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Instance Public methods
expires_in(seconds, options = {}) Link
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 www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities.
HTTP Cache-Control Extensions for Stale Content. See 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
HTTP Cache-Control Extensions other values: developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control Any additional key-value pairs are concatenated onto the `Cache-Control` header in the response:
expires_in 3.hours, public: true, "s-maxage": 3.hours, "no-transform": true
The method will also ensure an HTTP Date
header for client compatibility.
# File actionpack/lib/action_controller/metal/conditional_get.rb, line 276 def expires_in(seconds, options = {}) response.cache_control.delete(:no_store) 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
expires_now() Link
Sets an HTTP 1.1 Cache-Control header of no-cache
. This means the resource will be marked as stale, so clients must always revalidate. Intermediate/browser caches may still store the asset.
fresh_when(object = nil, etag: nil, weak_etag: nil, strong_etag: nil, last_modified: nil, public: false, cache_control: {}, template: nil) Link
Sets the etag
, last_modified
, or both on the response and renders a 304 Not Modified
response if the request is already fresh.
Parameters:
-
:etag
Sets a “weak” ETag validator on the response. See the:weak_etag
option. -
:weak_etag
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 servingRange
requests within a PDF file. -
:strong_etag
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 doingRange
requests within a large video or PDF file, for example, or for compatibility with some CDNs that don't support weak ETags. -
:last_modified
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. -
:public
By default the Cache-Control header is private, set this totrue
if you want your application to be cacheable by other devices (proxy caches). -
:cache_control
When given will overwrite an existing Cache-Control header. See www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities. -
:template
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 passtemplate: false
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 304 Not Modified
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 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
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 overwriting Cache-Control header:
def show
@article = Article.find(params[:id])
fresh_when(@article, public: true, cache_control: { no_cache: true })
end
This will set in the response Cache-Control = public, no-cache.
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' }
# File actionpack/lib/action_controller/metal/conditional_get.rb, line 117 def fresh_when(object = nil, etag: nil, weak_etag: nil, strong_etag: nil, last_modified: nil, public: false, cache_control: {}, template: nil) response.cache_control.delete(:no_store) 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 response.cache_control.merge!(cache_control) head :not_modified if request.fresh?(response) end
http_cache_forever(public: false) Link
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, settrue
to indicate that they can serve the cached response to all users.
no_store() Link
Sets an HTTP 1.1 Cache-Control header of no-store
. This means the resource may not be stored in any cache.
stale?(object = nil, **freshness_kwargs) Link
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 304 Not Modified
is sent.
Parameters:
-
:etag
Sets a “weak” ETag validator on the response. See the:weak_etag
option. -
:weak_etag
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 servingRange
requests within a PDF file. -
:strong_etag
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 doingRange
requests within a large video or PDF file, for example, or for compatibility with some CDNs that don't support weak ETags. -
:last_modified
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. -
:public
By default the Cache-Control header is private, set this totrue
if you want your application to be cacheable by other devices (proxy caches). -
:cache_control
When given will overwrite an existing Cache-Control header. See www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities. -
:template
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 passtemplate: false
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 overwriting Cache-Control header:
def show
@article = Article.find(params[:id])
if stale?(@article, public: true, cache_control: { no_cache: true })
@statistics = @articles.really_expensive_call
respond_to do |format|
# all the supported formats
end
end
end
This will set in the response Cache-Control = public, no-cache.
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