README.md

# Aura Engine

<img src="https://gitlab.servus.at/autoradio/meta/-/raw/master/assets/images/aura-engine.png" width="250" align="right" />

Aura Engine is a scheduling and play-out engine as part of [Aura Radio Software Suite](#About), specifically built for
the requirements of community radio stations.

<!-- TOC -->

1. [Aura Engine](#aura-engine)
    1. [Functionality](#functionality)
        1. [Scheduler](#scheduler)
            1. [Versatile playlists](#versatile-playlists)
            2. [Default playlists](#default-playlists)
        2. [Heartbeat Monitoring](#heartbeat-monitoring)
        3. [Logging](#logging)
    2. [Getting started](#getting-started)
    3. [Using Docker](#using-docker)
    4. [Read more](#read-more)
    5. [About](#about)

<!-- /TOC -->

## Functionality

In conjunction with other AURA components Engine provides several features:

- **Scheduler** to automatically broadcast your radio programme (see [AURA Dashboard](https://gitlab.servus.at/aura/dashboard) for a user interface to do scheduling)
- **Analog input and outputs** provided by [Engine Core](https://gitlab.servus.at/aura/engine-core)
- **Streaming to an [Icecast](https://icecast.org/) Server including [Icy Metadata](https://cast.readme.io/docs/icy)** provided by [Engine Core](https://gitlab.servus.at/aura/engine-core)
- **Autonomous playout** by caching the schedule information pulled from [Steering](https://gitlab.servus.at/aura/steering) in a local database. This allows Engine be keep running, independently from any network or service outages. This enables the application of (*High Availability* infrastructure scenarios)[https://gitlab.servus.at/aura/meta/-/blob/master/docs/administration/installation-guide.md#high-availability].
- **Auto DJ with Silcence Detector** provided by [Engine Core](https://gitlab.servus.at/aura/engine-core)
- **Web Application for a Track Service** (see [AURA Player](https://gitlab.servus.at/aura/player))
- **Web Application providing a Studio Clock** (see [Dashboard Clock](https://gitlab.servus.at/aura/dashboard-clock))
- **Bulk and Timeslot Recorder** (*Not yet available*, this will be provided after v1.1 by a planned `engine-recorder` component)
- **API** to query Track-Service, monthly reports and information for displaying the Studio Clock (see [Engine API](https://gitlab.servus.at/aura/engine-api))

### Scheduler

Engine provide a scheduling functionality by polling external API endpoints frequently. Those API endpoints are provided by [Steering](https://gitlab.servus.at/aura/steering) to retrieve schedule information and [Tank](https://gitlab.servus.at/aura/tank) to retrieve playlist information. To define your schedule you'll also need [AURA Dashboard](https://gitlab.servus.at/aura/dashboard) which is an elegent web user interface to manage your shows, playlists and schedules.

Ideally any audio is scheduled some time before the actual, planned playout to avoid timing issues with buffering and preloading. Nonetheless, playlists can also be scheduled after a given calendar timeslot has started already. In such case the playout starts as soon it is preloaded.

If for some reason the playout is corrupted, stopped or too silent to make any sense, then this <u>triggers a fallback using the silence detector</u> (see chapter below).

> Note: If you delete any existing timeslot in Dashboard/Steering this is only reflected in Engine until the start of the scheduling window. The scheduling window is defined by the start of the timeslot minus a configured offset in seconds (compare your Engine configuration).

#### Versatile playlists

It is possible to schedules playlists with music or pre-recorded shows stored on the **file system**, via external **streams** or live from an **analog input** in the studio. All types of sources can be mixed in a single playlist.

The switching between types of audio source is handled automatically, with configured fadings applied.

> Note: Any live sources or streams not specifying a length property, are automatically expanded to the left duration of the timeslot.

#### Default playlists

While a timeslot can have a specific playlist assigned, it is also possible to define default playlists
for schedules and shows:

- **Default Schedule Playlist**: This playlist is defined on the level of some recurrence rules (*Schedule*).
    In case the timeslot doesn't have any specific playlist assigned, this playlist is broadcasted.

- **Default Show Playlist**: This playlist can be assigned to some show. If neither the specific timeslot
    playlist nor the default schedule playlist is specified the *default show playlist* is broadcasted.

