Rocket/site/guide/9-configuration.md

# Configuration

Rocket's configuration system is flexible. Based on [Figment](@figment), it
allows you to configure your application the way _you_ want while also providing
with a sensible set of defaults.

## Overview

Rocket's configuration system is based on Figment's [`Provider`]s, types which
provide configuration data. Rocket's [`Config`] and [`Config::figment()`], as
well as Figment's [`Toml`] and [`Json`], are some examples of providers.
Providers can be combined into a single [`Figment`] provider from which any
configuration structure that implements [`Deserialize`] can be extracted.

Rocket expects to be able to extract a [`Config`] structure from the provider it
is configured with. This means that no matter which configuration provider
Rocket is asked to use, it must be able to read the following configuration
values:

| key            | kind            | description                                     | debug/release default |
|----------------|-----------------|-------------------------------------------------|-----------------------|
| `address`      | `IpAddr`        | IP address to serve on                          | `127.0.0.1`           |
| `port`         | `u16`           | Port to serve on.                               | `8000`                |
| `workers`      | `usize`         | Number of threads to use for executing futures. | cpu core count        |
| `keep_alive`   | `u32`           | Keep-alive timeout seconds; disabled when `0`.  | `5`                   |
| `log_level`    | `LogLevel`      | Max level to log. (off/normal/debug/critical)   | `normal`/`critical`   |
| `cli_colors`   | `bool`          | Whether to use colors and emoji when logging.   | `true`                |
| `secret_key`   | `SecretKey`     | Secret key for signing and encrypting values.   | `None`                |
| `tls`          | `TlsConfig`     | TLS configuration, if any.                      | `None`                |
| `tls.key`      | `&[u8]`/`&Path` | Path/bytes to DER-encoded ASN.1 PKCS#1/#8 key.  |                       |
| `tls.certs`    | `&[u8]`/`&Path` | Path/bytes to DER-encoded X.509 TLS cert chain. |                       |
| `limits`       | `Limits`        | Streaming read size limits.                     | [`Limits::default()`] |
| `limits.$name` | `&str`/`uint`   | Read limit for `$name`.                         | forms = "32KiB"       |
| `ctrlc`        | `bool`          | Whether `ctrl-c` initiates a server shutdown.   | `true`                |

### Profiles

Configurations can be arbitrarily namespaced by [`Profile`]s. Rocket's
[`Config`] and [`Config::figment()`] providers automatically set the
configuration profile to "debug" when compiled in "debug" mode and "release"
when compiled in release mode. With the exception of `log_level`, which changes
from `normal` in debug to `critical` in release, all of the default
configuration values are the same in all profiles. What's more, all
configuration values _have_ defaults, so no configuration needs to be supplied
to get an application going.

In addition to any profiles you declare, there are two meta-profiles, `default`
and `global`, which can be used to provide values that apply to _all_ profiles.
Values provided in a `default` profile are used as fall-back values when the
selected profile doesn't contain a requested values, while values in the
`global` profile supplant any values with the same name in any profile.

[`Provider`]: @figment/trait.Provider.html
[`Profile`]: @figment/struct.Profile.html
[`Config`]: @api/rocket/struct.Config.html
[`Config::figment()`]: @api/rocket/struct.Config.html#method.figment
[`Toml`]: @figment/providers/struct.Toml.html
[`Json`]: @figment/providers/struct.Json.html
[`Figment`]: @api/rocket/struct.Figment.html
[`Deserialize`]: @serde/trait.Deserialize.html
[`Limits::default()`]: @api/rocket/data/struct.Limits.html#impl-Default

### Secret Key

The `secret_key` parameter configures a cryptographic key to use when encrypting
application values. In particular, the key is used to encrypt [private cookies],
which are available only when the `secrets` crate feature is enabled.

When compiled in debug mode, a fresh key is generated automatically. In release
mode, Rocket requires you to set a secret key if the `secrets` feature is
enabled. Failure to do so results in a hard error at launch time. The value of
the parameter may either be a 256-bit base64 or hex string or a slice of 32
bytes.

[private cookies]: ../requests/#private-cookies

### Limits

The `limits` parameter configures the maximum amount of data Rocket will accept
for a given data type. The value is expected to be a dictionary table where each
key corresponds to a data type and each value corresponds to the maximum size in
bytes Rocket should accept for that type. Rocket can parse both integers
(`32768`) or SI unit based strings (`"32KiB"`) as limits.

