Nettle

On-the-fly processing framework for Node.js and MongoDB.

Install

npm install nettle

Stores

A store provides a simple interface to the GridFS entities in a MongoDB database. It provides basic put and get operations and allows the data to be arbitrarily processed.

var nettle = require('nettle');
var store = nettle.store({ db: 'example' });

Optionally specify host, port and collection prefix (defaults to 'fs') when creating a store.

Simple example of inserting a buffer into the store:

store.put(new Buffer('foo'), function(err, doc) {
    console.log(doc._id);
});

And later retrieving it:

store.get(id, function(err, buffer) {
    console.log(buffer.toString());
});

// -> 'foo'

Processing

A processor is an object with two properties: key and process. key must be a string (or a function that returns a string) and process must be a function accepting a buffer and callback. An example string processor might look something like this:

var Concat = function(str) {
    this.key = function() {
        return 'concat_' + str;
    },
    
    this.process = function(buffer, callback) {
        callback(null, new Buffer(buffer.toString() + str));
    }
};

var processor = new Concat('bar');

One can then retrieve processed entities by passing the processor to get:

store.get(id, processor, function(err, buffer) {
    console.log(buffer.toString());
});

// -> 'foobar'

Note that processed entities are stored and later retrieved by the given id and processor key. The process function will thus only be called on a cache miss.