Mongoose + Express - What's the proper way to save the user in the document (audit info)

Question

Mongoose + Express - What's the proper way to save the user in the document (audit info)

I'm writing an Express.js app that uses Mongoose ODM. When a document is created/updated, I want it to automatically get some fields populated:

createdBy
createdOn

It seems to me that the right place to implement that would be in a Mongoose plugin that augments the document with those properties and provides defaults and/or mongoose middleware to populate the fields.

However, I have absolutely no idea how I could get the username from the session in my plugin. Any suggestion?

/**
 * A mongoose plugin to add mandatory 'createdBy' and 'createdOn' fields.
 */
 module.exports = exports = function auditablePlugin (schema, options) {
   schema.add({
     createdBy: { type: String, required: true, 'default': user }
   , createdOn: { type: Date, required: true, 'default': now }
   });
 };

 var user = function(){
   return 'user'; // HOW to get the user from the session ???
 };

 var now = function(){
   return new Date;
 };

node.js
express
mongoose

Answer 1

You can't do this like this, bacause user function is added as a prototype method for this schema. In particular it is request/response independent. There is a hack however. If you have object obj of the type schema, then you can do

obj.session = req.session;

in request handler. Then you can access the session from the function. However this may lead to other issues ( for example running cron jobs on this collection ) and it looks like a very bad practice to me.

You can just do that manually, when a current user creates this schema object, can't you? Or create static method:

MySchema.statics.createObject = function ( user ) {
    // create your object
    var new_object = MySchema( ... );
    // set necessary fields
    new_object.createdBy = user.username;
}