The definitions of #body in Rack::Response and ActionDispatch::Response are competing and causing performance problems with streaming responses. Rack::Response provides attr_accessor :body, while ActionDispatch::Response overrides that as follows:
def body str = '' each { |part| str << part.to_s } str end
This is problematic in instances where a streaming body is used, due to the definition of Rack::Response#close:
def close body.close if body.respond_to?(:close) end
Given these definitions, executing the Rack protocol on an ActionDispatch::Response instance (calling '#each', then '#close') causes the body to be enumerated twice -- once via the expected call to #each, and a second time via the call chain #close -> #body -> #each. See #4554 render :text => proc { ... } regression - Ruby on Rails - rails for a user report of this problem.
This could be fixed by using the instance variable directly:
def close @body.close if @body.respond_to?(:close) end
However, I think ActionDispatch::Response's #body override is dangerous and violates the principle of least surprise by removing the symmetry between #body and #body=. IMHO, it would be better to remove the override. If the concatenating behavior is necessary, supply a method named #body_text or a similar name that makes it clear that it disables streaming. This option causes numerous Rails test failures, however, as many tests are written to expect #body to return a string.
Thoughts?
