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Oxicloud/doc/database-transactions.md
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Dionisio f2d35ca792 feat: auto-persist JWT secret, remove setup token requirement
- JWT secret auto-generates and persists to <STORAGE_PATH>/.jwt_secret
- Remove setup token: first admin setup is open until system initialized
- Fix schema.sql: move CREATE EXTENSION pg_trgm/ltree to top
- Update login UI and auth.js to remove setup token fields
2026-03-05 22:12:53 +01:00

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# 19 - Database Transactions
OxiCloud uses explicit transactions on PostgreSQL to guarantee data integrity. All transactional operations follow ACID properties:
- **Atomicity** -- all-or-nothing. If any part fails, the entire transaction fails.
- **Consistency** -- the database moves from one valid state to another.
- **Isolation** -- concurrent transactions behave as if sequential.
- **Durability** -- once committed, the transaction survives system failures.
## Implementation
The **with_transaction** helper wraps the standard pattern: begin, execute, commit on success, rollback on error.
### Transaction Utility
Located in `src/infrastructure/repositories/pg/transaction_utils.rs`:
```rust
/// Helper function to execute database operations in a transaction
pub async fn with_transaction<F, T, E>(
pool: &Arc<PgPool>,
operation_name: &str,
operation: F,
) -> Result<T, E>
where
F: for<'c> FnOnce(&'c mut Transaction<'_, Postgres>) -> futures::future::BoxFuture<'c, Result<T, E>>,
E: From<SqlxError> + std::fmt::Display
{ ... }
```
This function takes a connection pool and a closure with operations, handles begin/commit/rollback automatically, and provides detailed logging of the transaction lifecycle.
### Repository Usage Example
```rust
// Creación de un usuario con transacción explícita
async fn create_user(&self, user: User) -> UserRepositoryResult<User> {
with_transaction(
&self.pool,
"create_user",
|tx| {
Box::pin(async move {
// Operación principal - insertar usuario
sqlx::query("INSERT INTO auth.users ...")
.bind(...)
.execute(&mut **tx)
.await?;
// Operaciones adicionales dentro de la misma transacción
// ...
Ok(user_clone)
})
}
).await
}
```
## Use Cases
### UserPgRepository
1. **User creation** -- guarantees all insert operations are atomic. Allows related operations (like permission setup) to be bundled.
2. **User update** -- ensures modifications apply fully or not at all. Supports combined operations like profile info and preference updates.
### SessionPgRepository
1. **Session creation** -- inserts the session and updates the user's last-access timestamp in a single transaction. Keeps sessions and user data consistent.
2. **Session revocation** -- ensures revoking one or all sessions for a user is atomic. Allows logging security events within the same transaction.
## Isolation Levels
OxiCloud supports different transaction isolation levels via **with_transaction_isolation**:
```rust
// Ejemplo de uso con nivel de aislamiento específico
with_transaction_isolation(
&pool,
"operacion_critica",
sqlx::postgres::PgIsolationLevel::Serializable,
|tx| { ... }
).await
```
Available isolation levels:
1. **Read Committed** (default) -- guarantees reads see only committed data. Does not prevent non-repeatable or phantom reads.
2. **Repeatable Read** -- guarantees consistent reads throughout the transaction. Prevents non-repeatable reads but not phantom reads.
3. **Serializable** -- highest isolation level. Transactions behave as if executed serially. Can cause serialization errors that require retry.
## Best Practices
1. **Transaction duration** -- keep transactions as short as possible. Avoid long-running operations inside them.
2. **Error handling** -- errors inside a transaction trigger automatic rollback. Use proper logging to diagnose failures.
3. **Transaction boundaries** -- define clearly where transactions begin and end. Group related operations into a single transaction.
4. **Appropriate isolation** -- use the lowest isolation level that fits the use case. Consider serializable for critical operations with conflict potential.
## Benefits
- **Data integrity** -- ACID guarantees for complex operations, prevents inconsistent states.
- **Error handling** -- automatic rollback on failure, predictable behavior.
- **Safe concurrency** -- proper handling of simultaneous operations, prevents race conditions.
- **Performance** -- fewer round-trips to the database, batch operations for better efficiency.
## Performance Considerations
Transactions add some overhead. Performance can be affected by:
- Transaction duration
- Isolation level
- Number of affected records
- Lock contention