redis實現訊息佇列

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/**
 * @author sam
 * @date 2015/04/01
 * @desc a message queue
 */
var EventEmitter = require(‘events‘).EventEmitter;

var util = require(‘util‘);

/**
 * @cons
 * @param {client} a redis client
 * @param {priority:2} a number for set priority level, default 2 mean there have two priority level
 * */
var RedisMessageQueue = function(client, name, priority){

    if(name === null){
        throw new Error(‘message queue name is null‘);
    }

    this.name = name;

    priority = priority || 3; //系統預設具有三個優先順序的

    this.priority = priority < 1 ? 1 : priority;  //處理小於等於0的情況

    this.__client = client;

    this.__queueNames = [];

    this.__init();
};

RedisMessageQueue.EVENTS = {
    ERROR : ‘error‘
};

util.inherits(RedisMessageQueue,EventEmitter);


RedisMessageQueue.prototype.__init = function(){
    var self = this;
    //產生優先順序隊列名稱,*_0,*_1 數字小的優先順序高
    for(var i = 0 ; i < this.priority; i++){
        var messageQueueName = ‘message_queue_‘ + this.name + ‘_‘ + i;

        self.__queueNames[i] = messageQueueName;
        //非同步刪除
        //this.__client.del(messageQueueName);
    }

    this.__client.on(‘error‘,function(err){
        self.emit(RedisMessageQueue.EVENTS.ERROR,err);
    });

};


RedisMessageQueue.prototype.produce = function(message, level, callback){
    var self = this;

    if(message == null){
        callback && callback(null);
        return;
    }

    var str = null;

    var priority = self.__queueNames.length;

    //預設寫到最低優先順序隊列裡面去
    level = level || priority - 1;

    level = level < priority ? level : priority - 1;

    if(typeof message === ‘string‘){
        str = message;
    }else{
        try{
            str = JSON.stringify(message);
        }catch (ex){
            callback && callback(ex);
            return;
        }
    }

    self.__client.lpush(this.__queueNames[level],str,callback);

};

RedisMessageQueue.prototype.consume = function(cb){

    var self = this;    var queueNames = self.__queueNames;    var time = 0; //表示用戶端永遠等待    queueNames.push(time);    var client = self.__client;    client.brpop(queueNames,function(err,res){        if(err){            cb && cb(err);            return;        }        if(result === null){            cb && cb(null,null);            return;        }        var result = res[1];        try{            cb && cb(null, JSON.parse(result));            return;        }catch (ex){            if(typeof result === ‘string‘){                cb && cb(null, result);                return;            }            cb && cb(ex);        }    });};exports.RedisMessageQueue = RedisMessageQueue;

redis實現訊息佇列