Struct StateWatch 

pub struct StateWatch<K, V, T, D> {
    metrics: Arc<Metrics>,
    state: Arc<LockingTypedState<K, V, T, D>>,
    seqno_high_water: SeqNo,
    seqno_rx: Receiver<SeqNo>,
    upper_rx: Receiver<Antichain<T>>,
}

A reactive subscription to changes in LockingTypedState.

This exposes two independent signals over the same state:

• Self::wait_for_seqno_ge wakes on any strict seqno advance.
• Self::wait_for_upper_past wakes only when the shard upper advances.

Invariants:

• The state.seqno only advances (never regresses). This is guaranteed by LockingTypedState.
• seqno_high_water is always <= state.seqno.
• If seqno_high_water is < state.seqno, then we’ll get a notification on seqno_rx. This is maintained by notifying new seqnos under the same lock which adds them.
• seqno_high_water always holds the highest value received on seqno_rx. This is maintained by the wait method taking an exclusive reference to self.
• upper_rx holds the shard upper, advanced under the same lock that advances the upper. It coalesces, so a waiter always observes the latest upper.

Fields

metrics: Arc<Metrics>

state: Arc<LockingTypedState<K, V, T, D>>

seqno_high_water: SeqNo

seqno_rx: Receiver<SeqNo>

upper_rx: Receiver<Antichain<T>>

Implementations

impl<K, V, T, D> StateWatch<K, V, T, D>

pub(crate) fn new( state: Arc<LockingTypedState<K, V, T, D>>, metrics: Arc<Metrics>, ) -> Self

pub async fn wait_for_seqno_ge(&mut self, requested: SeqNo) -> &mut Self

Blocks until the State has a SeqNo >= the requested one.

This method is cancel-safe.

pub async fn wait_for_upper_past( &mut self, frontier: &Antichain<T>, ) -> &mut Self

where T: Timestamp,

Blocks until the shard upper has advanced past frontier.

Unlike Self::wait_for_seqno_ge, this only wakes on upper advances, not on seqno bumps caused by GC, rollups, since-downgrades, or no-op CaAs.

This method is cancel-safe.

Trait Implementations

impl<K: Debug, V: Debug, T: Debug, D: Debug> Debug for StateWatch<K, V, T, D>

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

Formats the value using the given formatter.