node-redis-warlock

warlock

Battle-hardened distributed locking using redis.

Requirements

• node-redis compatible with v0.10
• Redis v2.6 or above

Install

npm install node-redis-warlock

Usage

var Warlock = require('node-redis-warlock');
var redis = require('redis');

// Establish a redis client and pass it to warlock
var redis = redis.createClient();
var warlock = Warlock(redis);

// Set a lock
var key = 'test-lock';
var ttl = 10000;

warlock.lock(key, ttl, function(err, unlock){
  if (err) {
    // Something went wrong and we weren't able to set a lock
    return;
  }

  if (typeof unlock === 'function') {
    // If the lock is set successfully by this process, an unlock function is passed to our callback.
    // Do the work that required lock protection, and then unlock() when finished...
    //
    // do stuff...
    //
    unlock();
  } else {
    // Otherwise, the lock was not established by us so we must decide what to do
    // Perhaps wait a bit & retry...
  }
});

ProTips

• Warlock uses Lua scripting to achieve transactional locking on Redis v2.6.0 upwards. If you're running Redis v2.6.12 or above you could use the additional PX and NX arguments for the SET operation as an alternative.
• Read my Distributed locks using Redis article and Redis' author's A proposal for more reliable locks using Redis to learn more about the theory of distributed locks using Redis.