pub fn classify(
declaration: QueueDeclaration,
census: &PoolCensus,
) -> Option<QueueServiceReason>Expand description
Classify one selection miss into the taxonomy.
Returns None when the address is in fact served — the caller raced a
worker arriving and must simply retry selection rather than report a state
that is no longer true.
Ordering is deliberate: a structurally undeclared queue is reported as
QueueServiceReason::NoQueueDeclaration even when unrelated workers sit
in the pool, because that is the deeper fact and the only one that refuses
unconditionally. QueueDeclaration::Unknown never manufactures a
structural refusal — the same fail-open discipline worker registration
applies when no catalog is reachable.
QueueServiceReason::Saturated is never produced here: it is not a
selection miss. It is emitted by the delivery path
(super::delivery::deliver_within_schedule_to_start) when a compatible
worker is live and refuses intake past the schedule-to-start clock.