Aura Engine

Aura Engine is a play-out engine as part of Aura Radio Software Suite, specifically build for the requirements of community radios.

• Aura Engine
  • Features
  • Architecture
  • Requirements
  • Installation
    • Install System Libraries
    • Install Engine
    • Setup Database
    • Configuration
  • Running Engine
    • Development
    • Production
      • API Server
  • Logging
  • About
  • Resources

Features

• Play audio from multiple sources
• Dynamic switching of sources
• Record output to filesystem
• Stream output to an Icecast Server
• Multichannel Line-out
• Blank Detenction / Silence Detecter
• Auto Pilot a.k.a. Fallback Handling
• API to query Track-Service
• API to query monthly reports
• API to query data for a studio clock
• Web Application for displaying the Track-Service
• Web Application for displaying the studio clock

Read more on the Engine Features page.

Architecture

AURA Engine as part of the AURA Radio Suite uses an modulear architecture based on a REST API. All external information is retrieved using JSON data-structures.

To learn more, checkout the Engine Developer Guide or visit the Aura Meta repository.

Requirements

Hardware Requirements: This depends on how many audio sources and targets you are going to use, but for the most common scenarios any current hardware should be sufficient. For the audio devices it is required to use an interface which has supported ALSA drivers.

Operating System: Any linux system with ALSA, PulseAudio or Jack2 support should work. It is tested and coded on Debian Stretch and Ubuntu 18.0 with Python 3.6+.

Installation

git clone https://gitlab.servus.at/autoradio/engine

Install System Libraries

Aura Engine requires at least Node 13 and Python 3.7.

sudo apt install \
    git \
    supervisor \
    nodejs \
    python3.7 python3.7-pip python3.7-dev \
    redis-server \
    libsndfile1 ffmpeg \
    liquidsoap liquidsoap-plugin-icecast \
    mariadb-server libmariadbclient-dev \
    quelcom \
    liquidsoap-plugin-alsa liquidsoap-plugin-pulseaudio \
    liquidsoap-plugin-all

Install Engine

Development Environment:

sudo ./install.sh

Production Environment:

sudo ./install.sh prod

Setup Database

mysql -u root -p

CREATE DATABASE aura_engine CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;  
CREATE USER 'aura'@'localhost' IDENTIFIED BY 'secure-password';  
GRANT ALL PRIVILEGES ON aura_engine.* TO 'aura'@'localhost';  

Configuration

Run

  sh init.sh

This creates the folder /var/audio and copies some default configuration to /etc/aura/engine.ini

After that, you have to edit the settings in /etc/aura/engine.ini. Ensure to take your time to carefully review those settings!

Read more about detailed settings in the Configuration Guide.

Running Engine

Development

While developing there is a simple convencience script run.sh to get you started. Call the engine's components in following order:

    ./run.sh      # Starts the engine-core component
    ./run.sh lqs  # Starts the engine-liquidsoap component
    ./run.sh api  # Starts the engine-api component

In development mode Engine uses the Flask development server. This server should not be used in your production environment.

Production

In production the process is slightly different to ensure the engine's components are always running i.e. restart themselves after some system restart or crash. Therefore they are executed using a system service:

  systemctl start aura-engine  
  systemctl start aura-lqs

and on system boot run following:

  systemctl enable aura-engine
  systemctl enable aura-lqs

API Server

For production Engine API uses the WSGI HTTP Server Gunicorn.

In production Gunicorn is used in combination with some proxy server, such as Nginx.

Although there are many HTTP proxies available, we strongly advise that you use Nginx. If you choose another proxy server you need to make sure that it buffers slow clients when you use default Gunicorn workers. Without this buffering Gunicorn will be easily susceptible to denial-of-service attacks. You can use Hey to check if your proxy is behaving properly. — Gunicorn Docs.

Supervisor is a preferable solution to run the gunicorn server in the background and also start it automatically on reboot.

Start the API service with Supervisor

    sudo supervisorctl reread
    sudo supervisorctl update
    sudo supervisorctl avail
    sudo supervisorctl restart engine-api

In case you want to reload whole supervisor service

    sudo service supervisor restart

Logging

All Engine logs for production can be found in /var/log/aura/engine

You can access the service logs using one of:

    journalctl -u aura-lqs
    journalctl -u aura-engine

About

Aura Engine is the play-out engine of the Aura Radio Software Suite. Aura stands for Automated Radio and is a swiss army knife for community radios. Beside the Engine it provides Steering (Admin Interface for the radio station), Dashboard (Collaborative scheduling and programme coordination), Tank (Audio uploading, pre-processing and delivery). Read more in the Aura Meta repository or on the specific project pages.

Steering	Dashboard	Tank	Engine

Resources

• Python: https://docs.python.org/
• Redis: https://redis.io/
• Liquidsoap: https://www.liquidsoap.info/doc-1.4.0/
• Jack Audio: https://jackaudio.org/
• Flask: https://palletsprojects.com/p/flask/
• Supervisor: http://supervisord.org/
• Gunicorn: https://gunicorn.org/