I created my Schema's in my models/mymodel.js file. I also have my models in there as well as my methods.
How do I export them into my routes?
// route.js
var mongoose = require("mongoose");
var Posts = mongoose.model("posts")
...
Ensure that you set up a bootstrap mechanism that runs all your model files. Once that is done you should have called mongoose.model("name", Model) for a set of models.
This has cached those models in mongoose internally. So you can just call mongoose.model("name") anywhere you want.
The only thing that's important is order of execution. The model & schemas need to be registered before you run your routes.
This is as a simple as :
// create app
var app = express.createServer(...);
// do stuff with app
var files = fs.readdirSync("models");
files.forEach(function(file) {
require("models/" + file);
});
var routes = fs.readdirSync("routes");
routes.forEach(function(route) {
require("routes/" + route)(app);
});
app.listen(80);
Note that normally readdirSync is evil but it's ok to execute blocking calls at startup time (like require) before your listen to your server
Mongoose creates a singleton when you require() it, and subsequent calls return the same instance.
So as long as you require mongoose when your app inits, then define your models, they will be available in any other file where you require mongoose as described by Raynos.
Unless you want to manage connections to the db server manually, it's also a good idea to call mongoose.connect('...') in your app init; the connection will persist across requests.
Related
I have a Node/Express app that uses Mongoose to talk to a MongoDB database. The Express server is configured in a file called server.js and the schema is in a separate models.js file. Following every project and tutorial I've seen so far, I have the mongoose.connect() configured in both places:
// server.js
const express = require('express');
const cookieParser = require('cookie-parser');
const bodyParser = require('body-parser');
const mongoose = require('mongoose');
const app = express();
mongoose.connect('mongodb://127.0.0.1/mydb');
// models.js
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const User = new Schema({
username: String,
password: { type: String, select: false },
name: String,
});
module.exports = mongoose.model('User', User);
My question is, since I'm already importing mongoose in models.js, can I not skip doing so in server.js entirely and just set the connection in the model script itself? What's the point of importing it and configuring a connection along with the rest of the server config when I'm only going to use it when working with the schema? And If the answer is yes, why doesn't anyone do that? Is there a performance benefit at play here?
You could do mongoose.connect() in your model script but this would not be advisable.
You would have to ensure that this model was loaded before any other scripts that required the mongoose connection.
If you go on to create another model in your application, then this would rely on your User model (model.js) having been loaded first.
You would have to perform the connection in each model just to be sure, but this would be a poor design and unnecessary code duplication.
Therefore, connecting in server.js is the best approach to ensure the connection is established as early as possible.
It is not necessary that you require the mongoose in the server.js file. In fact in my project I create a separate file for each connection like connection_one.js, connection_two.js and export the mongoose object. This way when any number of models does a require("./connection_one.js") it will return the same connection ready mongoose for all models exporting it. This is possible due to modules are cached on first time load inside a project. It is what is also happening when you are loading the mongoose module in server.js, it is the same mongoose object in server.js and model.js.
To address you question, first of all you need to understand object-oriented programming. Right now, you have two different files. One if server.js. and another is models.js. And each file has it's own scope.
Even if you imported mongoose in server.js since the two scopes has different scope set, models.js cannot utilize the mongoose service imported in server.js. For example, let say you defined a variable "foo",
You cannot use that variable in model.js because their scopes are isolated.
// server.js
const foo = 'bar';
If you want to use only one mongoose imported in a single script and shared by others, you can use global object from Node.js env. Check out the url to know more about this.
node.js global variables?
However, I don't really recommned putting mongoose service in gloabl object. Global scope can be easy at the beginning, but it could be significant scalability problem as your application grows bigger in later time.
Thanks.
I have a web app under development. I found CW Buechler's tutorial on how to make a simple one very useful but have a couple of niggling worries that I'd like to know whether they're real issues, or things I can ignore.
The way I connect my routes to my database is straight from the tutorials.
in app.js, this code instantiates the database, and attaches a reference to it to every req object that flows thru the middleware.
