# frozen_string_literal: true
require "active_support/core_ext/object/try"
require "active_support/core_ext/integer/time"
module ActionController
module ConditionalGet
extend ActiveSupport::Concern
include Head
included do
class_attribute :etaggers, default: []
end
module ClassMethods
# Allows you to consider additional controller-wide information when generating an ETag.
# For example, if you serve pages tailored depending on who's logged in at the moment, you
# may want to add the current user id to be part of the ETag to prevent unauthorized displaying
# of cached pages.
#
# class InvoicesController < ApplicationController
# etag { current_user&.id }
#
# def show
# # Etag will differ even for the same invoice when it's viewed by a different current_user
# @invoice = Invoice.find(params[:id])
# fresh_when(@invoice)
# end
# end
def etag(&etagger)
self.etaggers += [etagger]
end
end
# Sets the +etag+, +last_modified+, or both on the response and renders a
# <tt>304 Not Modified</tt> response if the request is already fresh.
#
# === Parameters:
#
# * <tt>:etag</tt> Sets a "weak" ETag validator on the response. See the
# +:weak_etag+ option.
# * <tt>:weak_etag</tt> Sets a "weak" ETag validator on the response.
# Requests that set If-None-Match header may return a 304 Not Modified
# response if it matches the ETag exactly. A weak ETag indicates semantic
# equivalence, not byte-for-byte equality, so they're good for caching
# HTML pages in browser caches. They can't be used for responses that
# must be byte-identical, like serving Range requests within a PDF file.
# * <tt>:strong_etag</tt> Sets a "strong" ETag validator on the response.
# Requests that set If-None-Match header may return a 304 Not Modified
# response if it matches the ETag exactly. A strong ETag implies exact
# equality: the response must match byte for byte. This is necessary for
# doing Range requests within a large video or PDF file, for example, or
# for compatibility with some CDNs that don't support weak ETags.
# * <tt>:last_modified</tt> Sets a "weak" last-update validator on the
# response. Subsequent requests that set If-Modified-Since may return a
# 304 Not Modified response if last_modified <= If-Modified-Since.
# * <tt>:public</tt> By default the Cache-Control header is private, set this to
# +true+ if you want your application to be cacheable by other devices (proxy caches).
# * <tt>:template</tt> By default, the template digest for the current
# controller/action is included in ETags. If the action renders a
# different template, you can include its digest instead. If the action
# doesn't render a template at all, you can pass <tt>template: false</tt>
# to skip any attempt to check for a template digest.
#
# === Example:
#
# def show
# @article = Article.find(params[:id])
# fresh_when(etag: @article, last_modified: @article.updated_at, public: true)
# end
#
# This will render the show template if the request isn't sending a matching ETag or
# If-Modified-Since header and just a <tt>304 Not Modified</tt> response if there's a match.
#
# You can also just pass a record. In this case +last_modified+ will be set
# by calling +updated_at+ and +etag+ by passing the object itself.
#
# def show
# @article = Article.find(params[:id])
# fresh_when(@article)
# end
#
# You can also pass an object that responds to +maximum+, such as a
# collection of active records. In this case +last_modified+ will be set by
# calling <tt>maximum(:updated_at)</tt> on the collection (the timestamp of the
# most recently updated record) and the +etag+ by passing the object itself.
#
# def index
# @articles = Article.all
# fresh_when(@articles)
# end
#
# When passing a record or a collection, you can still set the public header:
#
# def show
# @article = Article.find(params[:id])
# fresh_when(@article, public: true)
# end
#
# When rendering a different template than the default controller/action
# style, you can indicate which digest to include in the ETag:
#
# before_action { fresh_when @article, template: 'widgets/show' }
#
def fresh_when(object = nil, etag: nil, weak_etag: nil, strong_etag: nil, last_modified: nil, public: false, template: nil)
weak_etag ||= etag || object unless strong_etag
last_modified ||= object.try(:updated_at) || object.try(:maximum, :updated_at)
if strong_etag
response.strong_etag = combine_etags strong_etag,
last_modified: last_modified, public: public, template: template
elsif weak_etag || template
response.weak_etag = combine_etags weak_etag,
last_modified: last_modified, public: public, template: template
end
response.last_modified = last_modified if last_modified
response.cache_control[:public] = true if public
head :not_modified if request.fresh?(response)
