MongoCache.js

var mongoose = require('mongoose');
var moment = require('moment');
var config = require('../../config/environment');


// setup Redis client that supports both local machine with redis-mock and production server
var redis = null;
var client;
if (! redis) {
  if (process.env.NODE_ENV != 'development') {
        redis = require('redis');
        client = redis.createClient(6379, config.redisEndpoint, {no_ready_check: false});
        client.on('error', function (e) {
            console.log("Redis Client Error" +  e.toString());
            client.quit();
        });
    }
    else {
        redis = require("redis-mock");
        client = redis.createClient();
    }
}


// counting cache hits and cache misses - also use Redis for this
function internalInc(k) {
  setTimeout(function(){
    var key = "0" + config.redisPrefix + k + moment().utc().format('MM-DD-YYYY');
    var multi = client.multi();
    multi.expire(key, 24 * 60 * 60);
    multi.incr(key);
    multi.exec(function (err, data) {
      if (err) { console.log("Redis error", err) };
    })
  },0);
}


function incMongoCacheHits(){
    var k = "mongoCacheHits";
    internalInc(k);
};

function incMongoCacheMiss(){
    var k = "mongoCacheMiss";
    internalInc(k);
};


var redisKey = function(table, field, value){
    return "0" + config.redisPrefix + "_MC_" + table.collection.collectionName + "_" + field + "_" + value;
}


// call this when a mongo object is saved in order to remove it from the cache. It will be lazy-loaded when required
var touchObject = function (table, fields, cb) {
    var multi = client.multi();
    for (var k in fields) {
        var key = redisKey(table, k, fields[k]);
        multi.del(key);
    }

    multi.exec(function(err,val){
        if(err) return cb(err);
        return cb(null);
    });
}


// get a single MongoDB item by field and value
//   table - mongoose collection definition
// will search the item in Redis and if not found will be loaded from MongoDB, saved to redis, and returned to the requester
// note: the returned object is a clone and cannot be eddited or saved to MongoDB.
// example:
//  MongoCache.getObjectByField(Customer, MongoCache.ID, customerId, function (err, item) { ... });
var getObjectByField = function(table, field, value, cb){
    var key = redisKey(table, field, value);
    client.get(key,function(err,val){
        if(err) return cb(err);
        if (val == null) {
            console.log("MongoCacheMiss " + key);

            incMongoCacheMiss();
            var query;
            if (!field || field == idField) {
                query = table.findById(value);
            } else {
                var filter = {}
                filter[field] = value;
                query = table.findOne(filter)
            }
            query.lean().exec(function(err, item) {
                if (err) return cb(err);
               client.setex(key, 60*60, JSON.stringify(item), function (err) {
                   if (err) return cb(err);
                   return cb(null, item);
               });
            });
        } else {
            try{
                var ret = JSON.parse(val);
                incMongoCacheHits();
            }
            catch(e){
              return cb("redis_mongoCache_get---" + key + " " + e + "  " +val);
            }
            return cb(null,ret);
        }

    });
}
var idField = "_id";

var MongoCache = {
    touchObject: touchObject,
    getObjectByField: getObjectByField,
    ID : idField
};

module.exports = MongoCache;