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:
