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redis-semaphore
Advanced tools
Mutex and Semaphore implementations based on Redis ready for distributed systems
npm install --save redis-semaphore ioredis
# or
yarn add redis-semaphore ioredis
redisClient
- required, configured redis
clientkey
- required, key for locking resource (final key in redis: mutex:<key>
)options
- optional
lockTimeout
- optional ms, time after mutex will be auto released (expired)acquireTimeout
- optional ms, max timeout for .acquire()
callretryInterval
- optional ms, time between acquire attempts if resource lockedrefreshInterval
- optional ms, auto-refresh interval; to disable auto-refresh behaviour set 0
onLockLost
- optional function, called when lock loss is detected due refresh cycle; default onLockLost throws unhandled LostLockErrorconst Mutex = require('redis-semaphore').Mutex
const Redis = require('ioredis')
// TypeScript
// import { Mutex } from 'redis-semaphore'
// import Redis from 'ioredis'
const redisClient = new Redis()
async function doSomething() {
const mutex = new Mutex(redisClient, 'lockingResource')
await mutex.acquire()
try {
// critical code
} finally {
await mutex.release()
}
}
async function doSomething() {
const mutex = new Mutex(redisClient, 'lockingResource', {
// By default onLockLost throws unhandled LostLockError
onLockLost(err) {
console.error(err)
}
})
await mutex.acquire()
try {
while (mutex.isAcquired) {
// critical cycle iteration
}
} finally {
// It's safe to always call release, because if lock is no longer belongs to this mutex, .release() will have no effect
await mutex.release()
}
}
This implementation is slightly different from the algorithm described in the book, but the main idea has not changed.
zrank
check replaced with zcard
, so now it is fair as RedisLabs: Fair semaphore (see tests).
In edge cases (node time difference is greater than lockTimeout
) both algorithms are not fair due cleanup stage (removing expired members from sorted set), so FairSemaphore
API has been removed (it's safe to replace it with Semaphore
).
Most reliable way to use: lockTimeout
is greater than possible node clock differences, refreshInterval
is not 0 and is less enough than lockTimeout
(by default is lockTimeout * 0.8
)
redisClient
- required, configured redis
clientkey
- required, key for locking resource (final key in redis: semaphore:<key>
)maxCount
- required, maximum simultaneously resource usage countoptions
optional See Mutex
optionsconst Semaphore = require('redis-semaphore').Semaphore
const Redis = require('ioredis')
// TypeScript
// import { Semaphore } from 'redis-semaphore'
// import Redis from 'ioredis'
const redisClient = new Redis()
async function doSomething() {
const semaphore = new Semaphore(redisClient, 'lockingResource', 5)
await semaphore.acquire()
try {
// maximum 5 simultaneously executions
} finally {
await semaphore.release()
}
}
Same as Semaphore
with one difference - MultiSemaphore will try to acquire multiple permits instead of one.
MultiSemaphore
and Semaphore
shares same key namespace and can be used together (see test/src/RedisMultiSemaphore.test.ts).
redisClient
- required, configured redis
clientkey
- required, key for locking resource (final key in redis: semaphore:<key>
)maxCount
- required, maximum simultaneously resource usage countpermits
- required, number of acquiring permitsoptions
optional See Mutex
optionsconst MultiSemaphore = require('redis-semaphore').MultiSemaphore
const Redis = require('ioredis')
// TypeScript
// import { MultiSemaphore } from 'redis-semaphore'
// import Redis from 'ioredis'
const redisClient = new Redis()
async function doSomething() {
const semaphore = new MultiSemaphore(redisClient, 'lockingResource', 5, 2)
await semaphore.acquire()
try {
// make 2 parallel calls to remote service which allow only 5 simultaneously calls
} finally {
await semaphore.release()
}
}
Distributed Mutex
version
redisClients
- required, array of configured redis
client connected to independent nodeskey
- required, key for locking resource (final key in redis: mutex:<key>
)options
optional See Mutex
optionsconst RedlockMutex = require('redis-semaphore').RedlockMutex
const Redis = require('ioredis')
// TypeScript
// import { RedlockMutex } from 'redis-semaphore'
// import Redis from 'ioredis'
const redisClients = [
new Redis('127.0.0.1:6377'),
new Redis('127.0.0.1:6378'),
new Redis('127.0.0.1:6379')
] // or cluster.nodes('master')
async function doSomething() {
const mutex = new RedlockMutex(redisClients, 'lockingResource')
await mutex.acquire()
try {
// critical code
} finally {
await mutex.release()
}
}
Distributed Semaphore
version
redisClients
- required, array of configured redis
client connected to independent nodeskey
- required, key for locking resource (final key in redis: semaphore:<key>
)maxCount
- required, maximum simultaneously resource usage countoptions
optional See Mutex
optionsconst RedlockSemaphore = require('redis-semaphore').RedlockSemaphore
const Redis = require('ioredis')
// TypeScript
// import { RedlockSemaphore } from 'redis-semaphore'
// import Redis from 'ioredis'
const redisClients = [
new Redis('127.0.0.1:6377'),
new Redis('127.0.0.1:6378'),
new Redis('127.0.0.1:6379')
] // or cluster.nodes('master')
async function doSomething() {
const semaphore = new Semaphore(redisClients, 'lockingResource', 5)
await semaphore.acquire()
try {
// maximum 5 simultaneously executions
} finally {
await semaphore.release()
}
}
Distributed MultiSemaphore
version
redisClients
- required, array of configured redis
client connected to independent nodeskey
- required, key for locking resource (final key in redis: semaphore:<key>
)maxCount
- required, maximum simultaneously resource usage countpermits
- required, number of acquiring permitsoptions
optional See Mutex
optionsconst RedlockMultiSemaphore = require('redis-semaphore').RedlockMultiSemaphore
const Redis = require('ioredis')
// TypeScript
// import { RedlockMultiSemaphore } from 'redis-semaphore'
// import Redis from 'ioredis'
const redisClients = [
new Redis('127.0.0.1:6377'),
new Redis('127.0.0.1:6378'),
new Redis('127.0.0.1:6379')
] // or cluster.nodes('master')
async function doSomething() {
const semaphore = new RedlockMultiSemaphore(
redisClients,
'lockingResource',
5,
2
)
await semaphore.acquire()
try {
// make 2 parallel calls to remote service which allow only 5 simultaneously calls
} finally {
await semaphore.release()
}
}
MIT
redis-semaphore@5.0.0
ioredis@5
supportFAQs
Distributed mutex and semaphore based on Redis
The npm package redis-semaphore receives a total of 218,499 weekly downloads. As such, redis-semaphore popularity was classified as popular.
We found that redis-semaphore demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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