mongodb（mongoose-redis-cache）

在node与mongodb的项目中也仍然会存在类似问题，本文参考了mongoose-redis-cache这个插件。

https://github测试数据/conancat/mongoose-redis-cache

该插件还不太完善，但基本的思路是很简单的，初始化一个redis客户端，然后重写mongoose的exec方法，将exec的参数设置为redis的key，将数据库返回的结果设置为对应的value。

每次操作时优先读取redis。

代码如下：

 //   Generated by CoffeeScript 1.5.0 
 var   mongooseRedisCache, redis, _;

redis  = require("redis" );

_  = require("underscore" );

mongooseRedisCache  =  function  (mongoose, options, callback) {
    var   client, host, pass, port, redisOptions;
    if  (options ==  null  ) {
    options  =  {};
  }
  host  = options.host || "" ;
  port  = options.port || "" ;
  pass  = options.pass || "" ;
  redisOptions  = options.options ||  {};
  mongoose.redisClient  = client =  redis.createClient(port, host, redisOptions);
    if  (pass.length > 0 ) {
    client.auth(pass,   function  (err) {
        if   (callback) {
          return   callback(err);
      }
    });
  }

 //这里做了改动，原来是execFind，在我当前的Mongoose版本下无法使用 
  mongoose.Query.prototype._exec  =  mongoose.Query.prototype.exec;
  mongoose.Query.prototype.exec  =  function  (callback) {

      var   cb, expires, fields, key, model, query, schemaOptions, self;
    self  =  this  ;
    model  =  this  .model;
    query  =  this  ._conditions;
    options  =  this  ._optionsForExec(model);
    fields  = _.clone( this  ._fields);
    schemaOptions  =  model.schema.options;
    expires  = schemaOptions.expires || 60 ;

      if  (!schemaOptions.redisCache &&  options.lean) {
        return   mongoose.Query.prototype._exec.apply(self, arguments);
    }
    key  = JSON.stringify(query) + JSON.stringify(options) +  JSON.stringify(fields);
    
    cb  =  function  (err, result) {
        var   docs;
        if   (err) {
          return   callback(err);
      }
        if  (! result) {
          return  mongoose.Query.prototype._exec.call(self,  function  (err, docs) {
            var   str;
            if   (err) {
              return   callback(err);
          }
          str  =  JSON.stringify(docs);
          client.set(key, str);
          client.expire(key, expires);
            return  callback( null  , docs);
        });
      }   else   {
        docs  =  JSON.parse(result);
          return  callback( null  , docs);
      }
    };
    client.get(key, cb);
      return   this  ;
  };
};

module.exports  = mongooseRedisCache;

写测试用例如下：

 var  mongoose = require(‘mongoose‘ );

  var  async = require(‘async‘ );
  var  mongooseRedisCache = require("mongoose-redis-cache" );
mongooseRedisCache(mongoose);
  var  Schema =  mongoose.Schema;

mongoose.connect( ‘mongodb://localhost/cachetest‘ );

  var  user =  new   Schema({
    username:{
        type:String,
        index:  true  
    },
    password:String
});

user.set( ‘redisCache‘,  true  );

  var  userModel = mongoose.model(‘user‘ , user);

  var  entity =  new   userModel({
    username: ‘fredric‘ ,
    password: ‘sinny‘ 
});

  var  users =  [];
  for ( var  i = 0; i < 1000; i++ ){
    users.push({
        username: ‘fredric‘ +  i,
        password: ‘sinny‘ +  i
    });
}

  function   testCache(){

      function   datainit(item,cb){
          var  entity =  new   userModel(item);
        entity.save(  function  (err){
            cb(err);
        });
    }
    
    async.mapSeries(users, datainit,   function  (err, results){
        
        console.log( ‘datainit finished‘ );
        
          var  timestamp =  new   Date().valueOf();
        
          var  round =  [];
          for ( var  i = 0; i < 2000; i++ ){
            round.push(i);
        }
        
          //  利用缓存 
         function   test(item,cb){
            query  = userModel.find({‘username‘:‘fredric101‘ });
            query.lean();
            query.exec(  function  (err, result){
                cb(err);
            });
        }
        
        
          //  不利用缓存 
         function   test_nocache(item,cb){
            query  = userModel.find({}).setOptions({nocache:  true  });
            query.where( "username", "fredric101" );
            query.exec(  function  (err, result){
                cb(err);
            });
        }
        
        async.mapSeries(round, test_nocache,   function  (err, results){
            console.log(  new  Date().valueOf() -  timestamp);
        });
    });    
}
testCache(); 

测试结果还是比较明显的，在我本地笔记本上（安装redis + mongodb），上述测试用例执行：

1、无缓存、无索引：21501ms

2、无缓存、有索引：1966ms

3、有缓存、有索引：281ms

mongodb（mongoose-redis-cache）

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