Struct Consumer 

pub struct Consumer { /* private fields */ }

High-level consumer that manages offset tracking and auto-commit.

Wraps one or more partitions across subscribed topics, polling them round-robin and tracking the latest consumed offset per partition.

Implementations

impl Consumer

pub async fn new(config: ConsumerConfig) -> Result<Self>

Create and connect a new consumer.

Connects to the first available bootstrap server, authenticates if configured, and discovers partition assignments for subscribed topics.

Auto-commit semantics

When auto_commit_interval is set, offsets are committed periodically at the next-fetch position. This provides at-most-once semantics: if the application crashes between poll() returning and the records being processed, those records will be skipped on restart.

For at-least-once semantics, disable auto-commit and call commit() explicitly after processing each batch.

pub fn set_rebalance_listener(&mut self, listener: Arc<dyn RebalanceListener>)

Register a rebalance listener for partition revocation/assignment events.

The listener is invoked during discover_assignments():

• on_partitions_revoked is called with the old assignment before reassignment
• on_partitions_assigned is called with the new assignment after reassignment

pub async fn poll(&mut self) -> Result<Vec<ConsumerRecord>>

Poll for new records across all assigned partitions.

Automatically reconnects with exponential backoff on connection errors and periodically re-discovers partition assignments.

pub async fn commit(&mut self) -> Result<()>

Commit current offsets to the server.

Automatically reconnects on connection errors.

pub fn seek(&mut self, topic: impl Into<String>, partition: u32, offset: u64)

Seek a specific partition to a given offset.

The next poll() will fetch from this offset for the specified partition.

pub fn seek_to_beginning(&mut self, topic: &str)

Seek all partitions of a topic to the beginning (offset 0).

pub fn position(&self, topic: &str, partition: u32) -> Option<u64>

Get the current offset position for a (topic, partition) pair.

pub fn assignments(&self) -> &HashMap<String, Vec<u32>>

Get current partition assignments.

pub fn group_id(&self) -> &str

Get the consumer group ID.

pub async fn close(self) -> Result<()>

Close the consumer, committing final offsets and leaving the group.