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Redlock Implementation in TypeScript

This library provides a robust and distributed locking mechanism using the Redlock algorithm implemented in TypeScript. It allows you to acquire, release, and renew locks on shared resources across multiple Redis instances.

Features

• Acquire a distributed lock with configurable retry logic.
• Release a lock safely to ensure resource consistency.
• Renew locks to extend the time-to-live (TTL) for a lock.
• Support for custom retry strategies.
• Compatibility with multiple Redis clients for high availability.

Installation

1. Clone the repository or copy the Redlock.ts file into your project.
2. Install the required dependencies using npm or yarn:

npm install ioredis

Usage

Setup

Create Redis clients that implement the RedisClient interface and pass them to the Redlock class. For example, using ioredis:

import Redis from 'ioredis';
import { Redlock } from './Redlock';

const redisClients = [
  new Redis({ host: '127.0.0.1', port: 6379 }),
  new Redis({ host: '127.0.0.1', port: 6380 }),
  new Redis({ host: '127.0.0.1', port: 6381 }),
];

const redlock = new Redlock(redisClients);

Acquiring a Lock

You can acquire a lock on a resource with a specific TTL:

(async () => {
  const lock = await redlock.acquireLock('my-resource', 5000); // Lock for 5000ms
  if (lock) {
    console.log('Lock acquired:', lock);
  } else {
    console.log('Failed to acquire lock');
  }
})();

Acquiring a Lock with Custom Retry Strategy

To customize the retry strategy, pass a function to acquireLockWithCustomRetry:

(async () => {
  const retryStrategy = (attempt: number) => 100 * (attempt + 1); // Exponential backoff
  const lock = await redlock.acquireLockWithCustomRetry('my-resource', 5000, retryStrategy);
  if (lock) {
    console.log('Lock acquired with custom retry:', lock);
  } else {
    console.log('Failed to acquire lock with custom retry');
  }
})();

Releasing a Lock

To release a lock after use:

(async () => {
  const lock = await redlock.acquireLock('my-resource', 5000);
  if (lock) {
    await redlock.releaseLock(lock.resource, lock.value);
    console.log('Lock released');
  }
})();

Renewing a Lock

Extend the TTL of an existing lock:

(async () => {
  const lock = await redlock.acquireLock('my-resource', 5000);
  if (lock) {
    const renewed = await redlock.renewLock(lock.resource, lock.value, 5000);
    if (renewed) {
      console.log('Lock renewed');
    } else {
      console.log('Failed to renew lock');
    }
  }
})();

API Reference

acquireLock(resource: string, ttl: number): Promise<Lock | null>

Attempts to acquire a lock on the specified resource.
Parameters:

• resource: The resource to lock.
• ttl: The time-to-live for the lock in milliseconds.

Returns: A Lock object if successful, otherwise null.

acquireLockWithCustomRetry(resource: string, ttl: number, retryStrategy: (attempt: number) => number): Promise<Lock | null>

Attempts to acquire a lock using a custom retry strategy.
Parameters:

• resource: The resource to lock.
• ttl: The time-to-live for the lock in milliseconds.
• retryStrategy: A function that determines the delay before the next retry attempt.

Returns: A Lock object if successful, otherwise null.

releaseLock(resource: string, value: string): Promise<void>

Releases a lock on the specified resource.
Parameters:

• resource: The resource to unlock.
• value: The unique lock value.

Returns: A Promise that resolves when the lock is released.

renewLock(resource: string, value: string, ttl: number): Promise<boolean>

Renews the TTL for an existing lock.
Parameters:

• resource: The resource to renew the lock on.
• value: The unique lock value.
• ttl: The new TTL in milliseconds.

Returns: true if the lock was successfully renewed, otherwise false.

Notes

• Ensure all Redis clients are connected and synchronized for optimal performance.
• Use a unique value for each lock to prevent accidental unlocking by other processes.

License

This project is licensed under the MIT License. See the LICENSE file for details.