Monitoring Mongo for changes with Node.js

Question

I'm using Node.js for some project work and I would like to monitor my Mongo database (collection) for changes, basically fire an event if something gets added.

Anyone know if this is possible? I'm using the node-mongodb-native drivers.

If it's not I'd also like any available pointers on pushing data from the server (run with node) to the client browser.

Answer 1

The question is if all data is added to your database through your node.js app. If so, you can use the EventEmitter class of node.js to trigger an event (http://nodejs.org/api.html#eventemitter-14).

If the database is populated by some other app, things are getting difficult. In this case you would need something like a database trigger, which is AFAIK not yet availabled in MongoDB.

Pushing Events to the Client (aka Comet) will be possible once the HTML 5 websockets API makes its way into all major browsers.

In the meantime, you can only try to emulate this behaviour using techniques like (long-term) AJAX polling, forever frame etc. but each of them has its weaknesses.

Answer 2

I would turn on replication in your mongodb. There is a replicate? database that contains a list of changes, similar to the mysql replication log. You can monitor that.

-daniel