qlobber

What is qlobber?

The qlobber npm package is a fast and flexible topic-based publish/subscribe library for Node.js. It allows you to match topics to subscribers using a trie-based approach, which is efficient and scalable. This package is particularly useful for implementing message brokers, event emitters, and other pub/sub systems.

What are qlobber's main functionalities?

Basic Topic Matching

This feature allows you to add topics and match them against patterns. The code sample demonstrates how to add topics and retrieve matches for specific topics.

const Qlobber = require('qlobber').Qlobber;

let matcher = new Qlobber();
matcher.add('foo.*', 'it matches foo.bar');
matcher.add('foo.*', 'it also matches foo.baz');
matcher.add('foo.bar', 'it matches foo.bar exactly');

console.log(matcher.match('foo.bar')); // ['it matches foo.bar', 'it matches foo.bar exactly']
console.log(matcher.match('foo.baz')); // ['it also matches foo.baz']

Removing Topics

This feature allows you to remove specific topics from the matcher. The code sample demonstrates how to add and then remove a topic, showing the updated matches.

const Qlobber = require('qlobber').Qlobber;

let matcher = new Qlobber();
matcher.add('foo.*', 'it matches foo.bar');
matcher.add('foo.bar', 'it matches foo.bar exactly');

matcher.remove('foo.bar', 'it matches foo.bar exactly');

console.log(matcher.match('foo.bar')); // ['it matches foo.bar']

Wildcard Matching

This feature supports wildcard matching using '*' and '#' symbols. The code sample demonstrates how to use wildcards to match multiple topics.

const Qlobber = require('qlobber').Qlobber;

let matcher = new Qlobber();
matcher.add('foo.*', 'it matches foo.bar');
matcher.add('foo.#', 'it matches foo.bar and foo.baz');

console.log(matcher.match('foo.bar')); // ['it matches foo.bar', 'it matches foo.bar and foo.baz']
console.log(matcher.match('foo.baz.qux')); // ['it matches foo.bar and foo.baz']

Other packages similar to qlobber

mqtt

The mqtt package is a client library for the MQTT protocol, which is a lightweight messaging protocol for small sensors and mobile devices. It provides similar pub/sub functionality but is more focused on network communication and IoT applications. Unlike qlobber, mqtt is protocol-specific and includes features for connecting to MQTT brokers.

eventemitter2

The eventemitter2 package is an enhanced version of Node.js's EventEmitter class. It provides advanced features like wildcard event names, which are similar to qlobber's topic matching. However, eventemitter2 is more general-purpose and is used for event handling within applications rather than for message brokering.

postal

The postal package is a JavaScript library for pub/sub messaging. It offers similar topic-based subscription and publication features. Postal is more focused on in-app messaging and provides additional features like message channels and middleware, making it more versatile for complex applications compared to qlobber.

README

qlobber   

Node.js globbing for amqp-like topics.

Example:

Qlobber = require('qlobber').Qlobber;
matcher = new Qlobber();
matcher.add('foo.*', 'it matched!');
assert.deepEqual(matcher.match('foo.bar'), ['it matched!']);

The API is described here.

qlobber is implemented using a trie, as described in the RabbitMQ blog posts here and here.

Installation

npm install qlobber

Another Example

A more advanced example using topics from the RabbitMQ topic tutorial:

matcher = new Qlobber({ remove_duplicates: true });
matcher.add('*.orange.*', 'Q1');
matcher.add('*.*.rabbit', 'Q2');
matcher.add('lazy.#', 'Q2');
assert.deepEqual(['quick.orange.rabbit',
                  'lazy.orange.elephant',
                  'quick.orange.fox',
                  'lazy.brown.fox',
                  'lazy.pink.rabbit',
                  'quick.brown.fox',
                  'orange',
                  'quick.orange.male.rabbit',
                  'lazy.orange.male.rabbit'].map(function (topic)
                  {
                      return matcher.match(topic).sort();
                  }),
                 [['Q1', 'Q2'],
                  ['Q1', 'Q2'],
                  ['Q1'],
                  ['Q2'],
                  ['Q2'],
                  [],
                  [],
                  [],
                  ['Q2']]);

Licence

MIT

Tests

qlobber passes the RabbitMQ topic tests (I converted them from Erlang to Javascript).

To run the tests:

grunt test

Lint

grunt lint

API

Source: lib/qlobber.js

• Qlobber
• Qlobber.prototype.add
• Qlobber.prototype.remove
• Qlobber.prototype.match
• Qlobber.prototype.clear

Qlobber([options])

Creates a new qlobber.

Parameters:

• {Object} [options] Configures the qlobber. Use the following properties:

  • {String} separator The character to use for separating words in topics. Defaults to '.'. MQTT uses '/' as the separator, for example.

  • {String} wildcard_one The character to use for matching exactly one word in a topic. Defaults to '*'. MQTT uses '+', for example.

  • {String} wildcard_some The character to use for matching zero or more words in a topic. Defaults to '#'. MQTT uses '#' too.

  • {Boolean} remove_duplicates qlobber's matching algorithm means values may be returned twice. Specify true to have qlobber remove duplicates from its results. Note this will incur a performance penalty. Defaults to false.

_{Go: TOC}

Qlobber.prototype.add(topic, val)

Add a topic matcher to the qlobber.

Note you can match more than one value against a topic by calling add multiple times with the same topic and different values.

Parameters:

• {String} topic The topic to match against.
• {Any} val The value to return if the topic is matched. undefined is not supported.

_{Go: TOC | Qlobber.prototype}

Qlobber.prototype.remove(topic, [val])

Remove a topic matcher from the qlobber.

Parameters:

• {String} topic The topic that's being matched against.
• {Any} [val] The value that's being matched. If you don't specify val then all matchers for topic are removed.

_{Go: TOC | Qlobber.prototype}

Qlobber.prototype.match(topic)

Match a topic.

Parameters:

• {String} topic The topic to match against.

Return:

{Array} List of values that matched the topic. This may contain duplicates unless you configured Qlobber otherwise.

_{Go: TOC | Qlobber.prototype}

Qlobber.prototype.clear()

Reset the qlobber.

Removes all topic matchers from the qlobber.

_{Go: TOC | Qlobber.prototype}

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