#Configuration, data, and operations modules

Boot technique modules follow one model: a module registers an interface or facade provider, applications inject it by typed or named token, and tests can replace its backend. Bundled implementations primarily serve default paths and tests. They do not automatically provide distributed production semantics.

#ACL configuration

With config, ConfigModule<T> parses an ACL document through a3s-acl and deserializes typed configuration.

use a3s_boot::ConfigModule;
use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct AppConfig {
    port: u16,
    database_url: String,
}

let module = ConfigModule::<AppConfig>::from_acl_file(
    "app-config",
    "config/production.acl",
).await?;

Modules can also use strings, default functions, environment overrides, and a validation hook that runs before registration. ACL is the A3S Agent Configuration Language. Parse it with a3s-acl, not an HCL parser.

Do not commit secrets in configuration. Inject them from the host secret manager and avoid printing complete configuration through Debug or error messages.

#Logging and health

LoggingModule exports Logger. A LogRecord has a level, target, message, and structured fields. LogSink is the output boundary. InMemoryLogSink supports assertions and NoopLogSink makes disabled logging explicit.

RequestLoggingMiddleware records request arrival. RequestLoggingInterceptor can record completion status and duration. Redact sensitive headers, queries, bodies, and tokens before they become fields.

HealthModule combines async indicators and exposes a /health JSON route by default. Any down or failed indicator produces 503. Use .without_route() to inject only HealthCheckService and let the application choose its endpoint.

Separate liveness from readiness. A liveness check should not depend on a transient external service, or an orchestrator can repeatedly restart a healthy process during a dependency outage.

#Cache

CacheModule exports Cache with a default TTL, named instances, and global exports. CacheStore is the backend contract. The bundled InMemoryCacheStore is local to the current process.

CacheInterceptor can cache HTTP responses. #[cache_key] and #[cache_ttl] provide controller or route metadata. Define invalidation, and include tenant, identity, locale, API version, and every other representation dimension in cache keys.

#Database facade

DatabaseModule provides adapter-neutral Database, DatabaseBackend, statement, row, result, and transaction contracts. The bundled InMemoryDatabaseBackend tests execution and transaction behavior.

This facade is not A3S ORM and does not bundle a production SQL driver. An application can implement the backend or inject its own A3S ORM runtime, repository, or pool as a provider. Do not downgrade a typed repository to untyped SQL strings merely to use the module system.

#Outbound HTTP

HttpModule exports HttpService with:

• Base URL, default headers, and timeout
• GET and JSON request helpers
• Named and global exports
• Async option factories
• A replaceable HttpClientBackend

A relative URL requires a configured base URL. Define timeout, retry conditions, concurrency limits, and log fields for each downstream service. Never wait without a bound or forward every inbound header automatically.

#Files, views, and compression

RequestContext is valid only inside its asynchronous invocation scope. Do not leak references into detached tasks. Copy required values into an explicit job payload when background work must continue.

#Production selection checklist

Technique modules exist to provide clear replacement boundaries. They do not make capacity, durability, or security decisions for the deployment environment.