Enum RecycleStrategy 

pub enum RecycleStrategy {
    SelectOne,
    Ping,
    None,
    Custom(RecycleCheck),
}

Strategy used by the async Pool to validate a connection when it is checked back out (recycled).

Defaults to SelectOne. The probe runs on every acquire after the connection’s passive liveness check; a failing probe evicts the connection and the pool transparently builds a fresh one.

Variants

SelectOne

Run an unconditional ROLLBACK round-trip on every checkout. The default — catches a half-dead connection at acquire time at the cost of one round-trip, and discharges any transaction left open by a panicked or cancelled AsyncTransaction guard (issue #263: Rust has no async Drop, so that guard cannot roll back itself and can only warn). ROLLBACK on a connection with no open transaction is a harmless, zero-row no-op — confirmed against the real engine — so this costs exactly the same one round-trip that the prior SELECT 1 probe did; it does not add a second round-trip.

Ping

Call AsyncConnection::ping on every checkout (equivalent round-trip, expressed via the connection’s own health primitive).

Unlike SelectOne, this does not discharge a transaction left open by a panicked or cancelled AsyncTransaction guard — ping only reads. Prefer SelectOne (the default) if your workload uses AsyncTransaction.

None

Skip connection validation entirely: no round-trip, and no passive check either — recycling is a genuine no-op, so a connection is handed out in whatever state the previous borrower left it. Use on hot paths where the round-trip cost outweighs detecting a dead connection early, and expect the failure to surface on first use instead.

Does not discharge a transaction left open by a panicked or cancelled AsyncTransaction guard — there is no round-trip at all to piggyback on. Avoid combining with AsyncTransaction unless you independently guarantee every transaction is committed or rolled back.

Custom(RecycleCheck)

Run a user-supplied async check on every checkout.

Like Ping, does not itself discharge a transaction left open by a panicked or cancelled AsyncTransaction guard; add an unconditional ROLLBACK to your check if your workload needs that.

Trait Implementations

impl Clone for RecycleStrategy

fn clone(&self) -> RecycleStrategy

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RecycleStrategy

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for RecycleStrategy

fn default() -> RecycleStrategy

Returns the “default value” for a type.