// wire up the database
var mongo = require('mongodb');
var db = require('monk')('localhost:27017/StarChamber');
----------8<-------
// Make our db accessible to our router
app.use(function(req,res,next){
req.db = db;
next();
});
And in the middleware it get used like this:
app.get('/', function (req, res) {
var db = req.db;
var collection = db.get('myCollection');
// do stuff to produce results
res.json (results);
});
So, to my niggling worries:
Passing the db to the routes by attaching it to the req is pretty convenient, but does it impact performance? Would it be better to have a reference to it in my router file that I could just use? What's the code to do this?
Is it good practice to drop the collection after its been used? The Tutorial doesn't do so, but a collection.drop() call before exiting the route handler looks beneficial, otherwise I think I'll just rack up lots of open connections with the db.
Thanks as ever!
No, it won't impact performance. It's a convenient method to pass a reference to db around, but with Monk it doesn't seem to be especially necessary. See below for an alternative setup.
You are confusing collections with connections. The former are the MongoDB-equivalent of "tables" in SQL, so dropping them doesn't seem to make sense since that would basically throw away all the data in your database table. As for connections: through various layers of indirection, Monk seems to be using the official MongoDB Node driver, which handles connections itself (by means of a connection pool). So there's no need to handle it yourself.
For an alternative way of passing the Monk database handle around: you can place it in a separate module:
// database.js
module.exports = require('monk')('localhost:27017/StarChamber');
And in each module where you require the handle, you can import it:
var db = require('./database');
I was coding using express js, and I noticed that I declared this in app.js
var mongoose = require ('mongoose');
var db =mongoose.connect('mongodb://localhost/testdb');
Then in my /models/userSchema.js
var mongoose = require('mongoose');
var users = mongoose.model('users',UserSchema);
module.exports = users;
However in my routes/upload.js
var mongoose = require ('mongoose');
var db =mongoose.connect('mongodb://localhost/testdb');`
//some code
mongoose.model('users').find();
// This knows that i am accessing the database called "testdb"
I am not sure why this works like how the code executing in upload.js and userSchema.js knows that the database i am using is testdb. Isn't this declaration of var mongoose = require('mongoose'); creates a new object separate from the one in app.js?
In node.js, modules loaded with require are cached so that calling require('mongoose') in two different files returns the same instance of the mongoose module.
So while variables from one file are not directly accessible in other files, variables within the same module are effectively shared between the files that require that module.
Mongoose is singleton. That is when you require it again you get the instance you first initialized.
App level variables are not visible in other modules. There are ways to pass the app object I tide modules though.
I am using mongodb-native-driver in express.js app. I have around 6 collections in the database, so I have created 6 js files with each having a collection as a javascript object (e.g function collection(){}) and the prototypes functions handling all the manipulation on those collections. I thought this would be a good architecture.
But the problem I am having is how to connect to the database? Should I create a connection in each of this files and use them? I think that would be an overkill as the connect in mongodb-native-driver creates a pool of connections and having several of them would not be justified.
So how do I create a single connection pool and use it in all the collections.js files? I want to have the connection like its implemented in mongoose. Let me know if any of my thought process in architecture of the app is wrong.
Using Mongoose would solve these problems, but I have read in several places thats it slower than native-driver and also I would prefer a schema-less models.
Edit: I created a module out of models. Each collection was in a file and it took the database as an argument. Now in the index.js file I called the database connection and kept a variable db after I got the database from the connection. (I used the auto-reconnect feature to make sure that the connection wasn't lost). In the same index.js file I exported each of the collections like this
exports.model1 = require('./model1').(db)
exprorts.model2 = require('./model2').(db)
This ensured that the database part was handled in just one module and the app would just call function that each model.js file exported like save(), fincdbyid() etc (whatever you do in the function is upto you to implement).
how to connect to the database?
