Incrementing resource counter in a RESTful way: PUT vs POST

Question

I have a resource that has a counter. For the sake of example, let\'s call the resource profile, and the counter is the number of views

Answer 1

I think the right answer is to use PATCH. I didn't see anyone else recommending it should be used to atomically increment a counter, but I believe RFC 2068 says it all very well:

The PATCH method is similar to PUT except that the entity contains a list of differences between the original version of the resource identified by the Request-URI and the desired content of the resource after the PATCH action has been applied. The list of differences is in a format defined by the media type of the entity (e.g., "application/diff") and MUST include sufficient information to allow the server to recreate the changes necessary to convert the original version of the resource to the desired version.

So, to update profile 123's view count, I would:

PATCH /profiles/123 HTTP/1.1
Host: www.example.com
Content-Type: application/x-counters

views + 1

Where the x-counters media type (which I just made up) is made of multiple lines of field operator scalar tuples. views = 500 or views - 1 or views + 3 are all valid syntactically (but may be forbidden semantically).

I can understand some frowning-upon making up yet another media type, but I humbly suggest it's more correct than the POST / PUT alternative. Making up a resource for a field, complete with its own URI and especially its own details (which I don't really keep, all I have is an integer) sounds wrong and cumbersome to me. What if I have 23 different counters to maintain?