cache.rb in activesupport-4.0.0.beta1

- old
+ new

@@ -1,11 +1,10 @@
 require 'benchmark'
 require 'zlib'
 require 'active_support/core_ext/array/extract_options'
 require 'active_support/core_ext/array/wrap'
 require 'active_support/core_ext/benchmark'
-require 'active_support/core_ext/exception'
 require 'active_support/core_ext/class/attribute_accessors'
 require 'active_support/core_ext/numeric/bytes'
 require 'active_support/core_ext/numeric/time'
 require 'active_support/core_ext/object/to_param'
 require 'active_support/core_ext/string/inflections'
@@ -43,12 +42,12 @@
       #   # => returns a new ActiveSupport::Cache::MemCacheStore object
       #
       # Any additional arguments will be passed to the corresponding cache store
       # class's constructor:
       #
-      #   ActiveSupport::Cache.lookup_store(:file_store, "/tmp/cache")
-      #   # => same as: ActiveSupport::Cache::FileStore.new("/tmp/cache")
+      #   ActiveSupport::Cache.lookup_store(:file_store, '/tmp/cache')
+      #   # => same as: ActiveSupport::Cache::FileStore.new('/tmp/cache')
       #
       # If the first argument is not a Symbol, then it will simply be returned:
       #
       #   ActiveSupport::Cache.lookup_store(MyOwnCacheStore.new)
       #   # => returns MyOwnCacheStore.new
@@ -89,10 +88,11 @@
 
       def retrieve_cache_key(key)
         case
         when key.respond_to?(:cache_key) then key.cache_key
         when key.is_a?(Array)            then key.map { |element| retrieve_cache_key(element) }.to_param
+        when key.respond_to?(:to_a)      then retrieve_cache_key(key.to_a)
         else                                  key.to_param
         end.to_s
       end
     end
 
@@ -107,50 +107,50 @@
     #
     # ActiveSupport::Cache::Store can store any serializable Ruby object.
     #
     #   cache = ActiveSupport::Cache::MemoryStore.new
     #
-    #   cache.read("city")   # => nil
-    #   cache.write("city", "Duckburgh")
-    #   cache.read("city")   # => "Duckburgh"
+    #   cache.read('city')   # => nil
+    #   cache.write('city', "Duckburgh")
+    #   cache.read('city')   # => "Duckburgh"
     #
     # Keys are always translated into Strings and are case sensitive. When an
     # object is specified as a key and has a +cache_key+ method defined, this
     # method will be called to define the key.  Otherwise, the +to_param+
     # method will be called. Hashes and Arrays can also be used as keys. The
     # elements will be delimited by slashes, and the elements within a Hash
     # will be sorted by key so they are consistent.
     #
-    #   cache.read("city") == cache.read(:city)   # => true
+    #   cache.read('city') == cache.read(:city)   # => true
     #
     # Nil values can be cached.
     #
     # If your cache is on a shared infrastructure, you can define a namespace
     # for your cache entries. If a namespace is defined, it will be prefixed on
     # to every key. The namespace can be either a static value or a Proc. If it
     # is a Proc, it will be invoked when each key is evaluated so that you can
     # use application logic to invalidate keys.
     #
-    #   cache.namespace = lambda { @last_mod_time }  # Set the namespace to a variable
+    #   cache.namespace = -> { @last_mod_time }  # Set the namespace to a variable
     #   @last_mod_time = Time.now  # Invalidate the entire cache by changing namespace
     #
-    #
     # Caches can also store values in a compressed format to save space and
     # reduce time spent sending data. Since there is overhead, values must be
     # large enough to warrant compression. To turn on compression either pass
-    # <tt>:compress => true</tt> in the initializer or as an option to +fetch+
+    # <tt>compress: true</tt> in the initializer or as an option to +fetch+
     # or +write+. To specify the threshold at which to compress values, set the
     # <tt>:compress_threshold</tt> option. The default threshold is 16K.
     class Store
 
       cattr_accessor :logger, :instance_writer => true
 
       attr_reader :silence, :options
       alias :silence? :silence
 
-      # Create a new cache. The options will be passed to any write method calls except
-      # for :namespace which can be used to set the global namespace for the cache.
+      # Create a new cache. The options will be passed to any write method calls
+      # except for <tt>:namespace</tt> which can be used to set the global
+      # namespace for the cache.
       def initialize(options = nil)
         @options = options ? options.dup : {}
       end
 
