Comet app over REST in erlang ?

Question

Hi, I am a newbie to Erlang and am trying to make a switch to Erlang for our latest project. Since this is going to be a real-time chat (long polled) system for file sharing on the fly, I realized after a bit of digging around that Erlang would be the most appropriate choice, because of high concurrency, plus people also suggested to use Yaws since it can handle upto 50k parallel connections.

Although, it sounds awesome, but since I am a newbie (both to erlang and comet applications), I am unable to understand the right technology stack / architecture of how this would work. Also, because of relatively less documentation, I am unable to figure out how the individual pieces would fit together (web server, application layer, DB, message queue) for such an application. The application is going to run off a desktop client only (no web presence required), and so we need to build a REST api for the functionalities.

It would be great, if someone could point me in the right direction to proceed.

Thanks

Answer 1

You could use:

• ejabberd as the XMPP server
• mnesia as the database
• YAWS as the WEB server
• Message Queue : you can implement that in Erlang or use an enterprise solution such as RabbitMQ

Answer 2

The all new Zotonic application may inspire you. It's a webapp running off mochiweb for HTTP service with webmachine for the REST API. And it's using good ol' PostgreSQL as database.

It has comet support implemented.

Answer 3

Nitrogen has a very slick Comet feature built-in. It will work with the three most popular Erlang web servers, including the one you're already considering, YAWS.

Nitrogen doesn't do anything in particular about data storage. It's not one of those web frameworks that insists on managing the DB for you. You're free to use Mnesia or whatever else you like. If this bothers you, you might consider Erlyweb instead. It doesn't do Comet for you like Nitrogen does, but it's more of the manage-everything-for-me sort of web framework.