I've been working quite a bit with RESTful webservices and MQTT recently. One annoying gap of REST interfaces is there's no clear / simple / natural way to work notifications into the paradigm. For example, consider this resource
This is very well behaved from a REST point of view. It can handle GET and PUT (and I think PATCH) requests to retrieve and modify state. However, if the state is modified, how does someone else know this in near real time? Well, MQTT is a natural solution, but the way a developer would know this is to "read the docs". Reading the docs kinda sucks if you can make it Just Work.
For discussion, I'm proposing a rel="mqtt" Link type that can bind REST resources to an MQTT server. For example, if you look at that resource above:
HTTP/1.1 200 OK
Date: Sat, 05 Jul 2014 14:36:37 GMT
Server: Apache/2.2.25 (Unix) DAV/2 PHP/5.2.16 mod_ssl/2.2.25 OpenSSL/0.9.8e-fips-rhel5 mod_fastcgi/2.4.6
Access-Control-Allow-Methods: GET, PUT, POST
The Link: header says that there's an associated MQTT resource available, that broadcasts updates (payload=PUT) in JSON (the default content-type) using the topic "basement/hue/1". Deeper documentation is available here:
And a really lousy diagram of what this looks like right here:
Your feedback is appreciated.