       # Silence the logger.
@@ -165,11 +165,12 @@
         yield
       ensure
         @silence = previous_silence
       end
 
-      # Set to true if cache stores should be instrumented. Default is false.
+      # Set to +true+ if cache stores should be instrumented.
+      # Default is +false+.
       def self.instrument=(boolean)
         Thread.current[:instrument_cache_store] = boolean
       end
 
       def self.instrument
@@ -177,138 +178,122 @@
       end
 
       # Fetches data from the cache, using the given key. If there is data in
       # the cache with the given key, then that data is returned.
       #
-      # If there is no such data in the cache (a cache miss), then nil will be
-      # returned. However, if a block has been passed, that block will be run
-      # in the event of a cache miss. The return value of the block will be
-      # written to the cache under the given cache key, and that return value
-      # will be returned.
+      # If there is no such data in the cache (a cache miss), then +nil+ will be
+      # returned. However, if a block has been passed, that block will be passed
+      # the key and executed in the event of a cache miss. The return value of the
+      # block will be written to the cache under the given cache key, and that
+      # return value will be returned.
       #
-      #   cache.write("today", "Monday")
-      #   cache.fetch("today")  # => "Monday"
+      #   cache.write('today', 'Monday')
+      #   cache.fetch('today')  # => "Monday"
       #
-      #   cache.fetch("city")   # => nil
-      #   cache.fetch("city") do
-      #     "Duckburgh"
+      #   cache.fetch('city')   # => nil
+      #   cache.fetch('city') do
+      #     'Duckburgh'
       #   end
-      #   cache.fetch("city")   # => "Duckburgh"
+      #   cache.fetch('city')   # => "Duckburgh"
       #
       # You may also specify additional options via the +options+ argument.
-      # Setting <tt>:force => true</tt> will force a cache miss:
+      # Setting <tt>force: true</tt> will force a cache miss:
       #
-      #   cache.write("today", "Monday")
-      #   cache.fetch("today", :force => true)  # => nil
+      #   cache.write('today', 'Monday')
+      #   cache.fetch('today', force: true)  # => nil
       #
       # Setting <tt>:compress</tt> will store a large cache entry set by the call
       # in a compressed format.
       #
-      #
       # Setting <tt>:expires_in</tt> will set an expiration time on the cache.
       # All caches support auto-expiring content after a specified number of
       # seconds. This value can be specified as an option to the constructor
       # (in which case all entries will be affected), or it can be supplied to
       # the +fetch+ or +write+ method to effect just one entry.
       #
-      #   cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 5.minutes)
-      #   cache.write(key, value, :expires_in => 1.minute)  # Set a lower value for one entry
+      #   cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 5.minutes)
+      #   cache.write(key, value, expires_in: 1.minute) # Set a lower value for one entry
       #
-      # Setting <tt>:race_condition_ttl</tt> is very useful in situations where a cache entry
-      # is used very frequently and is under heavy load. If a cache expires and due to heavy load
-      # seven different processes will try to read data natively and then they all will try to
-      # write to cache. To avoid that case the first process to find an expired cache entry will
-      # bump the cache expiration time by the value set in <tt>:race_condition_ttl</tt>. Yes
-      # this process is extending the time for a stale value by another few seconds. Because
-      # of extended life of the previous cache, other processes will continue to use slightly
-      # stale data for a just a big longer. In the meantime that first process will go ahead
-      # and will write into cache the new value. After that all the processes will start
-      # getting new value. The key is to keep <tt>:race_condition_ttl</tt> small.
+      # Setting <tt>:race_condition_ttl</tt> is very useful in situations where
+      # a cache entry is used very frequently and is under heavy load. If a
+      # cache expires and due to heavy load seven different processes will try
