Module diesel 

Diesel adapter — sync core fully isolated behind spawn_blocking.

The blocking rule

Classic Diesel (and its r2d2 pool) is synchronous: pool.get() can park a thread and queries block until complete. Neither may ever run on a tokio worker. This adapter ships the whole job — pool acquisition, queries, and the transaction — to the blocking thread pool as one closure, so HTTP workers are never starved:

let users = diesel_pool.run(|conn| {
    users::table.limit(10).load::<User>(conn)
}).await?;

// Whole transaction in one closure — commit on Ok, rollback on Err:
diesel_pool.transaction(|conn| {
    diesel::insert_into(notes::table).values(&new_note).execute(conn)?;
    diesel::insert_into(outbox::table).values(&event).execute(conn)
}).await?;

Because a sync transaction cannot be held across .await, #[Transactional] deliberately rejects Diesel pools (see data::tx) — DieselBlockingPool::transaction is the supported equivalent, with the same commit-on-Ok / rollback-on-Err contract enforced by Diesel itself.

Sizing invariant

Keep r2d2 pool size ≤ tokio’s blocking-thread budget (default 512); otherwise jobs queue behind thread availability instead of pool availability and the backpressure signal lands in the wrong place.

Structs

DieselBlockingPool

Cloneable (Arc-backed) handle around a Diesel r2d2 pool.

Type Aliases

DieselConn