lib/active_support/cache.rb in activesupport-3.0.0.beta3 vs lib/active_support/cache.rb in activesupport-3.0.0.beta4
- old
+ new
@@ -1,22 +1,32 @@
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'
module ActiveSupport
# See ActiveSupport::Cache::Store for documentation.
module Cache
autoload :FileStore, 'active_support/cache/file_store'
autoload :MemoryStore, 'active_support/cache/memory_store'
- autoload :SynchronizedMemoryStore, 'active_support/cache/synchronized_memory_store'
autoload :MemCacheStore, 'active_support/cache/mem_cache_store'
+ autoload :SynchronizedMemoryStore, 'active_support/cache/synchronized_memory_store'
autoload :CompressedMemCacheStore, 'active_support/cache/compressed_mem_cache_store'
+ EMPTY_OPTIONS = {}.freeze
+
+ # These options mean something to all cache implementations. Individual cache
+ # implementations may support additional optons.
+ UNIVERSAL_OPTIONS = [:namespace, :compress, :compress_threshold, :expires_in, :race_condition_ttl]
+
module Strategy
autoload :LocalCache, 'active_support/cache/strategy/local_cache'
end
# Creates a new CacheStore object according to the given options.
@@ -57,19 +67,16 @@
else
store
end
end
- RAILS_CACHE_ID = ENV["RAILS_CACHE_ID"]
- RAILS_APP_VERION = ENV["RAILS_APP_VERION"]
- EXPANDED_CACHE = RAILS_CACHE_ID || RAILS_APP_VERION
-
def self.expand_cache_key(key, namespace = nil)
expanded_cache_key = namespace ? "#{namespace}/" : ""
- if EXPANDED_CACHE
- expanded_cache_key << "#{RAILS_CACHE_ID || RAILS_APP_VERION}/"
+ prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]
+ if prefix
+ expanded_cache_key << "#{prefix}/"
end
expanded_cache_key <<
if key.respond_to?(:cache_key)
key.cache_key
@@ -90,30 +97,79 @@
# implementations, each having its own additional features. See the classes
# under the ActiveSupport::Cache module, e.g.
# ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most
# popular cache store for large production websites.
#
- # ActiveSupport::Cache::Store is meant for caching strings. Some cache
- # store implementations, like MemoryStore, are able to cache arbitrary
- # Ruby objects, but don't count on every cache store to be able to do that.
+ # Some implementations may not support all methods beyond the basic cache
+ # methods of +fetch+, +write+, +read+, +exist?+, and +delete+.
#
+ # 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"
+ #
+ # Keys are always translated into Strings and are case sensitive. When an
+ # object is specified as a key, its +cache_key+ method will be called if it
+ # is defined. Otherwise, the +to_param+ method will be called. Hashes and
+ # Arrays can be used as keys. The elements will be delimited by slashes
+ # and Hashes elements will be sorted by key so they are consistent.
+ #
+ # 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
+ # @last_mod_time = Time.now # Invalidate the entire cache by changing namespace
+ #
+ # All caches support auto expiring content after a specified number of seconds.
+ # To set the cache entry time to live, you can either specify +:expires_in+ as
+ # an option to the constructor to have it affect all entries or to the +fetch+
+ # or +write+ methods for just one entry.
+ #
+ # cache = ActiveSupport::Cache::MemoryStore.new(:expire_in => 5.minutes)
+ # cache.write(key, value, :expire_in => 1.minute) # Set a lower value for one entry
+ #
+ # Caches can also store values in a compressed format to save space and reduce
+ # time spent sending data. Since there is some overhead, values must be large
+ # enough to warrant compression. To turn on compression either pass
+ # <tt>:compress => true</tt> in the initializer or to +fetch+ or +write+.
+ # To specify the threshold at which to compress values, set
+ # <tt>:compress_threshold</tt>. The default threshold is 32K.
class Store
- cattr_accessor :logger, :instance_writter => false
+ cattr_accessor :logger, :instance_writer => true
+
attr_reader :silence
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.
+ def initialize (options = nil)
+ @options = options ? options.dup : {}
+ end
+
+ # Get the default options set when the cache was created.
+ def options
+ @options ||= {}
+ end
+
+ # Silence the logger.
def silence!
@silence = true
self
end
+ # Silence the logger within a block.
def mute
previous_silence, @silence = defined?(@silence) && @silence, true
yield
ensure
@silence = previous_silence
@@ -150,119 +206,421 @@
# Setting <tt>:force => true</tt> will force a cache miss:
#
# 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
+ # entry if it is set by call.
+ #
+ # Setting <tt>:race_condition_ttl</tt> will invoke logic on entries set with
+ # an <tt>:expires_in</tt> option. If an entry is found in the cache that is
+ # expired and it has been expired for less than the number of seconds specified
+ # by this option and a block was passed to the method call, then the expiration
+ # future time of the entry in the cache will be updated to that many seconds
+ # in the and the block will be evaluated and written to the cache.
+ #
+ # This is very useful in situations where a cache entry is used very frequently
+ # under heavy load. The first process to find an expired cache entry will then
+ # become responsible for regenerating that entry while other processes continue
+ # to use the slightly out of date entry. This can prevent race conditions where
+ # too many processes are trying to regenerate the entry all at once. If the
+ # process regenerating the entry errors out, the entry will be regenerated
+ # after the specified number of seconds.
+ #
+ # # Set all values to expire after one minute.
+ # cache = ActiveSupport::Cache::MemoryCache.new(:expires_in => 1.minute)
+ #
+ # 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
+ # sleep 1
+ # "new value 1"
+ # end
+ # end
+ #
+ # Thread.new do
+ # val_2 = cache.fetch("foo", :race_condition_ttl => 10) do
+ # "new value 2"
+ # end
+ # end
+ #
+ # # val_1 => "new value 1"
+ # # val_2 => "original value"
+ # # cache.fetch("foo") => "new value 1"
+ #
# Other options will be handled by the specific cache store implementation.
- # Internally, #fetch calls #read, and calls #write on a cache miss.
