Struct SessionPool 

pub struct SessionPool<S = SnowflakeSession> { /* private fields */ }

A bounded pool of authenticated sessions for one (account, user).

Generic over the session type for testability; the engine uses SessionPool<SnowflakeSession>.

Implementations

impl<S> SessionPool<S>

pub fn new( id: u64, key: SessionKey, max: usize, now: DateTime<Utc>, auth_gate: Arc<TokioMutex<()>>, ) -> Self

Builds an empty pool with capacity max (clamped to ≥ 1), sharing the given auth gate.

pub async fn checkout<F, Fut, E>(&self, create: F) -> Result<Checkout<S>, E>

where F: FnOnce() -> Fut, Fut: Future<Output = Result<(S, QueryContext), E>>,

Checks out a session: reuses the most-recently-returned idle one (LIFO, good temporal affinity), or creates a new one via create if none is idle and the pool is under capacity.

create returns the session and its concrete base context. It is only invoked while holding a permit with no idle session available, so the live count never exceeds max.

Errors

Propagates create’s error (e.g. authentication failure).

pub fn checkout_all_idle(&self) -> Vec<Checkout<S>>

Checks out every currently-idle session without waiting or creating.

Used by the keep-alive heartbeat: each borrowed session holds a real permit, so a concurrent checkout briefly waits for restore instead of authenticating a duplicate session (a spurious browser SSO). Busy sessions are skipped — the query path keeps them alive itself.

pub fn restore(&self, checkout: Checkout<S>)

Returns a borrowed session to its slot untouched — unlike checkin it preserves last_used and the recorded context, because a keep-alive heartbeat is not a query.

pub fn checkin(&self, checkout: Checkout<S>, current: QueryContext)

Returns a session to its slot with the context now applied to it.

pub fn start_query(&self, member_id: u64, sql: String)

Records that a checked-out member has started running sql (a truncated preview), so menus/status can show what each busy session is doing.

pub fn discard(&self, checkout: Checkout<S>)

Discards a session — e.g. after expiry — removing its slot (releases the permit and frees its capacity for a fresh auth).

pub fn touch(&self)

Records that the pool served a query.

pub fn id(&self) -> u64

The pool id.

pub fn live(&self) -> usize

The number of live sessions (idle + checked out).

pub fn info(&self) -> SessionInfo

A serializable snapshot of the pool, including each member.