HEAD HTTP requests in Rails 3

Question

Rails 3 currently routes a HEAD request to the matching GET route. There is a head? method on the request, but in returns false and the request acts like a get request. Can I detect if the request is a HEAD request?

Reasoning: I get that a HEAD request should return the EXACT same headers as the get, so Rails wants to perform the full GET and then shave off the body. However, I can conform to this request without issuing the same DB calls, etc that the GET would. Does this make sense?

Answer 1

I had this exact issue. It turns out that enabling caching causes this. Turn caching off in your environment and #head? will work as expected.

The issue is that Rack::Cache turns HEAD requests into GET requests so they can be cached. This is arguably the correct behavior, but it interfered with my application.

Answer 2

You can use the request.head? method to find out if it's a HEAD request:

http://api.rubyonrails.org/classes/ActionDispatch/Request.html#method-i-head-3F

Once you've determined that it is, you can also use the controller's head() method instead of the typical render:

http://guides.rubyonrails.org/layouts_and_rendering.html#using-head-to-build-header-only-responses

So I'd simply check request.head? before bothering with the database activities. Then use

head :ok, :custom_header => 'value'

Answer 3

def index
  if request.head?
    head :created
  else
    Rails.logger.info "Derp #{request.method}"
  end
end

Hmm. The above controller method works like I'd expect on Ruby v1.9.3-p194 and Rails v3.2.3; 201's w/o response body for the HEAD requests and 200's w/ for the GET's.