rails_example_for_nginx_cache.rb

#in controller:
before_action :resourceful_cache_headers
before_action :resourceless_cache_headers
before_action :skip_session

def skip_session
  # if you need to deliver flash, or authencity token, or you explicitly need session
  request.session_options[:skip] = true unless you_need_session
end

def resourceless_cache_headers
  # if you serving resourceless pages, you must specify template explicitly, or
  # you'll get yourself default etag from rack, meaning actually not so conditional GET. 
  fresh_when( nil, template: "#{controller_path}/#{action_name}" )
end

def resourceful_cache_headers
  # if resource isn't nil, the template: "#{controller_path}/#{action_name}", may be ommited
  fresh_when( @resource )
end

#in controller for actions from forms which can be send from cached pages:
skip_before_action :verify_authenticity_token, only: [:create]

# also may be better to remove csrf token from layout of cached pages
# don't forget than any kind of set cookies will pass cache,
# be aware that some gems can do this for you, like, for instance, rack-mini-profiler,
# It's reasonable NOT to interfere Set-Cookie on NGINX layer,
# because Nginx can't be sure intended or not this behaviour