vercel / redis-semaphore

Distributed mutex and semaphore based on Redis

redis-semaphore

Mutex and Semaphore implementations based on Redis ready for distributed systems

Features

• Fail-safe (all actions performed by LUA scripts (atomic))

Usage

Mutex

new Mutex(redisClient, key [, { lockTimeout = 10000, acquireTimeout = 10000, retryInterval = 10, refreshInterval = acquireTimeout * 0.8 }])

• redisClient - required, configured redis client
• key - required, key for locking resource (final key in redis: mutex:<key>)
• timeouts optional
  • lockTimeout - ms, time after mutex will be auto released (expired)
  • acquireTimeout - ms, max timeout for .acquire() call
  • retryInterval - ms, time between acquire attempts if resource locked
  • refreshInterval - ms, auto-refresh interval

Example

const Mutex = require('redis-semaphore').Mutex
const redis = require('redis')

const redisClient = redis.createClient()

async function doSomething() {
  const mutex = new Mutex(redisClient, 'lockingResource')
  await mutex.acquire()
  // critical code
  await mutex.release()
}

Semaphore

new Semaphore(redisClient, key, maxCount [, { lockTimeout = 10000, acquireTimeout = 10000, retryInterval = 10, refreshInterval = acquireTimeout * 0.8 }])

• redisClient - required, configured redis client
• key - required, key for locking resource (final key in redis: semaphore:<key>)
• maxCount - required, maximum simultaneously resource usage count
• timeouts optional
  • lockTimeout - ms, time after semaphore will be auto released (expired)
  • acquireTimeout - ms, max timeout for .acquire() call
  • retryInterval - ms, time between acquire attempts if resource locked
  • refreshInterval - ms, auto-refresh interval

Example

const Semaphore = require('redis-semaphore').Semaphore
const redis = require('redis')

const redisClient = redis.createClient()

async function doSomething() {
  const semaphore = new Semaphore(redisClient, 'lockingResource', 5)
  await semaphore.acquire()
  // maximum 5 simultaneously executions
  await semaphore.release()
}

Installation

npm install --save redis-semaphore
# or
yarn add redis-semaphore

License

MIT