Node.js, Express and Postgres design - node.js

Question

I am creating an API with Node.js and Express. I'm using Postgres as DB.
I would like to create a "global object", called DBConn or something, that I can access from everywhere in the App. This object would have the functions for inserting, updating, validating, etc.
How would be the general architecture in Node and Express for this to work? Does it make sense in Node to instantiate it just once and keep the communication with the DB open, or should I instantiate it everytime I want to perform a DB action?

Answer 1

Here's everything that you are looking for, using pg-promise:
// Users repository:
var repUsers = function (obj) {
return {
add: function (name) {
return obj.none("insert into users(name) values($1)", name);
},
delete: function (id) {
return obj.none("delete from users where id=$1", id);
}
// etc...
};
};
var options = {
extend: function () {
// extending the protocol:
this.users = repUsers(this);
}
};
var pgp = require('pg-promise')(options);
var cn = "postgres://username:password#host:port/database";
var db = pgp(cn); // your global database instance;
db.users.add("John")
.then(function () {
// success;
})
.catch(function (error) {
// error;
});
This will also manage your database connection automatically, you will just keep using variable db throughout your application.
And setting up a repository is optional, you can always use in-line queries instead. See the library for details and more examples.

Answer 2

I don't know Postgres at all,but maybe you can try this:
Create a file named 'DBConn.js' in YourApp/common directory.
DBConn.js:
var DBConn = exports = modules.exports = {}
//code to connect to database
....
//insert update detele select
DBConn.insert = function(arguments) {
//some code
}
.....
DBConn.update = function(arguments) {
//some code
}
Then you can require it in any other controller like YouApp/controller/UserController.js
UserController.js:
var DBConn = require('../common/DBConn.js')
Example of module cache
index.js:
require('./DB.js');
require('./DB.js');
DB.js
var DB = exports = module.exports = {}
function connect() {
//connect to database code
console.log('Connect!');
}
connect();
//other code
Then node index.js,we can see that 'Connect!' only logged once.
Because when we first require('DB.js'),node.js put it to the module cache,and when we require DB.js again,we get DB.js from cache.