In order to connect using the MongoDB native driver you need to do something like the following:
var util = require('util');
var mongodb = require('mongodb');
var client = mongodb.MongoClient;
var auth = {
user: 'username',
pass: 'password',
host: 'hostname',
port: 1337,
name: 'databaseName'
};
var uri = util.format('mongodb://%s:%s#%s:%d/%s',
auth.user, auth.pass, auth.host, auth.port, auth.name);
/** Connect to the Mongo database at the URI using the client */
client.connect(uri, { auto_reconnect: true }, function (err, database) {
if (err) throw err;
else if (!database) console.log('Unknown error connecting to database');
else {
console.log('Connected to MongoDB database server at:');
console.log('\n\t%s\n', uri);
// Create or access collections, etc here using the database object
}
});
A basic connection is setup like this. This is all I can give you going on just the basic description of what you want. Post up some code you've got so far to get more specific help.
Should I create a connection in each of this files and use them?
No.
So how do I create a single connection pool and use it in all the collections.js files?
You can create a single file with code like the above, lets call it dbmanager.js connecting to the database. Export functions like createUser, deleteUser, etc. which operate on your database, then export functionality like so:
module.exports = {
createUser: function () { ; },
deleteUser: function () { ; }
};
which you could then require from another file like so:
var dbman = require('./dbmanager');
dbman.createUser(userData); // using connection established in `dbmanager.js`
EDIT: Because we're dealing with JavaScript and a single thread, the native driver indeed automatically handles connection pooling for you. You can look for this in the StackOverflow links below for more confirmation of this. The OP does state this in the question as well. This means that client.connect should be called only once by an instance of your server. After the database object is successfully retrieved from a call to client.connect, that database object should be reused throughout the entire instance of your app. This is easily accomplished by using the module pattern that Node.JS provides.
My suggestion is to create a module or set of modules which serves as a single point of contact for interacting with the database. In my apps I usually have a single module which depends on the native driver, calling require('mongodb'). All other modules in my app will not directly access the database, but instead all manipulations must be coordinated by this database module.
This encapsulates all of the code dealing with the native driver into a single module or set of modules. The OP seems to think there is a problem with the simple code example I've posted, describing a problem with a "single large closure" in my example. This is all pretty basic stuff, so I'm adding clarification as to the basic architecture at work here, but I still do not feel the need to change any code.
The OP also seems to think that multiple connections could possibly be made here. This is not possible with this setup. If you created a module like I suggest above then the first time require('./dbmanager') is called it will execute the code in the file dbmanager.js and return the module.exports object. The exports object is cached and is also returned on each subsequent call to require('./dbmanager'), however, the code in dbmanager.js will only be executed the first require.
If you don't want to create a module like this then the other option would be to export only the database passed to the callback for client.connect and use it directly in different places throughout your app. I recommend against this however, regardless of the OPs concerns.
Similar, possibly duplicate Stackoverflow questions, among others:
How to manage mongodb connections in nodejs webapp
Node.JS and MongoDB, reusing the DB object
Node.JS - What is the right way to deal with MongoDB connections
As accepted answer says - you should create only one connection for all incoming requests and reuse it, but answer is missing solution, that will create and cache connection. I wrote express middleware to achieve this - express-mongo-db. At first sight this task is trivial, and most people use this kind of code:
var db;
function createConnection(req, res, next) {
if (db) { req.db = db; next(); }
client.connect(uri, { auto_reconnect: true }, function (err, database) {
req.db = db = databse;
next();
});
}
app.use(createConnection);
But this code lead you to connection-leak, when multiple request arrives at the same time, and db is undefined. express-mongo-db solving this by holding incoming clients and calling connect only once, when module is required (not when first request arrives).
Hope you find it useful.
I just thought I would add in my own method of MongoDB connection for others interested or having problems with different methods
This method assumes you don't need authentication(I use this on localhost)
Authentication is still easy to implement
var MongoClient = require('mongodb').MongoClient;
var Server = require('mongodb').Server;
var client = new MongoClient(new Server('localhost',27017,{
socketOptions: {connectTimeoutMS: 500},
poolSize:5,
auto_reconnect:true
}, {
numberOfRetries:3,
retryMilliseconds: 500
}));
client.open(function(err, client) {
if(err) {
console.log("Connection Failed Via Client Object.");
} else {
var db = client.db("theDbName");
if(db) {
console.log("Connected Via Client Object . . .");
db.logout(function(err,result) {
if(!err) {
console.log("Logged out successfully");
}
client.close();
console.log("Connection closed");
});
}
}
});
Credit goes to Brad Davley which goes over this method in his book (page 231-232)
Note: Please read the edited portion of this post before answering, it might save you time and answers one of my questions.
The problem I'm having is pretty simple but I'm pretty new to this overall and I'm having issues figuring out how to implement a mongodb database connection properly in a node/express app.
I'm using express 3.x and am basing my app layout around this project supplied by the author of Express:
https://github.com/expressjs/express/tree/d8caf209e38a214cb90b11ed59fd15b717b3f9bc/examples/blog (now removed from repo)
I have no interest in making a blog however the way the app is structured appears to be quite nice. The routes are separated and everything is organized nicely.
My problem is I might have 5-6 different route js files and each route js file might have anywhere between 1 and 15 routes; of those routes 1 or 15 might want to access the db.
So my problem is it seems like a really terrible idea to do a db.open(...) every single time I want to query the db. I should mention at this point I'm using the native mongo-db driver (npm install mongodb).
I would also need to include a file like this:
http://pastebin.com/VzFsPyax
...in all of those route files and all of my model files. Then I'm also dealing with dozens upon dozens of open connections.
Is there a way I can structure my app in such a way where I only make 1 connection and it stays open for the duration of the session (having a new one made every request would be bad too)?
If so, how can I do this? If you know the answer please post a code sample using tj's blog app (the one linked earlier in this post) structure as a base guide. Basically have a way where the routes and models can use the db freely while being in separate files than the db open code.
Thanks.
EDIT
I made some progress on solving one of my issues. If you look at tj's blog example he initializes his routes in the app.js like so:
require('./routes/site')(app);
require('./routes/post')(app);
And in the routes js file it starts like this:
module.exports = function(app){
I stumbled on a project earlier today where I saw someone pass 2 variables in the modules.exports call -> function(app, db). Then figured wow could it be that easy, do I need to just adjust my routes to be (app, db) too? Yeah, it seems so.
So now part 1 of the problem is solved. I don't have to require a mongo.js file with the connection boilerplate in every route file. At the same time it's flexible enough where I can decide to pick and choose which route files pass a db reference. This is standard and has no downside right?
Part 2 of the problem (the important one unfortunately) still exists though.
How can I bypass having to do a db.open(...) around every query I make and ideally only make a connection once per session?
Other solution is to pass database to the router via request, like this:
app.js
var db = openDatabase();
var app = express();
app.all('*', function(request, response, next)
{
request.database = db;
next();
});
app.get('/api/user/:id', Users.getByID);
users.js
var Users =
{
getByID: function(request, response)
{
request.database.collection('users').findOne(...)
response.send(user);
}
};
module.exports = Users;
I made a very simple module hub for this case that replaces the use of a global space.
In app.js you can create db connection once:
var hub = require('hub');
hub.db = new Db('foobar', new Server('10.0.2.15', 27017, {}), {native_parser: false});
And use it from any other files:
var hub = require('hub');
// hub.db - here link to db connection
This method uses a feature of 'require'. Module is only loaded for the first time and all the other calls gets a reference to an already loaded instance.
UPDATE
That's what I mean:
In main file like app.js we create Db connection, open it and store into hub:
app.js:
var hub = require('hub');
hub.mongodb = require('mongodb');
hub.mongodbClient = new hub.mongodb.Db('foobar', new hub.mongodb.Server('10.0.2.15', 27017, {}), {native_parser: false});
hub.mongodbClient.open(function(error) {
console.log('opened');
});
Now in any other file (message for example) we have access to opened connection and can simple use it:
message.js:
var hub = require('hub');
var collection = new hub.mongodb.Collection(hub.mongodbClient, 'message');
module.exports.count = function(cb) {
collection.count({}, function(err, count) {
cb(err, count);
});
};
Really silly. In the documentation it seems like db.open requires to be wrapped around whatever is using it, but in reality you can use it without a callback.
So the answer is to just do a db.open() in your database connection module, app.js file or where ever you decide to setup your db server/connection.
As long as you pass a reference to the db in the files using it, you'll have access to an "opened" db connection ready to be queried.