Pub/sub for Node.js and MongoDB

Mubsub is a pub/sub implementation for Node.js and MongoDB. It utilizes Mongo's capped collections and tailable cursors to notify subscribers of inserted documents that match a given query.

var mubsub = require('mubsub');
var client = mubsub('mongodb://localhost:27017/mubsub_example');
var channel ='test');
client.on('error', console.error);
channel.on('error', console.error);
channel.subscribe('bar', function (message) {
    console.log(; // => 'bar' 
channel.subscribe('baz', function (message) {
    console.log(message); // => 'baz' 
channel.publish('bar', { foo: 'bar' });
channel.publish('baz', 'baz');

You can pass a Db instance or a URI string. For more information about the URI format visit

var mubsub = require('mubsub');
// Using a URI 
var client = mubsub('mongodb://localhost:27017/mubsub_example', [options]);
// Passing a MongoDB driver `Db` instance directly. 
var client = mubsub(new Db(...));

A channel maps one-to-one with a capped collection (Mubsub will create these if they do not already exist in the database). Optionally specify the byte size of the collection and/or the max number of documents in the collection when creating a channel.

WARNING: You should not create lots of channels because Mubsub will poll from the cursor position.

var channel ='foo', { size: 100000, max: 500 });


  • size max size of the collection in bytes, default is 5mb
  • max max amount of documents in the collection
  • retryInterval time in ms to wait if no docs are found, default is 200ms
  • recreate recreate the tailable cursor when an error occurs, default is true

WARNING: Don't remove collections with running publishers. It's possible for mongod to recreate the collection on the next insert (before Mubsub has the chance to do so). If this happens the collection will be recreated as a normal, uncapped collection.

var subscription = channel.subscribe([event], callback);

Subscriptions register a callback to be called whenever a document matching the specified event is inserted (published) into the collection (channel). You can omit the event to match all inserted documents. To later unsubscribe a particular callback, call unsubscribe on the returned subscription object:

channel.publish(event, obj, [callback]);

Publishing a document simply inserts the document into the channel's capped collection. A callback is optional.

The following events will be emitted:

// The given event was published 
channel.on('myevent', console.log);
// Any event was published 
channel.on('message', console.log);
// Document was inserted 
channel.on('document', console.log);
// Mubsub is ready to receive new documents 
channel.on('ready', console.log);
// Connection error 
client.on('error', console.log);
// Channel error 
channel.on('error', console.log);

Closes the MongoDB connection.

npm install mubsub
make test

You can optionally specify the MongoDB URI to be used for tests:

MONGODB_URI=mongodb://localhost:27017/mubsub_tests make test
  • simpleio Simple long polling based communication.