diff options
Diffstat (limited to 'actionpack/lib/action_dispatch/http/cache.rb')
| -rw-r--r-- | actionpack/lib/action_dispatch/http/cache.rb | 77 |
1 files changed, 55 insertions, 22 deletions
diff --git a/actionpack/lib/action_dispatch/http/cache.rb b/actionpack/lib/action_dispatch/http/cache.rb index 4bd727c14e..985e0fb972 100644 --- a/actionpack/lib/action_dispatch/http/cache.rb +++ b/actionpack/lib/action_dispatch/http/cache.rb @@ -2,9 +2,8 @@ module ActionDispatch module Http module Cache module Request - - HTTP_IF_MODIFIED_SINCE = 'HTTP_IF_MODIFIED_SINCE'.freeze - HTTP_IF_NONE_MATCH = 'HTTP_IF_NONE_MATCH'.freeze + HTTP_IF_MODIFIED_SINCE = "HTTP_IF_MODIFIED_SINCE".freeze + HTTP_IF_NONE_MATCH = "HTTP_IF_NONE_MATCH".freeze def if_modified_since if since = get_header(HTTP_IF_MODIFIED_SINCE) @@ -17,9 +16,7 @@ module ActionDispatch end def if_none_match_etags - (if_none_match ? if_none_match.split(/\s*,\s*/) : []).collect do |etag| - etag.gsub(/^\"|\"$/, "") - end + if_none_match ? if_none_match.split(/\s*,\s*/) : [] end def not_modified?(modified_at) @@ -28,8 +25,8 @@ module ActionDispatch def etag_matches?(etag) if etag - etag = etag.gsub(/^\"|\"$/, "") - if_none_match_etags.include?(etag) + validators = if_none_match_etags + validators.include?(etag) || validators.include?("*") end end @@ -80,30 +77,66 @@ module ActionDispatch set_header DATE, utc_time.httpdate end - # This method allows you to set the ETag for cached content, which - # will be returned to the end user. + # 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. # - # By default, Action Dispatch sets all ETags to be weak. - # This ensures that if the content changes only semantically, - # the whole page doesn't have to be regenerated from scratch - # by the web server. With strong ETags, pages are compared - # byte by byte, and are regenerated only if they are not exactly equal. - def etag=(etag) - key = ActiveSupport::Cache.expand_cache_key(etag) - super %(W/"#{Digest::MD5.hexdigest(key)}") + # Weak ETags are what we almost always need, so they're the default. + # Check out `#strong_etag=` to provide a strong ETag validator. + def etag=(weak_validators) + self.weak_etag = weak_validators + end + + def weak_etag=(weak_validators) + set_header "ETag", generate_weak_etag(weak_validators) + end + + def strong_etag=(strong_validators) + set_header "ETag", generate_strong_etag(strong_validators) end def etag?; etag; end + # True if an ETag is set and it's a weak validator (preceded with W/) + def weak_etag? + etag? && etag.starts_with?('W/"') + end + + # True if an ETag is set and it isn't a weak validator (not preceded with W/) + def strong_etag? + etag? && !weak_etag? + end + private - DATE = 'Date'.freeze + DATE = "Date".freeze LAST_MODIFIED = "Last-Modified".freeze SPECIAL_KEYS = Set.new(%w[extras no-cache max-age public private must-revalidate]) + def generate_weak_etag(validators) + "W/#{generate_strong_etag(validators)}" + end + + def generate_strong_etag(validators) + %("#{Digest::MD5.hexdigest(ActiveSupport::Cache.expand_cache_key(validators))}") + end + def cache_control_segments if cache_control = _cache_control - cache_control.delete(' ').split(',') + cache_control.delete(" ").split(",") else [] end @@ -113,10 +146,10 @@ module ActionDispatch cache_control = {} cache_control_segments.each do |segment| - directive, argument = segment.split('=', 2) + directive, argument = segment.split("=", 2) if SPECIAL_KEYS.include? directive - key = directive.tr('-', '_') + key = directive.tr("-", "_") cache_control[key.to_sym] = argument || true else cache_control[:extras] ||= [] |