Pubsub.io

a query based client/server publish subscribe protocol built on node.js.

Client implementions currently exists for the browser and node.js.

// to connect in node.js do:
var pubsub = require('pubsub.io').connect('hub.pubsub.io');

// to connect in the browser do:
var pubsub = pubsub.connect('hub.pubsub.io');

pubsub.subscribe({}, function(doc) {
	console.log('someone published', doc);
});

pubsub.publish({foo:'bar'});

Try running this yourself

The client library is hosted at http://pubsub.io/pubsub.io.js

The nodejs library is available through npm. npm install pubsub.io

Publish

Whenever you want to send documents to other pubsub clients you need to publish it. The published document is then received by all subscribers whose query match the document.

pubsub.publish({name: 'pubsub', authors: ['mathias', 'ian'], version: 0.1});

Subscribe

Whenever you want to receive documents from other pubsub clients you need to create a subscription with a query. The subscription is evaluated at the hub against all documents as they are published, if the query matches the published document your subscription handler will invoked with the document.

pubsub.subscribe({name: 'pubsub', version: {$gt:0}}, function(doc) {
	console.log('i love',doc);
});

You can choose to filter the document with a selction.

pubsub.subscribe(query, {property1:1, property2:1}, function(doc){
	console.log(doc); // will only contain the selected properties
});

Unsubscribe

In order to unsubscribe a subscription, you call the function returned when subscribing

var sub = pubsub.subscribe({foo:'bar'},function(doc) {
	console.log(doc);
}); // creates the subscription

sub(); // removes the subscription

Token and authentication

As a subscriber you can use authentication to make sure that you can trust the data you subscribe to. In order to do this the publisher must provide signed 'authenticated' properties. The signed properties are provided by the token.

As a publisher you can use authentication to limit the subscribers by the data by demanding that they use signed properties in their subscription queries.

var token = ... get authtoken from you authentication enpoint
// in order for the hub to verifed the signed token it need to share key with the authentication enpoint

// we subscribe as a signed user so publishers can trust us
pubsub.subscribe({to: token.user, from: {$authenticated:'user',value:'transmitter'}}, function(doc) {
	// the doc.from was authenticated as a user, the doc can therefore be trusted
});

// we want to limit the subscribers to authenticated users only
pubsub.publish({to: {$authenticated:'user', value:'receiver'},from: token.user});

The Query Language

The query language syntax is derived from the query language of mongodb.
In general any property of a query that is not a language property represents a === relation, except if it is a regex - it is then the same as a $regex relation.

The language consists of 2 parts. The outer language {$outer:...} and the inner language {prop:{$inner:...}}.

The outer language

$has: key(s) checks if the document has the given keys. multiple has an and relation $or: [paths] define multiple query paths

var query = {
	$or: [{
		name:'pubsub.io' // check where the name is pubsub.io
	}, {
		{$has:'alias'}   // or wether it has a property called alias
	}]
};

The inner language

$exists: bool checks if the given property exists
$nil: bool is undefined or null

var query = {
	name: {$nil:false},   // will reject if name is null or undefined
	coupling: {$exists:false} // document must not have a property called coupling
};

$any: value(s) is equal to any of the values
$regex: regex must match regex
$like: substr property must have a substring which is case-insensitive equal to substr

var query = {
	name: {$any:['mathias', 'ian']},  // name must be equal to either mathias or ian
	project: /pubsub\.io/i            // project should have a substring pubsub.io in any case
};

$gt: num must be strictly greater than the num
$gte: num must be greater or equal than the num
$lt: num must be strictly lower than the num
$lte: num must be lower or equal than the num
$mod: [base,val] same as property % base === val

var query = {
	age: {$gt:20, $lte:40, $mod:[2,0]} // only match even ages between 20+ and 40		
};

$distance: circle check if point is within a circle {lat:0,lon:0} with radius 800 km|m|mi|yd|ft

var query = {point: {$distance: {center: {lat:0,lon:0}, radius:'800 km'}}};

$datetime: pattern query against dates. Pattern format: day? date? month? year? hour:minute:second e.g. Monday 22 August 2011 10:30:01

var query = {
	time : {$datetime: 'monday 2011'} // matches dates on mondays in 2011
};

var query = {
	time : {$datetime: '10:30:00'} // matches dates every day at 10:30:00 am 
};

var query = {
	time : {$datetime : '10:--:--'} // matches dates every day at 10 for the entire hour 
};

$not: value must not be equal to value or match value if it is a regex

All language properties can be negated by putting $not in front of it, i.e. $notnil checks if a property is different from undefined and null

var query = {
	friend: {$notlike:'nemesis'} // our friend must not contain the substring nemesis
};

LICENSE

Copyright (c) 2011 Ian Jørgensen [email protected] and Mathias Buus Madsen [email protected]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.