-vm-status-checker

A simple Python server with authentication for retrieving whether a process is running in an Azure VM port not. If it is not, it sends a request to start the VM. Applied to a Minecraft server process, to reduce VM usage.

Suggestions or improvements to the project and its structure are welcome!

References

• DigitalOcean - How To Add Authentication to Your App with Flask-Login
• Azure docs - Automation VM Management

Prerequisites

• Azure Webhook URL (for starting the VM).

Creating the Azure Webhook

1. Create an Azure Automation account
2. Create a runbook that stops Azure VMs
   • In my case, I searched the runbook gallery and chose the Start Azure V2 VMs by the Azure team.
3. Create a webhook for the runbook with the appropriate parameters.
4. Set the AZURE_MC_START_WEBHOOK_URL variable to the runbook URL.

Installing

Flask-SQLAlchemy usage

Flask-SQLAlchemy is a package for using SQLAlchemy within a Flask application.

Adding a row to the database

Flask provides a very useful Shell utility, which let's us run Python code inside the context of the Flask app.

After making sure that the application is running using flask run, export the Flask app and attachthe Flask shell:

export FLASK_APP=app.py
flask shell

Then, add an azurestatuschekcer.models.Admin row:

from azurestatuschecker import db
from azurestatuschecker.models import Admin
from werkzeug.security import generate_password_hash

admin=Admin(username='admin', password=generate_password_hash('password', method='sha256')) # you can hash the password if you want

db.session.add(admin)
db.session.new  # verify what are the new rows
db.session.commit()

Admin.query.all() # should return the row you just inserted

# Admin.query.delete() # deletes all the rows in the Admin table and returns the number of rows deleted

Running

Before running the app, you must set some environment variables. You can do so either by exporting them or by renaming the .env-vars.example file to .env-vars and filling the value for the variables:

export AZURE_MC_START_WEBHOOK_URL=<url_to_azure_webhook>
export SERVER_IP_ADDRESS=<server_ip>

Deploying

To Heroku

To deploy the application, you must first create the Heroku Dyno and add the Heroku Postgres Add-On. Then, on the project's root directory:

heroku login
heroku git:remote -a <heroku-app-name>
git push heroku master

To add an admin credential to the database do:

heroku run bash
flask shell

And then copy the code in the "adding a row" section and exit() the Python REPL and exit the Heroku bash.

Developing

Running a development instance:

export FLASK_APP=app.py
export FLASK_ENV=development
flask run

Running PostgreSQL on Docker

To start the container:

docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d -p 5432:5432 postgres 

The container exposes the port 5432, so we connect to it (you may need to install the PSQL client):

psql -h localhost -p 5432 -U postgres

Contributors

-José Aleixo Cruz