This project is the backend part of the web service, which allows making video calls between two authorized clients. The principle of operation is similar to regular telephony: the user (caller) searches for the ID or username of the second user (callee) and then creates a call.

The backend consists of a signaling server (helper service for WebRTC) and a classic REST server for interacting with the frontend. The basic functionality of the billing system has been implemented: each user has his own virtual balance, calls are charged on the side of the caller with a per-minute payment with rounding up, upon reaching zero balance, the ability to make calls is blocked. The ability to replenish the account is carried out by payments. Authorization is implemented using the jwt token.

There is a simple example of a client that allows you to check the operation of WebRTC and the signaling server, but to implement the full functionality of the video calls web service, need to develop a client application like SPA.

Databases in the project - PostgreSQL 12.5. The backend uses the following packages:

• aiohttp for asynchronous HTTP Server;
• python-socketio for Socket.IO server(signaling server);
• sqlalchemy for working with a database;
• alembic for managing database migrations;
• asyncpg as database driver (the fastest asynchronous driver for CPython);
• aiohttp-apispec with marshmallow for describe schemas tha are used for validation, serialize/deserialize data and generation Swagger Specification;
• pytest for unit testing;
• factory-boy for generate test data in tests;
• flake8 for checking the code for errors and non-compliance with PEP8 standards;
• pip-tools for working with pip packages;
• and some others, please check out the requirements.in

Create from template and modify .env file

cp .env.example .env

Set the SYSTEM_USER variable for your user (run id -u && id -g in Unix).

To build backend and client containers and run all containers

docker-compose up -d --build

docker exec -it backend alembic upgrade head

Once deployed, you can use the basic client functionality to test the WebRTC technology. To do this, go to the link http://localhost:7000/ (where 7000 is CLIENT_PORT environment variable). You can do this on one device by opening two tabs in the browser, or by opening in different browsers (for this, it is desirable to have 2 audio/video sources), or by copying the client to another device on your local network (you do not need to run the backend there, the client application is enough) by setting the correct BACKEND_IP (IP of the first device where deployed backend) value in the environment variables.

In order to take advantage of the advantages of a swagger (such as auto-documentation and REST API client) visit the following link: http://localhost:8080/api/v1/docs/ (where 8080 is BACKEND_PORT environment variable). To use most REST API points, you need a JWT token, which can be obtained from the following API point (you must first create a user): http://localhost:8080/api/v1/auth/login/ Then you can put it in the swagger authorization interface (click the Authorize button or lock icon)

docker exec -it backend flake8

docker exec -it backend pytest -s --pdb --cov=backend --cov-report html

This cool method for testing migrations was borrowed from alvassin.

Simple and efficient method to check that migration does not have typos and rolls back all schema changes. Does not require maintenance - you can add this test to your project once and forget about it.

In particular, test detects the data types, that were previously created by upgrade() method and were not removed by downgrade(): when creating a table/column, Alembic automatically creates custom data types specified in columns (e.g. enum), but does not delete them when deleting table or column - developer has to do it manually.

Test retrieves all migrations list, and for each migration executes upgrade, downgrade, upgrade Alembic commands. See test_stairway.py for example.