nickleefly nickleefly - 4 months ago 21
Node.js Question

How to reuse mongodb connection in node.js

I'm using node-mongodb-native driver with mongodb to write a website.

I have a question about how to open mongodb connection once, then use it in collection name users in

user.js
and collection name posts in
comment.js


I want to open db connection in
db.js
then to insert / save data for users and posts collection

Currently code,my
db.js


var Db = require('mongodb').Db,
Connection = require('mongodb').Connection,
Server = require('mongodb').Server;
module.exports = new Db(
'blog',
new Server('localhost', Connection.DEFAULT_PORT, {auto_reconnect: true})
);


I used
db.js
in
user.js
as follow

var mongodb = require('./db');

function User(user){
this.name = user.name;
this.password = user.password;
this.email = user.email;
};

module.exports = User;

User.prototype.save = function(callback) {//save user information
//document to save in db
var user = {
name: this.name,
password: this.password,
email: this.email
};
mongodb.close();
//open mongodb database
mongodb.open(function(err, db){
if(err){
return callback(err);
}
//read users collection
db.collection('users', function(err, collection){
if(err){
mongodb.close();
return callback(err);
}
//insert data into users collections
collection.insert(user,{safe: true}, function(err, user){
mongodb.close();
callback(err, user);//success return inserted user information
});
});
});
};


and
comment.js


var mongodb = require('./db');

function Comment(name, day, title, comment) {
this.name = name;
this.day = day;
this.title = title;
this.comment = comment;
}

module.exports = Comment;

Comment.prototype.save = function(callback) {
var name = this.name,
day = this.day,
title = this.title,
comment = this.comment;
mongodb.open(function (err, db) {
if (err) {
return callback(err);
}
db.collection('posts', function (err, collection) {
if (err) {
mongodb.close();
return callback(err);
}
//depend on name time and title add comment
collection.findAndModify({"name":name,"time.day":day,"title":title}
, [ ['time',-1] ]
, {$push:{"comments":comment}}
, {new: true}
, function (err,comment) {
mongodb.close();
callback(null);
});
});
});
};

Answer

You can connect once, and then reuse it as many times as you want:

var mongodb = require('mongodb');
var events = require('events');
var event = new events.EventEmitter();
var access = new mongodb.Server(host, port, { });
var client = null;

new mongodb.Db('YOUR DATABASE', access, { safe: true, auto_reconnect: true }).open(function (err, c) {
  if (!err) {
    client = c;
    console.log('database connected');
    event.emit('connect');
  } else {
    console.log('database connection error', err);
    event.emit('error');
  }
});

exports.get = function(fn) {
  if(client) {
    fn(client);
  } else {
    event.on('connect', function() {
      fn(client);
    });
  }
};

And then reuse it:

var db = require('./db');
var items;
db.get(function(client) {
  items = new mongodb.Collection(client, 'collection');
});

// then anywhere in your code
db.get(function() {
  // items.find({ ...
});
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