Struct SequenceHead 

pub struct SequenceHead { /* private fields */ }

Tracks the current persisted sequence head for one workflow history.

The head is the store’s expected_seq value: empty histories start at 0, and after appending N events the head advances by exactly N. Callers should advance this tracker only after the backing store has accepted the append.

Implementations

impl SequenceHead

pub const fn new() -> Self

Creates a tracker for a fresh workflow history at head 0.

pub const fn from_head(head: u64) -> Self

Creates a tracker from an explicitly derived persisted head.

pub const fn current(&self) -> u64

Returns the current store head to use as expected_seq.

pub const fn next_seq(&self) -> Option<u64>

Returns the sequence number for the first event in the next append batch.

pub fn mark_append_success( &mut self, event_count: usize, ) -> Result<(), DurabilityError>

Marks a successful append and advances the head by the number of appended events.

Advancing by zero is accepted as a no-op because stores may accept empty append batches, but the Recorder only records non-empty single-event batches.

Errors

Returns DurabilityError::HistoryShape if the event count cannot fit into u64 or if the resulting sequence head would overflow.

Trait Implementations

impl Clone for SequenceHead

fn clone(&self) -> SequenceHead

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SequenceHead

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

Formats the value using the given formatter.

impl Default for SequenceHead

fn default() -> SequenceHead

Returns the “default value” for a type.

impl Eq for SequenceHead

impl PartialEq for SequenceHead

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for SequenceHead