Pre-building view cache in Rails - ruby-on-rails

Question

Is there a way to pre-build a page cache without calling the actual page via a http request?
I looked at solutions like this and this, but these don't generate the cache.
I have a relatively complicated view, and want to cache the entire thing. I want to pre-build this cached version in the application so when a user actually hits it, it will already be there.
Thanks

Answer 1

We had a need to do something similar from a rake task -- we had a partial that would need to display a very long list of entities (~700) which were somewhat context specific and which, due to a series of database structure issues and custom sorting criteria, would easily take > 25 seconds to render the first time before going into cache> This would often time out because our HTTP servers were set to terminate HTTP requests with no response after 30 seconds, and pre-caching this custom list was a solution.
What you need to do is create an instance of ActiveController::Base, or of one of your controllers if you need helper methods or other entities, then pass its lookup_context reference to a new instance of ActionView.Renderer.
In our rake task, we did the following
namespace :rake_for_time_consuming_nonsense do
task :pre_cache_long_list do
PreCacher.pre_fetch_partials
end
end
class PreCacher
def self.pre_fetch_partials
the_controller = ActionController::Base.new
# Set any instance variables required by your partial in the controller,
# they will be passed to the partial with the view_context reference
the_controller.instance_variable_set "#cache_key", cache_key
the_controller.instance_variable_set "#the_object", MyModel.first
view_renderer = ActionView::Renderer.new the_controller.lookup_context
view_renderer.render the_controller.view_context, {partial: 'my_model/the_partial', layout: false}
end
end
This works in Rails 3.2.13.

Answer 2

I think following link should give you a good start.
How do I get the rendered output of a controller's action without visiting the web page?
I try to accomplish the same and as far i can see, your fake request should have the correct host, because the cache-key includes host informations.
I accomplished caching by using ActionController::Integration::Session
ais = ActionController::Integration::Session.new
ais.host = host
ais.xml_http_request(:post, url, params, headers)
I'v got another one:
class FakeRequest
include ActionController::UrlWriter
def initialize(url, params, session, host)
#url = url
#params = params
#session = session
default_url_options[:host] = URI.parse(host).host
end
def post
process(:post)
end
def get
process(:get)
end
def xhr
process(:post, true)
end
def process(method, ajax = false)
uri = URI.parse(url_for(#url))
request = ActionController::TestRequest.new({'HTTP_HOST' => uri.host,'rack.input' => '','rack.url_scheme' => 'http'})
request.query_parameters = #params
request.path = uri.path
request.host = uri.host
request.env['REQUEST_METHOD'] = method.to_s.upcase
if ajax
request.headers['X-Requested-With'] = 'XMLHttpRequest'
end
#session.each_pair do |k,v|
request.session[k] = v
end
response = ActionController::TestResponse.new
controller = ActionController::Routing::Routes.recognize(request).new
return controller.process(request, response)
end
end
This will also return the response object.