Module keys 

The configuration keys Rainier itself reads — a typed index of the tree.

Some frameworks answer “what can I configure?” with a shipped file to read through. Rainier’s answer is this module: every key the framework writes or reads, with the type stored at it.

use rainier_framework::config::Config;
use rainier_framework::keys;

let config = Config::new();
config.set(keys::APP_NAME, "My App".to_string()).unwrap();

assert_eq!(config.get(keys::APP_NAME).as_deref(), Some("My App"));

Using them is optional — every Config method still takes a &str — but it is what turns two classes of silent mistake into compile errors:

// The port is a u16, so this does not compile.
config.set(keys::SERVER_PORT, "8000").unwrap();

// Neither does a driver spelled as a string.
config.set(keys::CACHE_DRIVER, "redis").unwrap();

Reading a driver

The driver keys hold settings — closed sets with their own parser. Read them with Config::setting, which distinguishes unset (use the default) from set to nonsense (fail, and list what was expected):

use rainier_framework::cache::CacheDriver;
use rainier_framework::config::Config;
use rainier_framework::keys;

let config = Config::new();
config.set(keys::CACHE_DRIVER, CacheDriver::Redis).unwrap();

match config.setting(keys::CACHE_DRIVER).unwrap() {
    CacheDriver::Memory => { /* … */ }
    CacheDriver::Redis | CacheDriver::RedisCluster => { /* … */ }
    CacheDriver::Memcached => { /* … */ }
    CacheDriver::DynamoDb => { /* … */ }
    // A `_` arm is worth having: a driver added to the framework is a new
    // variant, and a new variant stops an exhaustive match compiling.
    other => panic!("this application does not build a {other}"),
}

Adding your own

An application declares its keys the same way, next to the section that writes them:

use rainier_framework::config::config_keys;

config_keys! {
    /// How many posts a listing shows.
    pub POSTS_PER_PAGE: u64 = "posts.per_page";
}

Constants

APP_BASE_PATH

The directory the application was started from. Set by the framework; there is no environment variable for it.

APP_CIPHER

Which encryption envelope this application writes — native or php.

APP_DEBUG

Whether a failure may show its internals to the client.

APP_ENV

Which deployment this is.

APP_NAME

The application’s display name, in page titles and mail.

APP_URL

The application’s canonical base URL, used to generate absolute links.

CACHE_DRIVER

Which cache store to build.

CACHE_MEMCACHED_URL

host:port of the Memcached server.

CACHE_PREFIX

Prepended to every cache key, so two applications can share a server.

CACHE_REDIS_URL

The Redis DSN, or a comma-separated seed list for a cluster.

DATABASE_URL

The database DSN — sqlite::memory:, mysql://…, postgres://….

KAFKA_BROADCAST_TOPIC

The topic broadcasts are published to.

KAFKA_BROKERS

The bootstrap brokers, comma-separated — kafka-1:9092,kafka-2:9092.

KAFKA_GROUP

Which set of cursors this deployment shares.

KAFKA_PASSWORD

The SASL password.

KAFKA_SASL_MECHANISM

Which SASL mechanism the username and password are for.

KAFKA_TLS

Whether to connect over TLS. Needs the kafka-tls feature.

KAFKA_TOPIC_PREFIX

Prefixes every topic this application produces to or reads from.

KAFKA_USERNAME

The SASL username, if the cluster wants one.

LOG_FORMAT

The shape of a log line — auto, pretty, compact, json.

MAIL_DRIVER

Where mail goes.

MAIL_FROM_ADDRESS

The default From address.

MAIL_FROM_NAME

The default From display name.

METRICS_ENABLED

Whether to record Prometheus metrics.

METRICS_PATH

The path the scrape endpoint is served at.

OPENAPI_ENABLED

Whether to serve the OpenAPI document.

OPENAPI_PATH

The path the document is served at.

OPENAPI_SERVER

The base URL clients should use, if the document should name one.

OPENAPI_TITLE

The info.title of the document.

OPENAPI_VERSION

The info.version of the document — your API’s version, not the framework’s.

QUEUE_DEFAULT

The queue a job goes on when it does not name one.

QUEUE_DRIVER

Where queued jobs wait.

SERVER_COMPRESSION

Whether to gzip text responses on the way out.

SERVER_HOST

The interface the HTTP server binds to.

SERVER_MAX_BODY_BYTES

The largest request body that will be buffered, in bytes.

SERVER_PORT

The port the HTTP server binds to.

SERVER_REQUEST_TIMEOUT_SECS

How long a handler may take before the request is cancelled and answered 408, in seconds. 0 turns it off.

SESSION_COOKIE

The name of the session cookie.

SESSION_DRIVER

Where session state lives.

SESSION_LIFETIME

How long a session survives without a request, in seconds.

SESSION_SECURE

Whether the session cookie is Secure. Must be true over HTTPS.

TELEMETRY_ENABLED

Whether to join and propagate W3C trace context.

TELEMETRY_ENDPOINT

The OTLP collector’s gRPC endpoint — http://localhost:4317.

TELEMETRY_SAMPLE_RATIO

What fraction of traces this service starts to record, 0.0 to 1.0.

TELEMETRY_SERVICE_NAME

What this service calls itself in a trace.