Allow custom options for transferable headers and non-cached headers

lib/rack/cache/context.rb

@@ -237,7 +237,7 @@ def validate(entry)
 
  entry = entry.dup
  entry.headers.delete('date')
- %w[Date expires cache-control etag last-modified].each do |name|
+ %w[Date expires cache-control etag last-modified].concat(transfer_headers).each do |name|
  next unless value = response.headers[name]
  entry.headers[name] = value
  end
@@ -286,7 +286,7 @@ def fetch
  # Write the response to the cache.
  def store(response)
  strip_ignore_headers(response)
- metastore.store(@request, response, entitystore)
+ metastore.store(@request, response, entitystore, non_cached_headers)
  response.headers['age'] = response.age.to_s
  rescue => e
  log_error(e)

lib/rack/cache/meta_store.rb

@@ -58,7 +58,7 @@ def lookup(request, entity_store)
  # Write a cache entry to the store under the given key. Existing
  # entries are read and any that match the response are removed.
  # This method calls #write with the new list of cache entries.
- def store(request, response, entity_store)
+ def store(request, response, entity_store, non_cached_headers = [])
  key = cache_key(request)
  stored_env = persist_request(request)
 
@@ -97,6 +97,7 @@ def store(request, response, entity_store)
 
  headers = persist_response(response)
  headers.delete('age')
+ non_cached_headers.each{ |h| headers.delete(h) }
 
  entries.unshift [stored_env, headers]
  if request.env['rack-cache.use_native_ttl'] && response.fresh?

lib/rack/cache/options.rb

@@ -86,6 +86,19 @@ def option_name(key)
  # Default: ['set-cookie']
  option_accessor :ignore_headers
 
+ # Set of response headers that are transferred from the backend response
+ # onto the cache entry when validating a cached entity (after receiving a
+ # 304 response from the backend) before sending it to the client.
+ #
+ # Default: []
+ option_accessor :transfer_headers
+
+ # Set of response headers that will be passed to the client when present
+ # in any responses but will not be stored in cached entries.
+ #
+ # Default: []
+ option_accessor :non_cached_headers
+
  # Set of request headers that trigger "private" cache-control behavior
  # on responses that don't explicitly state whether the response is
  # public or private via a cache-control directive. Applications that use
@@ -142,18 +155,20 @@ def set(option, value=self, &block)
  private
  def initialize_options(options={})
  @default_options = {
- 'rack-cache.cache_key' => Key,
- 'rack-cache.verbose' => true,
- 'rack-cache.storage' => Rack::Cache::Storage.instance,
- 'rack-cache.metastore' => 'heap:/',
- 'rack-cache.entitystore' => 'heap:/',
- 'rack-cache.default_ttl' => 0,
- 'rack-cache.ignore_headers' => ['set-cookie'],
- 'rack-cache.private_headers' => ['Authorization', 'Cookie'],
- 'rack-cache.allow_reload' => false,
- 'rack-cache.allow_revalidate' => false,
- 'rack-cache.use_native_ttl' => false,
- 'rack-cache.fault_tolerant' => false,
+ 'rack-cache.cache_key' => Key,
+ 'rack-cache.verbose' => true,
+ 'rack-cache.storage' => Rack::Cache::Storage.instance,
+ 'rack-cache.metastore' => 'heap:/',
+ 'rack-cache.entitystore' => 'heap:/',
+ 'rack-cache.default_ttl' => 0,
+ 'rack-cache.ignore_headers' => ['set-cookie'],
+ 'rack-cache.transfer_headers' => [],
+ 'rack-cache.non_cached_headers' => [],
+ 'rack-cache.private_headers' => ['Authorization', 'Cookie'],
+ 'rack-cache.allow_reload' => false,
+ 'rack-cache.allow_revalidate' => false,
+ 'rack-cache.use_native_ttl' => false,
+ 'rack-cache.fault_tolerant' => false,
  }
  self.options = options
  end

test/context_test.rb

@@ -776,6 +776,58 @@
  cache.trace.wont_include :miss
  end
 
+ it 'includes specified additional headers from the backend in responses to the client' do
+ count = 0
+ respond_with do |req,res|
+ count += 1
+ res['ETAG'] = '"12345"'
+ res['unique-snowflake'] = '"so-special"'
+ res.status = (count == 1) ? 200 : 304
+ end
+
+ get '/', 'rack-cache.transfer_headers' => ['unique-snowflake']
+ assert app.called?
+ assert response.ok?
+ response.headers.must_include 'unique-snowflake'
+ response['unique-snowflake'].must_equal '"so-special"'
+ cache.trace.must_include :miss
+
+ get '/', 'rack-cache.transfer_headers' => ['unique-snowflake']
+ assert app.called?
+ assert response.ok?
+ response.headers.must_include 'unique-snowflake'
+ response['unique-snowflake'].must_equal '"so-special"'
+ cache.trace.must_include :valid
+ end
+
+ it 'excludes specified headers from being cached in responses' do
+ count = 0
+ respond_with do |req,res|
+ count += 1
+ res['ETAG'] = '"12345"'
+ if count == 1
+ res['not-cached'] = '"1"'
+ end
+ res.status = (count == 1) ? 200 : 304
+ end
+
+ get '/', 'rack-cache.non_cached_headers' => ['not-cached']
+ assert app.called?
+ assert response.ok?
+ response.headers.must_include 'not-cached'
+ cache.trace.must_include :miss
+ cache.trace.must_include :store
+ cache.trace.wont_include :ignore
+
+ get '/', 'rack-cache.non_cached_headers' => ['not-cached']
+ assert app.called?
+ assert response.ok?
+ response.headers.wont_include 'not-cached'
+ cache.trace.must_include :stale
+ cache.trace.must_include :valid
+ cache.trace.must_include :store
+ end
+
  it 'replaces cached responses when validation results in non-304 response' do
  timestamp = Time.now.httpdate
  count = 0