By default, Rocket specifies a `32 KiB` limit for incoming forms. Since Rocket
requires specifying a read limit whenever data is read, external data guards may
also choose to have a configure limit via the `limits` parameter. The
[`rocket_contrib::Json`] type, for instance, uses the `limits.json` parameter.

[`rocket_contrib::Json`]: @api/rocket_contrib/json/struct.Json.html

### TLS

Rocket includes built-in, native support for TLS >= 1.2 (Transport Layer
Security). In order for TLS support to be enabled, Rocket must be compiled with
the `"tls"` feature:

```toml
[dependencies]
rocket = { version = "0.5.0-dev", features = ["tls"] }
```

TLS is configured through the `tls` configuration parameter. The value of `tls`
is a dictionary with two keys: `certs` and `key`, described in the table above.
Each key's value may be either a path to a file or raw bytes corresponding to
the expected value. When a path is configured in a file source, such as
`Rocket.toml`, relative paths are interpreted as being relative to the source
file's directory.

! warning: Rocket's built-in TLS implements only TLS 1.2 and 1.3. As such, it
  may not be suitable for production use.

### Workers

The `workers` parameter sets the number of threads used for parallel task
execution; there is no limit to the number of concurrent tasks. Due to a
limitation in upstream async executers, unlike other values, the `workers`
configuration value cannot be reconfigured or be configured from sources other
than those provided by [`Config::figment()`], detailed below. In other words,
only the values set by the `ROCKET_WORKERS` environment variable or in the
`workers` property of `Rocket.toml` will be considered - all other `workers`
values are ignored.

## Default Provider

Rocket's default configuration provider is [`Config::figment()`]; this is the
provider that's used when calling [`rocket::build()`].

The default figment merges, at a per-key level, and reads from the following
sources, in ascending priority order:

  1. [`Config::default()`] - which provides default values for all parameters.
  2. `Rocket.toml` _or_ TOML file path in `ROCKET_CONFIG` environment variable.
  3. `ROCKET_` prefixed environment variables.

The selected profile is the value of the `ROCKET_PROFILE` environment variable,
or if it is not set, "debug" when compiled in debug mode and "release" when
compiled in release mode.

As a result, without any effort, Rocket's server can be configured via a
`Rocket.toml` file and/or via environment variables, the latter of which take
precedence over the former. Note that neither the file nor any environment
variables need to be present as [`Config::default()`] is a complete
configuration source.

[`Config::default()`]: @api/rocket/struct.Config.html#method.default

### Rocket.toml

Rocket searches for `Rocket.toml` or the filename in a `ROCKET_CONFIG`
environment variable starting at the current working directory. If it is not
found, the parent directory, its parent, and so on, are searched until the file
is found or the root is reached. If the path set in `ROCKET_CONFIG` is absolute,
no such search occurs, and the set path is used directly.

The file is assumed to be _nested_, so each top-level key declares a profile and
its values the value for the profile. The following is an example of what such a
file might look like:

```toml
## defaults for _all_ profiles
[default]
address = "0.0.0.0"
limits = { forms = "64 kB", json = "1 MiB" }

## set only when compiled in debug mode, i.e, `cargo build`
[debug]
port = 8000
## only the `json` key from `default` will be overridden; `forms` will remain
limits = { json = "10MiB" }

## set only when the `nyc` profile is selected
[nyc]
port = 9001

## set only when compiled in release mode, i.e, `cargo build --release`
## don't use this secret_key! generate your own and keep it private!
[release]
port = 9999
secret_key = "hPRYyVRiMyxpw5sBB1XeCMN1kFsDCqKvBi2QJxBVHQk="
```

### Environment Variables

Rocket reads all environment variable names prefixed with `ROCKET_` using the
string after the `_` as the name of a configuration value as the value of the
parameter as the value itself. Environment variables take precedence over values
in `Rocket.toml`. Values are parsed as loose form of TOML syntax. Consider the
following examples:

```sh
ROCKET_INTEGER=1
ROCKET_FLOAT=3.14
ROCKET_STRING=Hello
ROCKET_STRING="Hello"
ROCKET_BOOL=true
ROCKET_ARRAY=[1,"b",3.14]
ROCKET_DICT={key="abc",val=123}
```

## Extracting Values

Your application can extract any configuration that implements [`Deserialize`]
from the configured provider, which is exposed via [`Rocket::figment()`]:

```rust
# #[macro_use] extern crate rocket;
# extern crate serde;

use serde::Deserialize;


#[launch]
fn rocket() -> _ {
    let rocket = rocket::build();
    let figment = rocket.figment();

    #[derive(Deserialize)]
    struct Config {
        port: u16,
        custom: Vec<String>,
    }

    // extract the entire config any `Deserialize` value
    let config: Config = figment.extract().expect("config");

    // or a piece of it into any `Deserialize` value
    let custom: Vec<String> = figment.extract_inner("custom").expect("custom");

    rocket
}
```

Both values recognized by Rocket and values _not_ recognized by Rocket can be
extracted. This means you can configure values recognized by your application in
Rocket's configuration sources directly. The next section describes how you can
customize configuration sources by supplying your own `Provider`.

