Trait ProjectionSource 

pub trait ProjectionSource: Sync {
    type Error: Error + Send + Sync + 'static;

    // Required methods
    fn source_id(&self) -> &DeliverySourceId;
    fn high_watermark(
        &self,
    ) -> impl Future<Output = Result<Option<DeliveryPosition>, Self::Error>> + Send;
    fn read_envelopes(
        &self,
        selection: &ProjectionSelection,
        after: Option<DeliveryPosition>,
        through: DeliveryUpperBound,
        limit: BatchSize,
    ) -> impl Future<Output = Result<Vec<PersistedEventEnvelope>, Self::Error>> + Send;
}

Backend-independent source of lossless, globally ordered persisted events.

A source owns a delivery sequence identified by a stable DeliverySourceId. Within that sequence, every persisted event has a unique, immutable, source-scoped DeliveryPosition, and global delivery order preserves each stream’s event order. Only committed events are visible. Once the source reports a committed frontier, no event may later appear at or below that frontier.

Required Associated Types

type Error: Error + Send + Sync + 'static

Error returned when the source cannot read its committed delivery sequence.

Required Methods

fn source_id(&self) -> &DeliverySourceId

Returns this source’s stable delivery identity.

The identity must remain the same across runs that use the same delivery sequence and position semantics. It must change when those semantics identify a different sequence.

fn high_watermark( &self, ) -> impl Future<Output = Result<Option<DeliveryPosition>, Self::Error>> + Send

Returns the committed high-water mark for the entire delivery sequence.

The result is independent of any ProjectionSelection. An empty committed source returns None; otherwise the result is the greatest committed delivery position. After a position is returned, the source must not later reveal a delivery at or below it that was not already committed and readable.

fn read_envelopes( &self, selection: &ProjectionSelection, after: Option<DeliveryPosition>, through: DeliveryUpperBound, limit: BatchSize, ) -> impl Future<Output = Result<Vec<PersistedEventEnvelope>, Self::Error>> + Send

Reads one selected page in ascending delivery order.

after is exclusive. DeliveryUpperBound::Inclusive is inclusive, while DeliveryUpperBound::Unbounded applies no upper position bound. Returned positions must be unique and strictly ascending. The source must apply the stream and event-type selection before applying limit, and it must return no more than limit envelopes. A zero limit returns an empty page. With a positive limit, an empty page means the selected committed sequence is exhausted within the requested position range. When through is a previously observed high-water mark, the source’s no-late-delivery guarantee makes that exhaustion stable through the bound.

Event types excluded by selection are intentionally omitted. A selected envelope with a malformed or unrepresentable field must instead produce an explicit error; it must not be silently skipped. Each returned PersistedEventEnvelope must preserve the source identity, delivery position, persisted event identity, stream identity and version, event type, raw payload, and raw metadata. Decoding that envelope into an application event is the application’s responsibility, not the source’s.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<T> ProjectionSource for &T

where T: ProjectionSource + ?Sized,

type Error = <T as ProjectionSource>::Error

fn source_id(&self) -> &DeliverySourceId

fn high_watermark( &self, ) -> impl Future<Output = Result<Option<DeliveryPosition>, <&T as ProjectionSource>::Error>> + Send

fn read_envelopes( &self, selection: &ProjectionSelection, after: Option<DeliveryPosition>, through: DeliveryUpperBound, limit: BatchSize, ) -> impl Future<Output = Result<Vec<PersistedEventEnvelope>, <&T as ProjectionSource>::Error>> + Send

Implementors

impl ProjectionSource for PostgresProjectionSource

type Error = PostgresProjectionSourceError