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Module: ActionDispatch::Http::Cache::Response

Constant Summary

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#cache_control (readonly)

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 54



attr_reader :cache_control


  








  

    #date   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 70



def date
  if date_header = get_header(DATE)
    Time.httpdate(date_header)
  end
end


  








  

    #date=(utc_time)   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 80



def date=(utc_time)
  set_header DATE, utc_time.httpdate
end


  








  

    #date?  ⇒ Boolean  (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 76



def date?
  has_header? DATE
end


  








  

    #etag=(weak_validators)   (rw)
  



  

    

This method sets a weak ETag validator on the response so browsers and proxies may cache the response, keyed on the ETag. On subsequent requests, the If-None-Match header is set to the cached ETag. If it matches the current ETag, we can return a 304 Not Modified response with no body, letting the browser or proxy know that their cache is current. Big savings in request time and network bandwidth.



Weak ETags are considered to be semantically equivalent but not byte-for-byte identical. This is perfect for browser caching of HTML pages where we don’t care about exact equality, just what the user is viewing.



Strong ETags are considered byte-for-byte identical. They allow a browser or proxy cache to support ::Range requests, useful for paging through a PDF file or scrubbing through a video. Some CDNs only support strong ETags and will ignore weak ETags entirely.



Weak ETags are what we almost always need, so they’re the default. Check out #strong_etag= to provide a strong ETag validator.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 102



def etag=(weak_validators)
  self.weak_etag = weak_validators
end


  








  

    #etag?  ⇒ Boolean  (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 114



def etag?; etag; end


  








  

    #last_modified   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 56



def last_modified
  if last = get_header(LAST_MODIFIED)
    Time.httpdate(last)
  end
end


  








  

    #last_modified=(utc_time)   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 66



def last_modified=(utc_time)
  set_header LAST_MODIFIED, utc_time.httpdate
end


  








  

    #last_modified?  ⇒ Boolean  (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 62



def last_modified?
  has_header? LAST_MODIFIED
end


  








  

    #strong_etag=(strong_validators)   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 110



def strong_etag=(strong_validators)
  set_header "ETag", generate_strong_etag(strong_validators)
end


  








  

    #strong_etag?  ⇒ Boolean  (rw)
  



  

    

True if an ETag is set, and it isn’t a weak validator (not preceded with W/).


  





  


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 123



def strong_etag?
  etag? && !weak_etag?
end


  








  

    #weak_etag=(weak_validators)   (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 106



def weak_etag=(weak_validators)
  set_header "ETag", generate_weak_etag(weak_validators)
end


  








  

    #weak_etag?  ⇒ Boolean  (rw)
  



  

    

True if an ETag is set, and it’s a weak validator (preceded with W/).


  





  


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 117



def weak_etag?
  etag? && etag.start_with?('W/"')
end


  







Instance Method Details



  

    #cache_control_headers   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 146



def cache_control_headers
  cache_control = {}

  cache_control_segments&.each do |segment|
    directive, argument = segment.split("=", 2)

    if SPECIAL_KEYS.include? directive
      directive.tr!("-", "_")
      cache_control[directive.to_sym] = argument || true
    else
      cache_control[:extras] ||= []
      cache_control[:extras] << segment
    end
  end

  cache_control
end


  








  

    #cache_control_segments   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 140



def cache_control_segments
  if cache_control = _cache_control
    cache_control.delete(" ").split(",")
  end
end


  








  

    #generate_strong_etag(validators)   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 136



def generate_strong_etag(validators)
  %("#{ActiveSupport::Digest.hexdigest(ActiveSupport::Cache.expand_cache_key(validators))}")
end


  








  

    #generate_weak_etag(validators)   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 132



def generate_weak_etag(validators)
  "W/#{generate_strong_etag(validators)}"
end


  








  

    #handle_conditional_get!   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 175



def handle_conditional_get!
  # Normally default cache control setting is handled by ETag middleware. But, if
  # an etag is already set, the middleware defaults to `no-cache` unless a default
  # `Cache-Control` value is previously set. So, set a default one here.
  if (etag? || last_modified?) && !self._cache_control
    self._cache_control = DEFAULT_CACHE_CONTROL
  end
end


  








  

    #merge_and_normalize_cache_control!(cache_control)   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 184



def merge_and_normalize_cache_control!(cache_control)
  control = cache_control_headers

  return if control.empty? && cache_control.empty?  # Let middleware handle default behavior

  if cache_control.any?
    # Any caching directive coming from a controller overrides no-cache/no-store in
    # the default Cache-Control header.
    control.delete(:no_cache)
    control.delete(:no_store)

    if extras = control.delete(:extras)
      cache_control[:extras] ||= []
      cache_control[:extras] += extras
      cache_control[:extras].uniq!
    end

    control.merge! cache_control
  end

  options = []

  if control[:no_store]
    options << PRIVATE if control[:private]
    options << NO_STORE
  elsif control[:no_cache]
    options << PUBLIC if control[:public]
    options << NO_CACHE
    options.concat(control[:extras]) if control[:extras]
  else
    extras = control[:extras]
    max_age = control[:max_age]
    stale_while_revalidate = control[:stale_while_revalidate]
    stale_if_error = control[:stale_if_error]

    options << "max-age=#{max_age.to_i}" if max_age
    options << (control[:public] ? PUBLIC : PRIVATE)
    options << MUST_REVALIDATE if control[:must_revalidate]
    options << "stale-while-revalidate=#{stale_while_revalidate.to_i}" if stale_while_revalidate
    options << "stale-if-error=#{stale_if_error.to_i}" if stale_if_error
    options.concat(extras) if extras
  end

  self._cache_control = options.join(", ")
end


  








  

    #prepare_cache_control!   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 164



def prepare_cache_control!
  @cache_control = cache_control_headers
end