> For the complete documentation index, see [llms.txt](https://azutopia.gitbook.io/azu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://azutopia.gitbook.io/azu/api-reference/core.md).

# Core Module

The `Azu` module is the main entry point for creating Azu applications.

## Including Azu

```crystal
module MyApp
  include Azu
end
```

## Configuration

### configure

Configure application settings.

```crystal
Azu.configure do |config|
  config.port = 8080
  config.host = "0.0.0.0"
  config.env = Environment::Production
  config.template_hot_reload = false
end
```

### Configuration Options

| Option                | Type            | Default       | Description                |
| --------------------- | --------------- | ------------- | -------------------------- |
| `port`                | `Int32`         | `4000`        | HTTP server port           |
| `host`                | `String`        | `"0.0.0.0"`   | Bind address               |
| `env`                 | `Environment`   | `Development` | Environment mode           |
| `template_hot_reload` | `Bool`          | `true`        | Reload templates on change |
| `log`                 | `Log::Severity` | `Debug`       | Log level                  |
| `cache`               | `Cache::Store`  | `MemoryStore` | Cache backend              |

## Environment

```crystal
enum Environment
  Development
  Test
  Production
end
```

### Checking Environment

```crystal
if Azu.env.production?
  # Production-only code
end

Azu.env.development?  # => Bool
Azu.env.test?         # => Bool
```

## Starting the Application

### start

Start the HTTP server with handlers.

```crystal
MyApp.start [
  Azu::Handler::Rescuer.new,
  Azu::Handler::Logger.new,
  MyEndpoint.new,
]
```

**Parameters:**

* `handlers : Array(HTTP::Handler)` - Handler chain

### start (block)

Start with a block for additional setup.

```crystal
MyApp.start do |server|
  server.bind_tcp("0.0.0.0", 8080)
  server.listen
end
```

## Cache Access

### cache

Access the configured cache store.

```crystal
Azu.cache.set("key", "value", expires_in: 1.hour)
Azu.cache.get("key")  # => "value"
Azu.cache.delete("key")
```

## Router Access

### router

Access the application router.

```crystal
Azu.router.routes  # => Array of registered routes
```

## Logging

### log

Access the application logger.

```crystal
Azu.log.info { "Application started" }
Azu.log.error(exception: ex) { "Error occurred" }
```

## Type Aliases

```crystal
alias EmptyRequest = Azu::Request::Empty
alias Params = Hash(String, String)
```

## Constants

```crystal
VERSION = "0.5.28"
```

## See Also

* [Endpoint Reference](/azu/api-reference/endpoint.md)
* [Handler Reference](/azu/handlers/built-in.md)
* [Configuration Reference](/azu/configuration/options.md)


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