If none of these playlists have been specified the *Auto DJ* feature of [Engine Core](https://gitlab.servus.at/aura/engine-core) takes over (optional).

### Heartbeat Monitoring

Instead of checking all status properties, the Heartbeat only validates the vital ones required to run the engine. If all of those are valid, a network socket request is sent to a defined server. This heartbeat is sent continuously based on the configured `heartbeat_frequency`. The service receiving this heartbeat ticks can decide what to do with that information. One scenario could be switching to another Engine instance or any other custom failover scenario. Under `contrib/heartbeat-monitor` you'll find some sample application digesting these heartbeat signals.

### Logging

All Engine logs can be found in the local `./logs` directory. Adapt the log-level within your configuration to get more or less verbose log output. Whenever the Engine's status turns into some unhealthy state, additionally this is logged to [Engine API](https://gitlab.servus.at/aura/engine-api). Also, when it returns to some valid state this is logged to the Engine API.

## Getting started

Ensure that you have also dependencies such as `steering`, `tank`, `dashboard`, `engine-core`, and `engine-api` up and running. There's a how-to in the [Meta](https://gitlab.servus.at/aura/meta) repository to get quickly started using [Docker Compose](https://docs.docker.com/compose/).

For production we recommend running Engine using Docker Compose. If you want to install for AURA development or simply prefer to run natively, check out the [Bare Metal Installation](docs/bare-metal-installation.md).

## Using Docker

If you only want to run a single Engine Docker container, you can do this in a few, simple steps.

Before getting started copy the default configuration file to `config/engine.docker.ini`:

```shell
    cp config/sample-docker.engine.ini config/docker.engine.ini
```

You'll need update a few settings:

- The password `db_pass` for the local database holding scheduling information
- The app secret `api_tank_secret` for connecting to [AURA Tank](https://gitlab.servus.at/aura/tank)
- Also check the `ENV` variables defined in the `run.sh` script.

At the moment production deployment using Docker and Docker Compose is [*work in progress*](https://gitlab.servus.at/aura/meta/-/issues/56).

If you would like to run the local codebase, starting Engine in Docker requires you to do a build first:

```shell
    ./run.sh docker:build
```

After your build has finished start the Engine with following command.

If no build is available it pulls the latest image from [Docker Hub](https://hub.docker.com/r/autoradio/engine).

```shell
    ./run.sh docker:dev
```

## Read more

- [Bare Metal Installation](docs/bare-metal-installation.md)
- [Developer Guide](docs/developer-guide.md)
- [Setting up the Audio Store [meta]](https://gitlab.servus.at/aura/meta/-/blob/master/docs/administration/setup-audio-store.md)


## About

[<img src="https://gitlab.servus.at/autoradio/meta/-/raw/master/assets/images/aura-logo.png" width="150" />](https://gitlab.servus.at/aura/meta)

Automated Radio (AURA) is a open source software suite for community radio stations. Learn more about AURA in the [Meta repository](https://gitlab.servus.at/aura/meta).

| [<img src="https://gitlab.servus.at/aura/meta/-/raw/master/assets/images/aura-steering.png" width="150" align="left" />](https://gitlab.servus.at/aura/steering)  |  [<img src="https://gitlab.servus.at/aura/meta/-/raw/master/assets/images/aura-dashboard.png" width="150" align="left" />](https://gitlab.servus.at/aura/dashboard)  |  [<img src="https://gitlab.servus.at/aura/meta/-/raw/master/assets/images/aura-tank.png" width="150" align="left" />](https://gitlab.servus.at/aura/tank) | [<img src="https://gitlab.servus.at/aura/meta/-/raw/master/assets/images/aura-engine.png" width="150" align="left" />](https://gitlab.servus.at/aura/engine)  |
|---|---|---|---|
| [Steering](https://gitlab.servus.at/aura/steering)  | [Dashboard](https://gitlab.servus.at/aura/dashboard)<br/>[Dashboard Clock](https://gitlab.servus.at/aura/dashboard-clock)  | [Tank](https://gitlab.servus.at/aura/tank)  | [Engine](https://gitlab.servus.at/aura/engine)<br/>[Engine Core](https://gitlab.servus.at/aura/engine-core)<br/>[Engine API](https://gitlab.servus.at/aura/engine-api)  |