A connection pool is a managed collection of reusable database connections shared across clients or execution threads. In an asynchronous Rust web service, sqlx creates the pool and application state makes it available to handlers. section 4.0 section 4.3.2
A typical Actix Web integration follows this request-to-database path:
- Read DATABASE_URL and create a PgPool during application startup. section 4.3.3
- Store the pool in AppState and inject that state into the web application. section 4.3.2 section 4.3.3
- Access the injected pool in a handler and pass it to database-access functions. section 4.5
- Construct and execute SQL queries through the pool rather than opening a separate connection for each operation. section 4.5
Tutor web service
A database-backed tutor service creates a sqlx PgPool in main(), places it in AppState alongside health-check data, and exposes it to course and registration handlers. The same structure is built incrementally: first connect from vanilla Rust, then configure routes and state, then implement database operations and tests. section 4.0 section 8.1
use sqlx::postgres::PgPool;
use std::sync::Mutex;
pub struct AppState {
pub health_check_response: String,
pub visit_count: Mutex<u32>,
pub db: PgPool,
}
The AppState definition makes the pool’s ownership and application-wide availability explicit. section 4.3.2