+      # to read data natively and then they all will try to write to cache. To
+      # avoid that case the first process to find an expired cache entry will
+      # bump the cache expiration time by the value set in <tt>:race_condition_ttl</tt>.
+      # Yes, this process is extending the time for a stale value by another few
+      # seconds. Because of extended life of the previous cache, other processes
+      # will continue to use slightly stale data for a just a big longer. In the
+      # meantime that first process will go ahead and will write into cache the
+      # new value. After that all the processes will start getting new value.
+      # The key is to keep <tt>:race_condition_ttl</tt> small.
       #
-      # If the process regenerating the entry errors out, the entry will be regenerated
-      # after the specified number of seconds. Also note that the life of stale cache is
-      # extended only if it expired recently. Otherwise a new value is generated and
-      # <tt>:race_condition_ttl</tt> does not play any role.
+      # If the process regenerating the entry errors out, the entry will be
+      # regenerated after the specified number of seconds. Also note that the
+      # life of stale cache is extended only if it expired recently. Otherwise
+      # a new value is generated and <tt>:race_condition_ttl</tt> does not play
+      # any role.
       #
       #   # Set all values to expire after one minute.
-      #   cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 1.minute)
+      #   cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 1.minute)
       #
-      #   cache.write("foo", "original value")
+      #   cache.write('foo', 'original value')
       #   val_1 = nil
       #   val_2 = nil
       #   sleep 60
       #
       #   Thread.new do
-      #     val_1 = cache.fetch("foo", :race_condition_ttl => 10) do
+      #     val_1 = cache.fetch('foo', race_condition_ttl: 10) do
       #       sleep 1
-      #       "new value 1"
+      #       'new value 1'
       #     end
       #   end
       #
       #   Thread.new do
-      #     val_2 = cache.fetch("foo", :race_condition_ttl => 10) do
-      #       "new value 2"
+      #     val_2 = cache.fetch('foo', race_condition_ttl: 10) do
+      #       'new value 2'
       #     end
       #   end
       #
       #   # val_1 => "new value 1"
       #   # val_2 => "original value"
       #   # sleep 10 # First thread extend the life of cache by another 10 seconds
-      #   # cache.fetch("foo") => "new value 1"
+      #   # cache.fetch('foo') => "new value 1"
       #
       # Other options will be handled by the specific cache store implementation.
-      # Internally, #fetch calls #read_entry, and calls #write_entry on a cache miss.
-      # +options+ will be passed to the #read and #write calls.
+      # Internally, #fetch calls #read_entry, and calls #write_entry on a cache
+      # miss. +options+ will be passed to the #read and #write calls.
       #
       # For example, MemCacheStore's #write method supports the +:raw+
       # option, which tells the memcached server to store all values as strings.
       # We can use this option with #fetch too:
       #
       #   cache = ActiveSupport::Cache::MemCacheStore.new
-      #   cache.fetch("foo", :force => true, :raw => true) do
+      #   cache.fetch("foo", force: true, raw: true) do
       #     :bar
       #   end
-      #   cache.fetch("foo")  # => "bar"
+      #   cache.fetch('foo') # => "bar"
       def fetch(name, options = nil)
         if block_given?
           options = merged_options(options)
           key = namespaced_key(name, options)
-          unless options[:force]
-            entry = instrument(:read, name, options) do |payload|
-              payload[:super_operation] = :fetch if payload
-              read_entry(key, options)
-            end
-          end
-          if entry && entry.expired?
-            race_ttl = options[:race_condition_ttl].to_f
-            if race_ttl and Time.now.to_f - entry.expires_at <= race_ttl
-              entry.expires_at = Time.now + race_ttl
-              write_entry(key, entry, :expires_in => race_ttl * 2)
-            else
-              delete_entry(key, options)
-            end
-            entry = nil
-          end
 
