Redlock

This is a node.js implementation of the redlock algorithm for distributed redis locks. It provides strong guarantees in both single-redis and multi-master environments, and is fault tolerant in the latter. Full support for redis cluster using ioredis is planned and will be available shortly.

Installation

npm install --save redlock

Configuration

Redlock can use node redis or any compatible redis library to keep its client connections.

A redlock object is instantiated with a required options parameter and at least one redis client parameter. Properties of the Redlock object should NOT be changed after it is first used, as doing so could have unintended consequences for currently-processing locks.

var client1 = require('redis').createClient(6379, 'redis1.example.com');
var client2 = require('redis').createClient(6379, 'redis2.example.com');
var Redlock = require('redlock');

var redlock = new Redlock(
	{
		// the expected clock drift; for more details
		// see http://redis.io/topics/distlock
		driftFactor: 0.01,
		
		// the max number of times Redlock will attempt
		// to lock a resource before erroring
		retryCount:  3,
		
		// the time in ms between attempts
		retryDelay:  200
	},
	
	// you should have one client for each redis node
	// in your cluster
	client1,
	client2
);

Usage

###Locking & Unocking

// the string identifier for the resource you want to lock
var resource = 'locks:account:322456';

// the maximum amount of time you want the resource locked,
// keeping in mind that you can extend the lock up until
// the point when it expires
var ttl = 1000;

redlock.lock(resource, ttl, function(err, lock) {

	// we failed to lock the resource
	if(err) {
		// ...
	}
	
	// we have the lock
	else {


		// ...do something here...


		// unlock your resource when you are done
		lock.unlock();
	}
});

###Locking and Extending

redlock.lock('locks:account:322456', 1000, function(err, lock) {

	// we failed to lock the resource
	if(err) {
		// ...
	}
	
	// we have the lock
	else {


		// ...do something here...


		// if you need more time, you can continue to extend
		// the lock until it expires
		lock.extend(1000, function(err, lock){

			// we failed to extend the lock on the resource
			if(err) {
				// ...
			}


			// ...do something here...


			// unlock your resource when you are done
			lock.unlock();
		}
	}
});

API Docs

###Redlock.lock(resource, ttl, callback)

• resource (string) resource to be locked
• ttl (number) time in ms until the lock expires
• callback (function) callback returning:
  • err (Error)
  • lock (Lock)

###Redlock.unlock(lock, callback)

• lock (Lock) lock to be released
• callback (function) callback with no returning arguments

###Redlock.extend(lock, ttl, callback)

• lock (Lock) lock to be extended
• ttl (number) time in ms to extend the lock's expiration
• callback (function) callback returning:
  • err (Error)
  • lock (Lock)

###Lock.unlock(callback)

• callback (function) callback with no returning arguments

###Lock.extend(ttl, callback)

• ttl (number) time in ms to extend the lock's expiration
• callback (function) callback returning:
  • err (Error)
  • lock (Lock)