Enum Commit 

#[non_exhaustive]
pub enum Commit {
    Auto,
    Tracked,
    Transactional(String),
}

How processed deliveries are committed back to the consumer group.

Examples

A tracked subscription with one lane per record key, a cap on deliveries and a dead-letter topic:

use ruststream_rdkafka::prelude::*;
use serde::Deserialize;

#[derive(Deserialize)]
struct Payment {
    id: u64,
}

/// One lane per record key, so payments of one account stay ordered while others run
/// concurrently.
#[subscriber(
    KafkaTopic::new("payments")
        .group("payments-svc")
        .commit(Commit::Tracked)
        .start(StartOffset::Earliest)
        .lane_key(LaneKey::RecordKey),
    workers(8, by_key)
)]
async fn charge(payment: &Payment) -> HandlerOutcome {
    if payment.id == 0 {
        return HandlerOutcome::drop();
    }
    HandlerOutcome::ack()
}

fn app() -> RustStream {
    RustStream::new(AppInfo::new("payments", "0.1.0")).with_broker(
        KafkaBroker::new(["localhost:9092"]),
        |b| {
            // Five deliveries of one payment, the first included; the sixth goes to the
            // dead-letter topic instead, payload and headers as they arrived.
            b.include(charge)
                .max_attempts(nonzero!(5u32))
                .dead_letter("payments.dlq");
        },
    )
}

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.

Auto

librdkafka auto-commit, the librdkafka default: positions are stored as messages are handed to the application and committed every auto.commit.interval.ms. ack and nack(false) are advisory no-ops and nack(true) reports AckError::Unsupported; a crash can lose the tail of processed-but-uncommitted work or skip unprocessed deliveries that were already stored.

Tracked

Per-message acknowledgement: enable.auto.offset.store is switched off and an ack advances the stored position to just below the lowest still-unsettled delivery (or to the highest delivered offset once none are outstanding). At-least-once stays precise with concurrent handler lanes, and offset gaps the consumer never receives (transaction markers, compacted-away records) cannot block the position. Auto-commit still flushes the stored position in the background and once more when the consumer closes.

Transactional(String)

Exactly-once: the consumer never commits its own offsets - the EosPipeline whose transactional id matches this name commits them through the producer transaction (send_offsets_to_transaction), so source positions move atomically with the records the handlers publish. enable.auto.commit and enable.auto.offset.store are switched off; ack advances the shared watermark exactly like Tracked, and the pipeline picks the watermark up at its next window commit.

Trait Implementations

impl Clone for Commit

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 Commit

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

Formats the value using the given formatter.

impl Default for Commit

fn default() -> Self

Returns the “default value” for a type.

impl Eq for Commit

impl PartialEq for Commit

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Commit