The ClojureWerkz Blog

News and updates about ClojureWerkz projects

Introducing Machine Head

Why Messaging Matters for Emerging Languages

Over the last 6-7 years we have been observing how companies adopt emerging technologies. Younger languages such as Clojure may enjoy completely green field projects every now and then, but most of the time, they have to integrate into existing systems.

Back when ClojureWerkz “founders” started adopting Clojure, the very first project we had to develop was Langohr. Langohr is a RabbitMQ client that made it possible for us to build services in Clojure that interoperate with other applications (in Ruby and C). That worked very well and messaging keeps being one of our primary integration strategies.

Today we are happy to announce another project in the same space: Machine Head.

What is Machine Head

Machine Head is a minimalistic Clojure MQTT (v3.1) client built on top of Eclipse Paho.

MQTT is an efficient messaging protocol that was designed for low power devices like sensors. It is quite useful as a general purpose protocol, despite being small in scope.

Machine Head is a project for developers who want to integrate Clojure-based services into a system that involves telemetry devices and would prefer to keep the same protocol across the system. So it’s not a replacement for Langohr but a complimentary library. Indeed, RabbitMQ 3.x supports MQTT so you can use both with it!

Documentation and Examples

To get started with Machine Head, please refer to our Getting Started guide. The rest of the documentation is work in progress.

To give you a taste of what using Machine Head is like, here’s a Hello, World example:

(ns clojurewerkz.machine-head.examples.hello-world
  (:require [clojurewerkz.machine-head.client :as mh]))

(defn -main
  [& args]
  (let [id   (mh/generate-id)
        conn (mh/connect "tcp://" id)]
    (mh/subscribe conn ["hello"] (fn [^String topic meta ^bytes payload]
                                   (println (String. payload "UTF-8"))
                                   (mh/disconnect conn)))
    (mh/publish conn "hello" "Hello, world")))

Supported Clojure Versions

Machine Head targets Clojure 1.5+, tested against 3 Clojure versions x 2 JDKs on, and is released under the Eclipse Public License.


To subscribe for announcements of releases, important changes and so on, please follow @ClojureWerkz on Twitter.


The source is available on GitHub. We also use GitHub to track issues.

The ClojureWerkz Team