Steve Vinoski’s Blog

Nick Gerakines has posted a detailed example of a RESTful web service implemented using Erlang and Yaws. It provides a lot of implementation information that I didn’t have room for in my InfoQ article on this topic.

Sam’s issue isn’t addressed here either, but no matter, the details of Nick’s example are worth examining nonetheless.

Regarding my “RESTful Services with Erlang and Yaws” article on InfoQ.com, Sam Ruby said:

This otherwise excellent article fails my ETag test.

When Sam speaks, I listen, so I’ve given his feedback a lot of thought.

As I wrote in a comment on Sam’s blog, the Erlang/Yaws RESTful services I work on do indeed support conditional GETs, so at least my day-to-day work passes his ETags test. As for the article, there are two ways to think about it:

1. If you focus on the “RESTful Design” portion of the article, then yes, I could have added a “think about where you need to support conditional GETs” item to the “key areas to pay attention to” list.

2. If you focus on the Yaws/Erlang aspect of the article, then keep in mind that dealing with ETags requires dealing with HTTP headers such as If-none-match and the ETag header itself. The article already shows you how to read request headers and write reply headers, though, and how you actually create specific ETag values for use in the headers depends on the particulars of your resources — Leonard Richardson’s and Sam’s excellent book already covers this pretty well.

I intended the focus of the article to be more about item 2 than item 1, so I think not specifically addressing ETags is OK.

One thing I should have included, though, is how to parse POST data. You use the yaws_api:parse_post/1 function for that, passing in an arg record. For typical form data, it’ll give you back a list of key/value pairs over which you can iterate, or from which you can extract expected key/value pairs using yaws_api:postvar/2 (or even proplists:lookup/2 or lists:keysearch/3, if you like). See the documentation at the Yaws website for more details, but all in all, handling POST data in Yaws is fairly trivial.

Today InfoQ.com published a new article I’ve written entitled “RESTful Services with Erlang and Yaws.” Stefan Tilkov recently asked me if I had anything to contribute to InfoQ, and I thought an article on that topic might be interesting, as I hadn’t before seen anything covering REST and Erlang together.

I think it’s one of those articles that could be much, much longer and far more detailed if space (and time) permitted, but hopefully there’s enough there to whet your appetite if you’re considering developing RESTful web services in Erlang. I really can’t say enough good things about using Erlang and Yaws for this purpose — it’s quite a solid platform.

I’ll be giving a talk on the same topic at both JAOO Brisbane and JAOO Sydney at the end of May and beginning of June, respectively.