+          cached_entry = find_cached_entry(key, name, options) unless options[:force]
+          entry = handle_expired_entry(cached_entry, key, options)
+
           if entry
-            instrument(:fetch_hit, name, options) { |payload| }
-            entry.value
+            get_entry_value(entry, name, options)
           else
-            result = instrument(:generate, name, options) do |payload|
-              yield
-            end
-            write(name, result, options)
-            result
+            save_block_result_to_cache(name, options) { |_name| yield _name }
           end
         else
           read(name, options)
         end
       end
 
       # Fetches data from the cache, using the given key. If there is data in
       # the cache with the given key, then that data is returned. Otherwise,
-      # nil is returned.
+      # +nil+ is returned.
       #
       # Options are passed to the underlying cache implementation.
       def read(name, options = nil)
         options = merged_options(options)
         key = namespaced_key(name, options)
@@ -373,22 +358,18 @@
         instrument(:delete, name) do |payload|
           delete_entry(namespaced_key(name, options), options)
         end
       end
 
-      # Return true if the cache contains an entry for the given key.
+      # Return +true+ if the cache contains an entry for the given key.
       #
       # Options are passed to the underlying cache implementation.
       def exist?(name, options = nil)
         options = merged_options(options)
         instrument(:exist?, name) do |payload|
           entry = read_entry(namespaced_key(name, options), options)
-          if entry && !entry.expired?
-            true
-          else
-            false
-          end
+          entry && !entry.expired?
         end
       end
 
       # Delete all entries with keys matching the pattern.
       #
@@ -406,11 +387,11 @@
       # All implementations may not support this method.
       def increment(name, amount = 1, options = nil)
         raise NotImplementedError.new("#{self.class.name} does not support increment")
       end
 
-      # Increment an integer value in the cache.
+      # Decrement an integer value in the cache.
       #
       # Options are passed to the underlying cache implementation.
       #
       # All implementations may not support this method.
       def decrement(name, amount = 1, options = nil)
@@ -435,13 +416,14 @@
       def clear(options = nil)
         raise NotImplementedError.new("#{self.class.name} does not support clear")
       end
 
       protected
-        # Add the namespace defined in the options to a pattern designed to match keys.
-        # Implementations that support delete_matched should call this method to translate
-        # a pattern that matches names into one that matches namespaced keys.
+        # Add the namespace defined in the options to a pattern designed to
+        # match keys. Implementations that support delete_matched should call
+        # this method to translate a pattern that matches names into one that
+        # matches namespaced keys.
         def key_matcher(pattern, options)
           prefix = options[:namespace].is_a?(Proc) ? options[:namespace].call : options[:namespace]
           if prefix
             source = pattern.source
             if source.start_with?('^')
@@ -453,21 +435,24 @@
           else
             pattern
           end
         end
 
-        # Read an entry from the cache implementation. Subclasses must implement this method.
+        # Read an entry from the cache implementation. Subclasses must implement
+        # this method.
         def read_entry(key, options) # :nodoc:
           raise NotImplementedError.new
         end
 
-        # Write an entry to the cache implementation. Subclasses must implement this method.
+        # Write an entry to the cache implementation. Subclasses must implement
+        # this method.
         def write_entry(key, entry, options) # :nodoc:
           raise NotImplementedError.new
         end
 
-        # Delete an entry from the cache implementation. Subclasses must implement this method.
+        # Delete an entry from the cache implementation. Subclasses must
+        # implement this method.
         def delete_entry(key, options) # :nodoc:
           raise NotImplementedError.new
         end
 
       private
@@ -479,11 +464,11 @@
             options.dup
           end
         end
 
