Struct KafkaMessage 

pub struct KafkaMessage { /* private fields */ }

One Kafka delivery: an owned snapshot of the record plus its settlement handle.

Settlement mapping depends on the Commit mode of the subscription:

Under Commit::Auto (the default) librdkafka owns the committed position - it is stored the moment a message is handed to the application - so ack and both nack forms are advisory no-ops; in particular nack(true) does NOT cause a redelivery.

Under Commit::Tracked:

• ack settles the offset and advances the stored position across everything settled below it.
• nack(false) drops the message: the offset settles so the position can move past it (Kafka has no per-message dead-letter path; a dead-letter topic is a planned descriptor option).
• nack(true) leaves the offset unsettled: the committed position stays below it, so Kafka redelivers from there when the partition is next re-fetched (a rebalance or a restart). Until then the unsettled offset also blocks the position, keeping every later ack uncommitted - precise, but worth knowing when a handler nacks in a loop.

Wire headers map name for name; a null-valued Kafka header arrives with an empty value (presence preserved).

Implementations

impl KafkaMessage

pub fn topic(&self) -> &str

The topic this record was consumed from.

pub fn partition(&self) -> i32

The partition this record was consumed from.

pub fn offset(&self) -> i64

The record’s offset within its partition.

pub fn timestamp_millis(&self) -> Option<i64>

The record’s timestamp in milliseconds since the epoch, when the broker provided one.

pub fn key(&self) -> Option<&[u8]>

The record key, surfaced from Kafka’s native key (see PARTITION_KEY_HEADER).

Trait Implementations

impl BuildContext<KafkaMessage> for KafkaContext

fn build(msg: &KafkaMessage) -> Self

Builds the context value by reading fields out of msg.

impl Debug for KafkaMessage

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

Formats the value using the given formatter.

impl IncomingMessage for KafkaMessage

async fn ack(self) -> Result<(), AckError>

Marks the offset processed (see the type-level settlement mapping).

Errors

Returns AckError::Broker when the offset store rejects the new position, for example because enable.auto.offset.store was overridden back to true on a Commit::Tracked subscription.

Cancel safety

Cancel safe: the watermark update is synchronous, so the future either completed or did nothing.

async fn nack(self, requeue: bool) -> Result<(), AckError>

Settles negatively. With a Retry policy configured on the subscription, requeue = true runs it (republish to the retry topic, seek back, or drop) and requeue = false runs the drop path (dead-letter when configured, then settle). Without a policy, requeue = false settles the offset and requeue = true leaves it unsettled for Kafka’s native re-consumption - which under Commit::Auto makes both forms advisory no-ops (see the type-level settlement mapping).

Errors

Returns AckError::Broker when a retry/dead-letter republish or seek fails, and under the same conditions as ack.

Cancel safety

Without a policy: cancel safe (the watermark update is synchronous). With a policy: not cancel safe - dropping the future may leave the retry or dead-letter copy published with the original unsettled (a duplicate, never a loss).

fn partition_key(&self) -> Option<&[u8]>

The keyed-lane key, so keyed worker lanes see it without a Partitioned bound: the source partition (the default), or the record key under LaneKey::RecordKey.

fn payload(&self) -> &[u8]

Returns the raw payload of the message.

fn headers(&self) -> &Headers

Returns the headers attached to the message.

fn supports_nack_after(&self) -> bool

Reports whether this transport can honor nack_after natively.

fn nack_after( self, delay: Duration, ) -> impl Future<Output = Result<(), AckError>> + Send

where Self: Sized,

Negatively acknowledges the message, asking the broker to redeliver it no sooner than delay from now.

impl Partitioned for KafkaMessage

fn partition_key(&self) -> Option<&[u8]>

The keyed-lane key (see IncomingMessage::partition_key on this type): the source partition (the default), or the record key under LaneKey::RecordKey.