Enum VacateOutcome 

pub enum VacateOutcome {
    Released {
        generation: u64,
        released: Assignee,
    },
    Stale {
        current: Option<Assignee>,
    },
}

What RunStore::vacate_assignee did — it releases a seat only while that seat still holds the generation the caller observed, so “released” and “someone else got there first” are two answers, not one.

Why a release has to name a generation

A release is issued by a caller that read the holder earlier and then decided it should go: A7 reads a holder, asks its adapter for T-ALIVE, and releases on Disconnected; O8’s cascade reads a holder, matches it against a deleted operator’s names, and releases. Both decisions are about the Assignee that was read, and both have .await points between the read and the write, during which an acquire (which never excludes — A8) can seat somebody else.

Addressed at (run, slot) alone, such a release would delete whatever holder happened to be there — a holder whose liveness was never asked for and whose deletion no premise in the model supports. That is a lost update, not A8: the acquirer was answered 200 with its generation (Q4) and has no channel to learn it was undone. Carrying the observed generation turns the write back into the decision that was actually made.

gen alone identifies the holder because G is Run-wide and advances on every assignment event, so a generation is never reused — a seat holding expected_gen is holding the very instance the caller read, including when a re-acquire put the same operator back (A8).

Variants

Released

The seat still held the observed generation, so it was released and the slot is now Vacant.

Fields

generation: u64

The Run-wide counter G after this event (A4: a Vacant advances it exactly like an Assign does).

released: Assignee

The holder that was released — the instance the caller read.

Stale

The seat did not hold the observed generation, so nothing was written: no holder removed, G not advanced, updated_at untouched.

The caller’s reading is stale — either an acquire moved the seat on (A8 already decided that contest, and the newer holder stands) or the seat was released by someone else in between. Either way the release is not re-issued against the new state: the decision behind it was made about a holder that is no longer there.

Fields

current: Option<Assignee>

Who holds the seat now, for the message the caller reports. None = the slot is already Vacant.

Trait Implementations

impl Clone for VacateOutcome

fn clone(&self) -> VacateOutcome

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for VacateOutcome

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

Formats the value using the given formatter.

impl Eq for VacateOutcome

impl PartialEq for VacateOutcome

fn eq(&self, other: &VacateOutcome) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for VacateOutcome