         # Expand key to be a consistent string value. Invoke +cache_key+ if
-        # object responds to +cache_key+. Otherwise, to_param method will be
+        # object responds to +cache_key+. Otherwise, +to_param+ method will be
         # called. If the key is a Hash, then keys will be sorted alphabetically.
         def expanded_key(key) # :nodoc:
           return key.cache_key.to_s if key.respond_to?(:cache_key)
 
           case key
@@ -498,11 +483,12 @@
           end
 
           key.to_param
         end
 
-        # Prefix a key with the namespace. Namespace and key will be delimited with a colon.
+        # Prefix a key with the namespace. Namespace and key will be delimited
+        # with a colon.
         def namespaced_key(key, options)
           key = expanded_key(key)
           namespace = options[:namespace] if options
           prefix = namespace.is_a?(Proc) ? namespace.call : namespace
           key = "#{prefix}:#{key}" if prefix
@@ -523,116 +509,162 @@
 
         def log(operation, key, options = nil)
           return unless logger && logger.debug? && !silence?
           logger.debug("Cache #{operation}: #{key}#{options.blank? ? "" : " (#{options.inspect})"}")
         end
-    end
 
-    # Entry that is put into caches. It supports expiration time on entries and can compress values
-    # to save space in the cache.
-    class Entry
-      attr_reader :created_at, :expires_in
+        def find_cached_entry(key, name, options)
+          instrument(:read, name, options) do |payload|
+            payload[:super_operation] = :fetch if payload
+            read_entry(key, options)
+          end
+        end
 
-      DEFAULT_COMPRESS_LIMIT = 16.kilobytes
-
-      class << self
-        # Create an entry with internal attributes set. This method is intended to be
-        # used by implementations that store cache entries in a native format instead
-        # of as serialized Ruby objects.
-        def create(raw_value, created_at, options = {})
-          entry = new(nil)
-          entry.instance_variable_set(:@value, raw_value)
-          entry.instance_variable_set(:@created_at, created_at.to_f)
-          entry.instance_variable_set(:@compressed, options[:compressed])
-          entry.instance_variable_set(:@expires_in, options[:expires_in])
+        def handle_expired_entry(entry, key, options)
+          if entry && entry.expired?
+            race_ttl = options[:race_condition_ttl].to_i
+            if race_ttl && (Time.now - entry.expires_at <= race_ttl)
+              # When an entry has :race_condition_ttl defined, put the stale entry back into the cache
+              # for a brief period while the entry is begin recalculated.
+              entry.expires_at = Time.now + race_ttl
+              write_entry(key, entry, :expires_in => race_ttl * 2)
+            else
+              delete_entry(key, options)
+            end
+            entry = nil
+          end
           entry
         end
-      end
 
+        def get_entry_value(entry, name, options)
+          instrument(:fetch_hit, name, options) { |payload| }
+          entry.value
+        end
+
+        def save_block_result_to_cache(name, options)
+          result = instrument(:generate, name, options) do |payload|
+            yield(name)
+          end
+          write(name, result, options)
+          result
+        end
+    end
+
+    # This class is used to represent cache entries. Cache entries have a value and an optional
+    # expiration time. The expiration time is used to support the :race_condition_ttl option
+    # on the cache.
+    #
+    # Since cache entries in most instances will be serialized, the internals of this class are highly optimized
+    # using short instance variable names that are lazily defined.
+    class Entry # :nodoc:
+      DEFAULT_COMPRESS_LIMIT = 16.kilobytes
+
       # Create a new cache entry for the specified value. Options supported are
       # +:compress+, +:compress_threshold+, and +:expires_in+.
       def initialize(value, options = {})
-        @compressed = false
-        @expires_in = options[:expires_in]
-        @expires_in = @expires_in.to_f if @expires_in
-        @created_at = Time.now.to_f
-        if value.nil?
-          @value = nil
+        if should_compress?(value, options)
+          @v = compress(value)
+          @c = true
         else
-          @value = Marshal.dump(value)
-          if should_compress?(@value, options)
-            @value = Zlib::Deflate.deflate(@value)
-            @compressed = true
-          end
+          @v = value
         end
+        if expires_in = options[:expires_in]
+          @x = (Time.now + expires_in).to_i
+        end
       end
 
