class Rack::Cache::Response

Provides access to the response generated by the downstream application. The response, original_response, and entry objects exposed by the Core caching engine are instances of this class.

Response objects respond to a variety of convenience methods, including those defined in Rack::Response::Helpers, Rack::Cache::Headers, and Rack::Cache::ResponseHeaders.

Note that Rack::Cache::Response is not a subclass of Rack::Response and does not perform many of the same initialization and finalization tasks. For example, the body is not slurped during initialization and there are no facilities for generating response output.

Constants

CACHEABLE_RESPONSE_CODES

Status codes of responses that MAY be stored by a cache or used in reply to a subsequent request.

tools.ietf.org/html/rfc2616#section-13.4

NOT_MODIFIED_OMIT_HEADERS

Headers that MUST NOT be included with 304 Not Modified responses.

tools.ietf.org/html/rfc2616#section-10.3.5

Attributes

body[RW]

Rack response tuple accessors.

headers[RW]

Rack response tuple accessors.

now[R]

The time when the Response object was instantiated.

status[RW]

Rack response tuple accessors.

Public Class Methods

new(status, headers, body) click to toggle source

Create a Response instance given the response status code, header hash, and body.

   # File lib/rack/cache/response.rb
32 def initialize(status, headers, body)
33   @status = status.to_i
34   @headers = Rack::Utils::HeaderHash.new(headers)
35   @body = body
36   @now = Time.now
37   @headers['Date'] ||= @now.httpdate
38 end

Public Instance Methods

age() click to toggle source

The age of the response.

    # File lib/rack/cache/response.rb
148 def age
149   (headers['Age'] ||  [(now - date).to_i, 0].max).to_i
150 end
cache_control() click to toggle source

A Hash of name=value pairs that correspond to the Cache-Control header. Valueless parameters (e.g., must-revalidate, no-store) have a Hash value of true. This method always returns a Hash, empty if no Cache-Control header is present.

   # File lib/rack/cache/response.rb
68 def cache_control
69   @cache_control ||= CacheControl.new(headers['Cache-Control'])
70 end
cache_control=(value) click to toggle source

Set the Cache-Control header to the values specified by the Hash. See the cache_control method for information on expected Hash structure.

   # File lib/rack/cache/response.rb
74 def cache_control=(value)
75   if value.respond_to? :to_hash
76     cache_control.clear
77     cache_control.merge!(value)
78     value = cache_control.to_s
79   end
80 
81   if value.nil? || value.empty?
82     headers.delete('Cache-Control')
83   else
84     headers['Cache-Control'] = value
85   end
86 end
cacheable?() click to toggle source

Determine if the response is worth caching under any circumstance. Responses marked “private” with an explicit Cache-Control directive are considered uncacheable

Responses with neither a freshness lifetime (Expires, max-age) nor cache validator (Last-Modified, ETag) are considered uncacheable.

    # File lib/rack/cache/response.rb
102 def cacheable?
103   return false unless CACHEABLE_RESPONSE_CODES.include?(status)
104   return false if cache_control.no_store? || cache_control.private?
105   validateable? || fresh?
106 end
client_ttl=(seconds) click to toggle source

Set the response's time-to-live for private/client caches. This adjusts the Cache-Control/max-age directive.

    # File lib/rack/cache/response.rb
205 def client_ttl=(seconds)
206   self.max_age = age + seconds
207 end
date() click to toggle source

The date, as specified by the Date header. When no Date header is present, set the Date header to Time.now and return.

    # File lib/rack/cache/response.rb
138 def date
139   if date = headers['Date']
140     Time.httpdate(date)
141   else
142     headers['Date'] = now.httpdate unless headers.frozen?
143     now
144   end
145 end
etag() click to toggle source

The literal value of ETag HTTP header or nil if no ETag is specified.

    # File lib/rack/cache/response.rb
216 def etag
217   headers['ETag']
218 end
expire!() click to toggle source

Mark the response stale by setting the Age header to be equal to the maximum age of the response.

    # File lib/rack/cache/response.rb
132 def expire!
133   headers['Age'] = max_age.to_s if fresh?
134 end
expires() click to toggle source

The value of the Expires header as a Time object.

    # File lib/rack/cache/response.rb
165 def expires
166   headers['Expires'] && Time.httpdate(headers['Expires'])
167 rescue ArgumentError
168   nil
169 end
fresh?() click to toggle source

Determine if the response is “fresh”. Fresh responses may be served from cache without any interaction with the origin. A response is considered fresh when it includes a Cache-Control/max-age indicator or Expiration header and the calculated age is less than the freshness lifetime.

