Enum KafkaPosition 

#[non_exhaustive]
pub enum KafkaPosition {
    Earliest,
    Latest,
    Timestamp(i64),
    Offset {
        topic: Option<String>,
        partition: i32,
        offset: i64,
    },
}

Where a subscription should resume reading.

The stream-wide variants (Earliest, Latest, Timestamp) apply to every partition currently assigned to this consumer; Offset names one partition. Build them with the constructors (earliest, offset, …) - the variants are what the seeker matches on.

Examples

A read model rebuilt from the start of the retained log on every startup, whatever the group committed before:

use ruststream_rdkafka::prelude::*;

#[subscriber(
    KafkaTopic::new("orders").group("orders-projection"),
    start_at(KafkaPosition::earliest())
)]
async fn project(order: &Order) -> HandlerOutcome {
    tracing::info!(order.id, "projecting");
    HandlerOutcome::ack()
}

fn app() -> RustStream {
    RustStream::new(AppInfo::new("projection", "0.1.0"))
        .with_broker(KafkaBroker::new(["localhost:9092"]), |b| {
            b.include(project);
        })
}

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Earliest

The earliest offset still retained, on every assigned partition.

Latest

The end of the log, on every assigned partition, as the broker reports it while the seek runs: records published after that point arrive normally, everything before is skipped.

Timestamp(i64)

The first record at or after this timestamp (epoch milliseconds), resolved per assigned partition. A partition with no such record resumes at its end.

Offset

An absolute offset on one partition.

Fields

topic: Option<String>

The topic, when the position names one. Positioned captures the delivery’s own topic here; offset leaves it unset, which repositions that partition index on every assigned topic (one topic being the usual case).

partition: i32

The partition to reposition.

offset: i64

The offset to resume from: the record at this offset is delivered next.

Implementations

impl KafkaPosition

pub const fn earliest() -> Self

Every assigned partition, at the earliest retained offset.

pub const fn latest() -> Self

Every assigned partition, at the end of the log.

pub const fn offset(partition: i32, offset: i64) -> Self

One partition, at an absolute offset.

pub fn topic_offset( topic: impl Into<String>, partition: i32, offset: i64, ) -> Self

One partition of one topic, at an absolute offset. The form a delivery’s position returns, and what a multi-topic subscription needs to name a partition unambiguously.

pub const fn timestamp(when_millis: i64) -> Self

Every assigned partition, at the first record whose timestamp is at or after when_millis (epoch milliseconds).

Trait Implementations

impl Clone for KafkaPosition

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for KafkaPosition

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

Formats the value using the given formatter.

impl Eq for KafkaPosition

impl PartialEq for KafkaPosition

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for KafkaPosition