Because it is common to store configuration in managed state, Rocket provides an
`AdHoc` fairing that 1) extracts a configuration from the configured provider,
2) pretty prints any errors, and 3) stores the value in managed state:

```rust
# #[macro_use] extern crate rocket;
# extern crate serde;
# use serde::Deserialize;
# #[derive(Deserialize)]
# struct Config {
#     port: u16,
#     custom: Vec<String>,
# }

use rocket::{State, fairing::AdHoc};

#[get("/custom")]
fn custom(config: &State<Config>) -> String {
    config.custom.get(0).cloned().unwrap_or("default".into())
}

#[launch]
fn rocket() -> _ {
    rocket::build()
        .mount("/", routes![custom])
        .attach(AdHoc::config::<Config>())
}
```

[`Rocket::figment()`]: @api/rocket/struct.Rocket.html#method.figment

## Custom Providers

A custom provider can be set via [`rocket::custom()`], which replaces calls to
[`rocket::build()`]. The configured provider can be built on top of
[`Config::figment()`], [`Config::default()`], both, or neither. The
[Figment](@figment) documentation has full details on instantiating existing
providers like [`Toml`] and [`Json`] as well as creating custom providers for
more complex cases.

! note: You may need to depend on `figment` and `serde` directly.

  Rocket reexports `figment` from its crate root, so you can refer to `figment`
  types via `rocket::figment`. However, Rocket does not enable all features from
  the figment crate. As such, you may need to import `figment` directly:

  `
  figment = { version = "0.9", features = ["env", "toml", "json"] }
  `

  Furthermore, you should directly depend on `serde` when using its `derive`
  feature, which is also not enabled by Rocket:

  `
  serde = { version = "1", features = ["derive"] }
  `

As a first example, we override configuration values at runtime by merging
figment's tuple providers with Rocket's default provider:

```rust
# #[macro_use] extern crate rocket;

use rocket::data::{Limits, ToByteUnit};

#[launch]
fn rocket() -> _ {
    let figment = rocket::Config::figment()
        .merge(("port", 1111))
        .merge(("limits", Limits::new().limit("json", 2.mebibytes())));

    rocket::custom(figment).mount("/", routes![/* .. */])
}
```

More involved, consider an application that wants to use Rocket's defaults for
[`Config`], but not its configuration sources, while allowing the application to
be configured via an `App.toml` file that uses top-level keys as profiles
(`.nested()`), `APP_` environment variables as global overrides (`.global()`),
and `APP_PROFILE` to configure the selected profile:

```rust
# #[macro_use] extern crate rocket;

use serde::{Serialize, Deserialize};
use figment::{Figment, Profile, providers::{Format, Toml, Serialized, Env}};
use rocket::fairing::AdHoc;

#[derive(Debug, Deserialize, Serialize)]
struct Config {
    app_value: usize,
    /* and so on.. */
}

impl Default for Config {
    fn default() -> Config {
        Config { app_value: 3, }
    }
}

#[launch]
fn rocket() -> _ {
    let figment = Figment::from(rocket::Config::default())
        .merge(Serialized::defaults(Config::default()))
        .merge(Toml::file("App.toml").nested())
        .merge(Env::prefixed("APP_").global())
        .select(Profile::from_env_or("APP_PROFILE", "default"));

    rocket::custom(figment)
        .mount("/", routes![/* .. */])
        .attach(AdHoc::config::<Config>())
}
```

Rocket will extract it's configuration from the configured provider. This means
that if values like `port` and `address` are configured in `Config`, `App.toml`
or `APP_` environment variables, Rocket will make use of them. The application
can also extract its configuration, done here via the `Adhoc::config()` fairing.

[`rocket::custom()`]: @api/rocket/fn.custom.html
[`rocket::build()`]: @api/rocket/fn.custom.html