@deltic/offset-tracking

A general-purpose offset tracking abstraction for stream processing and event consumers.

Installation

npm install @deltic/offset-tracking

For the PostgreSQL implementation:

npm install @deltic/async-pg-pool pg

Usage

Interface

import type {OffsetRepository} from '@deltic/offset-tracking';

// Default types: Offset = number, Id = string
const offsets: OffsetRepository = /* implementation */;

const lastOffset = await offsets.retrieve('my-consumer');
// process events after lastOffset...
await offsets.store('my-consumer', newOffset);

In-Memory Implementation

import {OffsetRepositoryUsingMemory} from '@deltic/offset-tracking/memory';

const offsets = new OffsetRepositoryUsingMemory<number, string>();

PostgreSQL Implementation

import {OffsetRepositoryUsingPg} from '@deltic/offset-tracking/pg';

const offsets = new OffsetRepositoryUsingPg(asyncPool, {
    tableName: 'consumer_offsets',
    consumerName: 'projection-users',
    selectForUpdate: true, // optional: lock row during read
});

API Reference

OffsetRepository<Offset, Id> (interface)

| Method | Description | |--------|-------------| | retrieve(id) | Returns the stored offset or undefined | | store(id, offset) | Persists the offset for the given identifier |

License

ISC