场景：使用node+mongo搭建web应用时，常常遇到并发问题导致创建一条数据的时候会同时创建多条。

通过redis set 方法 配合 ‘NX’ 选项即可实现锁机制。

主要的方法有三个：

lock(加锁)

unlock(解锁)

extend(更改锁过期时间)

Redlock.prototype.lock = function(resource,ttl,callback){  var self = this;  var _val = _random();  return new Promise(function(resolve, reject) {    var lock = new Lock(self, resource, _val);    self.client.SET(resource,_val,'EX',ttl,'NX',function(err,data){      if(!err && data === 'OK'){        return resolve(lock);      }else{        var err = err || 'resource: '+resource+' is locked.';        self.emit('lockError', err);        return reject(err);      }    })  }).asCallback(callback);}

Redlock.prototype.unlock = function(lock,callback){  var self = this;  return new Promise(function(resolve, reject) {    if(typeof lock !== 'object') return reject('unlockError:lock is not object.');    self.client.GET(lock.resource,function(err,data){      if(!err && data === lock.value){        self.client.DEL(lock.resource,function(err){          if(err){            self.emit('unlockError',err);            return reject('unlockError:'+err);          }else{            return resolve(lock);          }             })      }else{        self.emit('unlockError',err || 'resource:' + lock.resource + ' unable to unlock.')        return reject('unlockError:' + err || ('resource:' + lock.resource + ' unable to unlock.'));      }    })  }).asCallback(callback);}

Redlock.prototype.extend = function(lock,ttl,callback){  var self = this;  return new Promise(function(resolve, reject){    if(typeof lock !== 'object') return reject('unlockError:lock is not object.');    self.client.GET(lock.resource,function(err,data){      if(!err && data === lock.value){        self.client.expire(lock.resource,ttl,function(err,data){          if(!err && data === 1){            return resolve(lock);          }else{            self.emit('extendError', err);            return reject('extendError:'+err);          }                  });      }else{        self.emit('extendError', err);        return reject('extendError:'+err);      }    })  }).asCallback(callback);}

用法

var client = require('redis').createClient('port','host');var redlock = new RedLock(client);var lock;`callback`://lockredlock.lock('test-resource-lock',3,function(err,lockInstance){  lock = lockInstance;  done(err);});//unlockredlock.unlock(lock,function(err,data){  done(err);});`promise`:redlock.lock('test-resource-lock-promise',3).done(  function(lock){    //todo    redlock.unlock(lock);  },  function(){  })

PS:支持callback and promise.

实现比较简单，100行内，有兴趣的可以在 查看源码