   # File lib/rack/cache/response.rb
92 def fresh?
93   ttl && ttl > 0
94 end
initialize_copy(other) click to toggle source
Calls superclass method
   # File lib/rack/cache/response.rb
40 def initialize_copy(other)
41   super
42   @headers = other.headers.dup
43 end
last_modified() click to toggle source

The String value of the Last-Modified header exactly as it appears in the response (i.e., no date parsing / conversion is performed).

    # File lib/rack/cache/response.rb
211 def last_modified
212   headers['Last-Modified']
213 end
max_age() click to toggle source

The number of seconds after the time specified in the response's Date header when the the response should no longer be considered fresh. First check for a r-maxage directive, then a s-maxage directive, then a max-age directive, and then fall back on an expires header; return nil when no maximum age can be established.

    # File lib/rack/cache/response.rb
157 def max_age
158   cache_control.reverse_max_age ||
159     cache_control.shared_max_age ||
160       cache_control.max_age ||
161        (expires && (expires - date))
162 end
max_age=(value) click to toggle source

The number of seconds after which the response should no longer be considered fresh. Sets the Cache-Control max-age directive.

    # File lib/rack/cache/response.rb
173 def max_age=(value)
174   self.cache_control = cache_control.merge('max-age' => value.to_s)
175 end
must_revalidate?() click to toggle source

Indicates that the cache must not serve a stale response in any circumstance without first revalidating with the origin. When present, the TTL of the response should not be overriden to be greater than the value provided by the origin.

    # File lib/rack/cache/response.rb
126 def must_revalidate?
127   cache_control.must_revalidate || cache_control.proxy_revalidate
128 end
not_modified!() click to toggle source

Modify the response so that it conforms to the rules defined for '304 Not Modified'. This sets the status, removes the body, and discards any headers that MUST NOT be included in 304 responses.

tools.ietf.org/html/rfc2616#section-10.3.5

    # File lib/rack/cache/response.rb
238 def not_modified!
239   body.close if body.respond_to?(:close)
240   self.status = 304
241   self.body = []
242   NOT_MODIFIED_OMIT_HEADERS.each { |name| headers.delete(name) }
243   nil
244 end
private=(value) click to toggle source

Mark the response “private”, making it ineligible for serving other clients.

    # File lib/rack/cache/response.rb
116 def private=(value)
117   value = value ? true : nil
118   self.cache_control = cache_control.
119     merge('public' => !value, 'private' => value)
120 end
reverse_max_age=(value) click to toggle source

Like shared_max_age= but sets the r-maxage directive, which applies only to reverse caches.

    # File lib/rack/cache/response.rb
185 def reverse_max_age=(value)
186   self.cache_control = cache_control.merge('r-maxage' => value.to_s)
187 end
shared_max_age=(value) click to toggle source

Like max_age= but sets the s-maxage directive, which applies only to shared caches.

    # File lib/rack/cache/response.rb
179 def shared_max_age=(value)
180   self.cache_control = cache_control.merge('s-maxage' => value.to_s)
181 end
to_a() click to toggle source

Return the status, headers, and body in a three-tuple.

   # File lib/rack/cache/response.rb
46 def to_a
47   [status, headers.to_hash, body]
48 end
ttl() click to toggle source

The response's time-to-live in seconds, or nil when no freshness information is present in the response. When the responses ttl is <= 0, the response may not be served from cache without first revalidating with the origin.

    # File lib/rack/cache/response.rb
193 def ttl
194   max_age - age if max_age
195 end
ttl=(seconds) click to toggle source

Set the response's time-to-live for shared caches to the specified number of seconds. This adjusts the Cache-Control/s-maxage directive.

    # File lib/rack/cache/response.rb
199 def ttl=(seconds)
200   self.shared_max_age = age + seconds
201 end
validateable?() click to toggle source

Determine if the response includes headers that can be used to validate the response with the origin using a conditional GET request.

    # File lib/rack/cache/response.rb
110 def validateable?
111   headers.key?('Last-Modified') || headers.key?('ETag')
112 end
vary() click to toggle source

The literal value of the Vary header, or nil when no header is present.

    # File lib/rack/cache/response.rb
247 def vary
248   headers['Vary']
249 end
vary?() click to toggle source

Does the response include a Vary header?

    # File lib/rack/cache/response.rb
252 def vary?
253   ! vary.nil?
254 end
vary_header_names() click to toggle source

An array of header names given in the Vary header or an empty array when no Vary header is present.

    # File lib/rack/cache/response.rb
258 def vary_header_names
259   return [] unless vary = headers['Vary']
260   vary.split(/[\s,]+/)
261 end