Are node.js module variables shared across multiple invocation? - variables

Question

i m creating a node.js server, where i have a "notifications" module. Every request on the node server will invoke this module and i need to have a set of private variables for each separate invocation.
For example, when a request is made to notifications module, it needs to remember the user id, request time, session id, etc.
How can i do that efficiently?
If i simple declare variables in module scope, they seem to be shared for each module invocation. So, it fails in remembering every request's data privately.
What i need is each time i invoke a node.js module, it will remember its data at that time. So, please point out how can i do that?
Thanks,
Anjan
Update
The node.js server is to uses as a chat server. the "notifications" module will scan the db for new messages and send the output in json format to the client using long polling technique.
I tried to wrap the data and the functions into an object. Then each time a request is made to chat server a new object will be created and it will carry on the desired functions. But what it did is that instead of working in parallel it executes each request in serial. So, if i make 3 request to the server, they just queue up and executes one after another.
Any clue on that?
The module source code can be found here: http://www.ultrasoftbd.com/notifications.js
Thanks,
Anjan

Answer 1

There are a couple ways that come to mind to approach this issue:
1) Have your module export a constructor which can be called by the API users of your module to give them a new instance of an object. This way, each user will have its own object instance which has its own private variables.
// Client example.
var mod = require('myModule')
, sess = new mod.Session();
sess.method(args);
sess.finalize();
2) Have your module provide a "registry" interface to these private variables which includes an identifier unique to the caller.
// Client example.
var mod = require('myModule');
var id = mod.initialize(); // Returns a unique ID.
mod.method(id, args); // Each method requires the ID.
mod.finalize(id);
These solutions share the idea that each instance (or ID) is tracked separately by your module so that the statistics (or whatever your module does) can be computed per client instance rather than globally to the module.