end
# Sets the +etag+ and/or +last_modified+ on the response and checks it against
# the client request. If the request doesn't match the options provided, the
# request is considered stale and should be generated from scratch. Otherwise,
# it's fresh and we don't need to generate anything and a reply of <tt>304 Not Modified</tt> is sent.
#
# === Parameters:
#
# * <tt>:etag</tt> Sets a "weak" ETag validator on the response. See the
# +:weak_etag+ option.
# * <tt>:weak_etag</tt> Sets a "weak" ETag validator on the response.
# Requests that set If-None-Match header may return a 304 Not Modified
# response if it matches the ETag exactly. A weak ETag indicates semantic
# equivalence, not byte-for-byte equality, so they're good for caching
# HTML pages in browser caches. They can't be used for responses that
# must be byte-identical, like serving Range requests within a PDF file.
# * <tt>:strong_etag</tt> Sets a "strong" ETag validator on the response.
# Requests that set If-None-Match header may return a 304 Not Modified
# response if it matches the ETag exactly. A strong ETag implies exact
# equality: the response must match byte for byte. This is necessary for
# doing Range requests within a large video or PDF file, for example, or
# for compatibility with some CDNs that don't support weak ETags.
# * <tt>:last_modified</tt> Sets a "weak" last-update validator on the
# response. Subsequent requests that set If-Modified-Since may return a
# 304 Not Modified response if last_modified <= If-Modified-Since.
# * <tt>:public</tt> By default the Cache-Control header is private, set this to
# +true+ if you want your application to be cacheable by other devices (proxy caches).
# * <tt>:template</tt> By default, the template digest for the current
# controller/action is included in ETags. If the action renders a
# different template, you can include its digest instead. If the action
# doesn't render a template at all, you can pass <tt>template: false</tt>
# to skip any attempt to check for a template digest.
#
# === Example:
#
# def show
# @article = Article.find(params[:id])
#
# if stale?(etag: @article, last_modified: @article.updated_at)
# @statistics = @article.really_expensive_call
# respond_to do |format|
# # all the supported formats
# end
# end
# end
#
# You can also just pass a record. In this case +last_modified+ will be set
# by calling +updated_at+ and +etag+ by passing the object itself.
#
# def show
# @article = Article.find(params[:id])
#
# if stale?(@article)
# @statistics = @article.really_expensive_call
# respond_to do |format|
# # all the supported formats
# end
# end
# end
#
# You can also pass an object that responds to +maximum+, such as a
# collection of active records. In this case +last_modified+ will be set by
# calling +maximum(:updated_at)+ on the collection (the timestamp of the
# most recently updated record) and the +etag+ by passing the object itself.
#
# def index
# @articles = Article.all
#
# if stale?(@articles)
# @statistics = @articles.really_expensive_call
# respond_to do |format|
# # all the supported formats
# end
# end
# end
#
# When passing a record or a collection, you can still set the public header:
#
# def show
# @article = Article.find(params[:id])
#
# if stale?(@article, public: true)
# @statistics = @article.really_expensive_call
# respond_to do |format|
# # all the supported formats
# end
# end
# end
#
# When rendering a different template than the default controller/action
# style, you can indicate which digest to include in the ETag:
#
# def show
# super if stale? @article, template: 'widgets/show'
# end
#
def stale?(object = nil, **freshness_kwargs)
fresh_when(object, **freshness_kwargs)
!request.fresh?(response)
end
# Sets an HTTP 1.1 Cache-Control header. Defaults to issuing a +private+
# instruction, so that intermediate caches must not cache the response.
#
# expires_in 20.minutes
# expires_in 3.hours, public: true
# expires_in 3.hours, public: true, must_revalidate: true
#
# This method will overwrite an existing Cache-Control header.
# See https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities.
#
# HTTP Cache-Control Extensions for Stale Content. See https://tools.ietf.org/html/rfc5861
# It helps to cache an asset and serve it while is being revalidated and/or returning with an error.
#
# expires_in 3.hours, public: true, stale_while_revalidate: 60.seconds
# expires_in 3.hours, public: true, stale_while_revalidate: 60.seconds, stale_if_error: 5.minutes
#
# The method will also ensure an HTTP Date header for client compatibility.
def expires_in(seconds, options = {})
response.cache_control.merge!(
max_age: seconds,
public: options.delete(:public),
must_revalidate: options.delete(:must_revalidate),
stale_while_revalidate: options.delete(:stale_while_revalidate),
stale_if_error: options.delete(:stale_if_error),
)
options.delete(:private)
response.cache_control[:extras] = options.map { |k, v| "#{k}=#{v}" }
response.date = Time.now unless response.date?
end
# Sets an HTTP 1.1 Cache-Control header of <tt>no-cache</tt>. This means the
# resource will be marked as stale, so clients must always revalidate.
# Intermediate/browser caches may still store the asset.
def expires_now
response.cache_control.replace(no_cache: true)
end
# Cache or yield the block. The cache is supposed to never expire.
#
# You can use this method when you have an HTTP response that never changes,
# and the browser and proxies should cache it indefinitely.
#
# * +public+: By default, HTTP responses are private, cached only on the
# user's web browser. To allow proxies to cache the response, set +true+ to
# indicate that they can serve the cached response to all users.
def http_cache_forever(public: false)
expires_in 100.years, public: public
yield if stale?(etag: request.fullpath,
last_modified: Time.new(2011, 1, 1).utc,
public: public)
end
private
def combine_etags(validator, options)
[validator, *etaggers.map { |etagger| instance_exec(options, &etagger) }].compact
end
end
end
