Pub/sub for Node.js and MongoDB

npm install mubsub
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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. You should not create lots of channels, because mubsub will poll from the cursor position.


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');


Create a client

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

var mubsub = require('mubsub');

// Using uri
var client = mubsub('mongodb://localhost:27017/mubsub_example', [options]);

// Pass 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 or/and max number of documents in the collection when creating a channel.

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 found, default is 200ms
  • recreate recreate the tailable cursor on error, default is true

Don't remove collections with running publishers. Mongod can recreate the collection on insert automatically before mubsub will do it and without capped = true.


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. Callback is optional.

Listen to events

Following events will be emitted:

    // Subscribe to some specicific event, like channel.subscribe
    channel.on('myevent', console.log);

    // Subscribe to a "message"
    channel.on('message', console.log);

    // Subscribe to "document" event to get the entire mongo document.
    channel.on('document', console.log);

    // Mubsub is ready to receive new documents.
    channel.on('ready', console.log);

    // Connection errors
    client.on('error', console.log);

    // Channel errors
    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

Projects using mubsub

  • simpleio Simple long polling based communication.
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