-      # Get the raw value. This value may be serialized and compressed.
-      def raw_value
-        @value
-      end
-
-      # Get the value stored in the cache.
       def value
-        # If the original value was exactly false @value is still true because
-        # it is marshalled and eventually compressed. Both operations yield
-        # strings.
-        if @value
-          # In rails 3.1 and earlier values in entries did not marshaled without
-          # options[:compress] and if it's Numeric.
-          # But after commit a263f377978fc07515b42808ebc1f7894fafaa3a
-          # all values in entries are marshalled. And after that code below expects
-          # that all values in entries will be marshaled (and will be strings). 
-          # So here we need a check for old ones.
-          begin
-            Marshal.load(compressed? ? Zlib::Inflate.inflate(@value) : @value)
-          rescue TypeError
-            compressed? ? Zlib::Inflate.inflate(@value) : @value
-          end
-        end
+        convert_version_3_entry! if defined?(@value)
+        compressed? ? uncompress(@v) : @v
       end
 
-      def compressed?
-        @compressed
-      end
-
-      # Check if the entry is expired. The +expires_in+ parameter can override the
-      # value set when the entry was created.
+      # Check if the entry is expired. The +expires_in+ parameter can override
+      # the value set when the entry was created.
       def expired?
-        @expires_in && @created_at + @expires_in <= Time.now.to_f
-      end
-
-      # Set a new time when the entry will expire.
-      def expires_at=(time)
-        if time
-          @expires_in = time.to_f - @created_at
+        convert_version_3_entry! if defined?(@value)
+        if defined?(@x)
+          @x && @x < Time.now.to_i
         else
-          @expires_in = nil
+          false
         end
       end
 
-      # Seconds since the epoch when the entry will expire.
       def expires_at
-        @expires_in ? @created_at + @expires_in : nil
+        Time.at(@x) if defined?(@x)
       end
 
-      # Returns the size of the cached value. This could be less than value.size
-      # if the data is compressed.
+      def expires_at=(value)
+        @x = value.to_i
+      end
+
+      # Returns the size of the cached value. This could be less than
+      # <tt>value.size</tt> if the data is compressed.
       def size
-        if @value.nil?
-          0
+        if defined?(@s)
+          @s
         else
-          @value.bytesize
+          case value
+          when NilClass
+            0
+          when String
+            @v.bytesize
+          else
+            @s = Marshal.dump(@v).bytesize
+          end
         end
       end
 
+      # Duplicate the value in a class. This is used by cache implementations that don't natively
+      # serialize entries to protect against accidental cache modifications.
+      def dup_value!
+        convert_version_3_entry! if defined?(@value)
+        if @v && !compressed? && !(@v.is_a?(Numeric) || @v == true || @v == false)
+          if @v.is_a?(String)
+            @v = @v.dup
+          else
+            @v = Marshal.load(Marshal.dump(@v))
+          end
+        end
+      end
+
       private
-        def should_compress?(serialized_value, options)
-          if options[:compress]
+        def should_compress?(value, options)
+          if value && options[:compress]
             compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT
-            return true if serialized_value.size >= compress_threshold
+            serialized_value_size = (value.is_a?(String) ? value : Marshal.dump(value)).bytesize
+            return true if serialized_value_size >= compress_threshold
           end
           false
+        end
+
+        def compressed?
+          defined?(@c) ? @c : false
+        end
+
+        def compress(value)
+          Zlib::Deflate.deflate(Marshal.dump(value))
+        end
+
+        def uncompress(value)
+          Marshal.load(Zlib::Inflate.inflate(value))
+        end
+
+        # The internals of this method changed between Rails 3.x and 4.0. This method provides the glue
+        # to ensure that cache entries created under the old version still work with the new class definition.
+        def convert_version_3_entry!
+          if defined?(@value)
+            @v = @value
+            remove_instance_variable(:@value)
+          end
+          if defined?(@compressed)
+            @c = @compressed
+            remove_instance_variable(:@compressed)
+          end
+          if defined?(@expires_in) && defined?(@created_at) && @expires_in && @created_at
+            @x = (@created_at + @expires_in).to_i
+            remove_instance_variable(:@created_at)
+            remove_instance_variable(:@expires_in)
+          end
         end
     end
   end
 end