parameters: (self, request)
return_statement: return False
docstring: Return a cached response if it exists in the cache, otherwise
          return False.
docstring_summary: Return a cached response if it exists in the cache, otherwise
          return False.
docstring_tokens: Return a cached response if it exists in the cache otherwise return False .
function: def cached_request(self, request):
          """
          Return a cached response if it exists in the cache, otherwise
          return False.
          """
          cache_url = self.cache_url(request.url)
          logger.debug('Looking up "%s" in the cache', cache_url)
          cc = self.parse_cache_control(request.headers)
  
          # Bail out if the request insists on fresh data
          if "no-cache" in cc:
              logger.debug('Request header has "no-cache", cache bypassed')
              return False
  
          if "max-age" in cc and cc["max-age"] == 0:
              logger.debug('Request header has "max_age" as 0, cache bypassed')
              return False
  
          # Request allows serving from the cache, let's see if we find something
          cache_data = self.cache.get(cache_url)
          if cache_data is None:
              logger.debug("No cache entry available")
              return False
  
          # Check whether it can be deserialized
          resp = self.serializer.loads(request, cache_data)
          if not resp:
              logger.warning("Cache entry deserialization failed, entry ignored")
              return False
  
          # If we have a cached 301, return it immediately. We don't
          # need to test our response for other headers b/c it is
          # intrinsically "cacheable" as it is Permanent.
          # See:
          #   https://tools.ietf.org/html/rfc7231#section-6.4.2
          #
          # Client can try to refresh the value by repeating the request
          # with cache busting headers as usual (ie no-cache).
          if resp.status == 301:
              msg = (
                  'Returning cached "301 Moved Permanently" response '
                  "(ignoring date and etag information)"
              )
              logger.debug(msg)
              return resp
  
          headers = CaseInsensitiveDict(resp.headers)
          if not headers or "date" not in headers:
              if "etag" not in headers:
                  # Without date or etag, the cached response can never be used
                  # and should be deleted.
                  logger.debug("Purging cached response: no date or etag")
                  self.cache.delete(cache_url)
              logger.debug("Ignoring cached response: no date")
              return False
  
          now = time.time()
          date = calendar.timegm(parsedate_tz(headers["date"]))
          current_age = max(0, now - date)
          logger.debug("Current age based on date: %i", current_age)
  
          # TODO: There is an assumption that the result will be a
          #       urllib3 response object. This may not be best since we
          #       could probably avoid instantiating or constructing the
          #       response until we know we need it.
          resp_cc = self.parse_cache_control(headers)
  
          # determine freshness
          freshness_lifetime = 0
  
          # Check the max-age pragma in the cache control header
          if "max-age" in resp_cc:
              freshness_lifetime = resp_cc["max-age"]
              logger.debug("Freshness lifetime from max-age: %i", freshness_lifetime)
  
          # If there isn't a max-age, check for an expires header
          elif "expires" in headers:
              expires = parsedate_tz(headers["expires"])
              if expires is not None:
                  expire_time = calendar.timegm(expires) - date
                  freshness_lifetime = max(0, expire_time)
                  logger.debug("Freshness lifetime from expires: %i", freshness_lifetime)
  
          # Determine if we are setting freshness limit in the
          # request. Note, this overrides what was in the response.
          if "max-age" in cc:
              freshness_lifetime = cc["max-age"]
              logger.debug(
                  "Freshness lifetime from request max-age: %i", freshness_lifetime
              )
  
          if "min-fresh" in cc:
              min_fresh = cc["min-fresh"]
              # adjust our current age by our min fresh
              current_age += min_fresh
              logger.debug("Adjusted current age from min-fresh: %i", current_age)
  
          # Return entry if it is fresh enough
          if freshness_lifetime > current_age:
              logger.debug('The response is "fresh", returning cached response')
              logger.debug("%i > %i", freshness_lifetime, current_age)
              return resp
  
          # we're not fresh. If we don't have an Etag, clear it out
          if "etag" not in headers:
              logger.debug('The cached response is "stale" with no etag, purging')
              self.cache.delete(cache_url)
  
          # return the original handler
          return False
function_tokens: def cached_request ( self , request ) : cache_url = self . cache_url ( request . url ) logger . debug ( 'Looking up "%s" in the cache' , cache_url ) cc = self . parse_cache_control ( request . headers ) # Bail out if the request insists on fresh data if "no-cache" in cc : logger . debug ( 'Request header has "no-cache", cache bypassed' ) return False if "max-age" in cc and cc [ "max-age" ] == 0 : logger . debug ( 'Request header has "max_age" as 0, cache bypassed' ) return False # Request allows serving from the cache, let's see if we find something cache_data = self . cache . get ( cache_url ) if cache_data is None : logger . debug ( "No cache entry available" ) return False # Check whether it can be deserialized resp = self . serializer . loads ( request , cache_data ) if not resp : logger . warning ( "Cache entry deserialization failed, entry ignored" ) return False # If we have a cached 301, return it immediately. We don't # need to test our response for other headers b/c it is # intrinsically "cacheable" as it is Permanent. # See: #   https://tools.ietf.org/html/rfc7231#section-6.4.2 # # Client can try to refresh the value by repeating the request # with cache busting headers as usual (ie no-cache). if resp . status == 301 : msg = ( 'Returning cached "301 Moved Permanently" response ' "(ignoring date and etag information)" ) logger . debug ( msg ) return resp headers = CaseInsensitiveDict ( resp . headers ) if not headers or "date" not in headers : if "etag" not in headers : # Without date or etag, the cached response can never be used # and should be deleted. logger . debug ( "Purging cached response: no date or etag" ) self . cache . delete ( cache_url ) logger . debug ( "Ignoring cached response: no date" ) return False now = time . time ( ) date = calendar . timegm ( parsedate_tz ( headers [ "date" ] ) ) current_age = max ( 0 , now - date ) logger . debug ( "Current age based on date: %i" , current_age ) # TODO: There is an assumption that the result will be a #       urllib3 response object. This may not be best since we #       could probably avoid instantiating or constructing the #       response until we know we need it. resp_cc = self . parse_cache_control ( headers ) # determine freshness freshness_lifetime = 0 # Check the max-age pragma in the cache control header if "max-age" in resp_cc : freshness_lifetime = resp_cc [ "max-age" ] logger . debug ( "Freshness lifetime from max-age: %i" , freshness_lifetime ) # If there isn't a max-age, check for an expires header elif "expires" in headers : expires = parsedate_tz ( headers [ "expires" ] ) if expires is not None : expire_time = calendar . timegm ( expires ) - date freshness_lifetime = max ( 0 , expire_time ) logger . debug ( "Freshness lifetime from expires: %i" , freshness_lifetime ) # Determine if we are setting freshness limit in the # request. Note, this overrides what was in the response. if "max-age" in cc : freshness_lifetime = cc [ "max-age" ] logger . debug ( "Freshness lifetime from request max-age: %i" , freshness_lifetime ) if "min-fresh" in cc : min_fresh = cc [ "min-fresh" ] # adjust our current age by our min fresh current_age += min_fresh logger . debug ( "Adjusted current age from min-fresh: %i" , current_age ) # Return entry if it is fresh enough if freshness_lifetime > current_age : logger . debug ( 'The response is "fresh", returning cached response' ) logger . debug ( "%i > %i" , freshness_lifetime , current_age ) return resp # we're not fresh. If we don't have an Etag, clear it out if "etag" not in headers : logger . debug ( 'The cached response is "stale" with no etag, purging' ) self . cache . delete ( cache_url ) # return the original handler return False