Module offset 

Client-side offset persistence for LANCE consumers

Provides traits and implementations for storing consumer offsets locally, enabling stateless broker architecture per the Client-Managed Offset Strategy.

Design Philosophy

LANCE treats the broker as a stateless data pipe. Offset tracking is the client’s responsibility, enabling:

• Exactly-once semantics (store offset with business data atomically)
• Stateless horizontal scaling
• Reduced broker metadata overhead

Example

use lnc_client::offset::{OffsetStore, LockFileOffsetStore};
use std::path::Path;

let store = LockFileOffsetStore::open(
    Path::new("/var/lib/lance/offsets"),
    "my-consumer",
)?;

// Load stored offset for a topic
let offset = store.load(topic_id, consumer_id).unwrap_or(0);

// After processing, save the new offset
store.save(topic_id, consumer_id, new_offset)?;

Structs

CollectingCommitHook

A hook that collects commit events for testing

CommitInfo

Information about a committed offset

HookedOffsetStore

Offset store wrapper that invokes post-commit hooks

LockFileOffsetStore

File-based offset store with lock file protection

LoggingCommitHook

A simple logging hook for debugging

MemoryOffsetStore

In-memory offset store for testing and ephemeral consumers

Traits

OffsetStore

Trait for client-side offset persistence

PostCommitHook

Trait for post-commit hooks