+ # 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 +:expires_in+
- # option, which tells the memcached server to automatically expire the
- # cache item after a certain period. This options is also supported by
- # FileStore's #read method. We can use this option with #fetch too:
+ # 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, :expires_in => 5.seconds) do
- # "bar"
+ # cache.fetch("foo", :force => true, :raw => true) do
+ # :bar
# end
# cache.fetch("foo") # => "bar"
- # sleep(6)
- # cache.fetch("foo") # => nil
- def fetch(key, options = {}, &block)
- if !options[:force] && value = read(key, options)
- value
+ def fetch(name, options = nil, &block)
+ options = merged_options(options)
+ key = namespaced_key(name, options)
+ entry = instrument(:read, name, options) { read_entry(key, options) } unless options[:force]
+ 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
+
+ if entry
+ entry.value
elsif block_given?
- result = instrument(:generate, key, options, &block)
- write(key, result, options)
+ result = instrument(:generate, name, options, &block)
+ write(name, result, options)
result
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.
#
- # You may also specify additional options via the +options+ argument.
- # The specific cache store implementation will decide what to do with
- # +options+.
+ # Options are passed to the underlying cache implementation.
+ def read(name, options = nil)
+ options = merged_options(options)
+ key = namespaced_key(name, options)
+ instrument(:read, name, options) do
+ entry = read_entry(key, options)
+ if entry
+ if entry.expired?
+ delete_entry(key, options)
+ nil
+ else
+ entry.value
+ end
+ else
+ nil
+ end
+ end
+ end
+
+ # Read multiple values at once from the cache. Options can be passed
+ # in the last argument.
#
- # For example, FileStore supports the +:expires_in+ option, which
- # makes the method return nil for cache items older than the specified
- # period.
- def read(key, options = nil, &block)
- instrument(:read, key, options, &block)
+ # Some cache implementation may optimize this method.
+ #
+ # Returns a hash mapping the names provided to the values found.
+ def read_multi(*names)
+ options = names.extract_options!
+ options = merged_options(options)
+ results = {}
+ names.each do |name|
+ key = namespaced_key(name, options)
+ entry = read_entry(key, options)
+ if entry
+ if entry.expired?
+ delete_entry(key)
+ else
+ results[name] = entry.value
+ end
+ end
+ end
+ results
end
# Writes the given value to the cache, with the given key.
#
# You may also specify additional options via the +options+ argument.
# The specific cache store implementation will decide what to do with
# +options+.
+ def write(name, value, options = nil)
+ options = merged_options(options)
+ instrument(:write, name, options) do
+ entry = Entry.new(value, options)
+ write_entry(namespaced_key(name, options), entry, options)
+ end
+ end
+
+ # Delete an entry in the cache. Returns +true+ if there was an entry to delete.
#
- # For example, MemCacheStore supports the +:expires_in+ option, which
- # tells the memcached server to automatically expire the cache item after
- # a certain period:
+ # Options are passed to the underlying cache implementation.
+ def delete(name, options = nil)
+ options = merged_options(options)
+ instrument(:delete, name) do
+ delete_entry(namespaced_key(name, options), options)
+ end
+ end
+
+ # Return true if the cache contains an entry with this name.
#
- # cache = ActiveSupport::Cache::MemCacheStore.new
- # cache.write("foo", "bar", :expires_in => 5.seconds)
- # cache.read("foo") # => "bar"
- # sleep(6)
- # cache.read("foo") # => nil
- def write(key, value, options = nil, &block)
- instrument(:write, key, options, &block)
+ # Options are passed to the underlying cache implementation.
+ def exist?(name, options = nil)
+ options = merged_options(options)
+ instrument(:exist?, name) do
+ entry = read_entry(namespaced_key(name, options), options)
+ if entry && !entry.expired?
+ true
+ else
+ false
+ end
+ end
end
- def delete(key, options = nil, &block)
- instrument(:delete, key, options, &block)
+ # Delete all entries whose keys match a pattern.
+ #
+ # Options are passed to the underlying cache implementation.
+ #
+ # Not all implementations may support +delete_matched+.
+ def delete_matched(matcher, options = nil)
+ raise NotImplementedError.new("#{self.class.name} does not support delete_matched")
end
- def delete_matched(matcher, options = nil, &block)
- instrument(:delete_matched, matcher.inspect, options, &block)
+ # Increment an integer value in the cache.
+ #
+ # Options are passed to the underlying cache implementation.
+ #
+ # Not all implementations may support +delete_matched+.
+ def increment(name, amount = 1, options = nil)
+ raise NotImplementedError.new("#{self.class.name} does not support increment")
end
- def exist?(key, options = nil, &block)
- instrument(:exist?, key, options, &block)
+ # Increment an integer value in the cache.
+ #
+ # Options are passed to the underlying cache implementation.
+ #
+ # Not all implementations may support +delete_matched+.
+ def decrement(name, amount = 1, options = nil)
+ raise NotImplementedError.new("#{self.class.name} does not support decrement")
end
- def increment(key, amount = 1)
- if num = read(key)
- write(key, num + amount)
- else
- nil
- end
+ # Cleanup the cache by removing expired entries. Not all cache implementations may
+ # support this method.
+ #
+ # Options are passed to the underlying cache implementation.
+ #
+ # Not all implementations may support +delete_matched+.
+ def cleanup(options = nil)
+ raise NotImplementedError.new("#{self.class.name} does not support cleanup")
end
- def decrement(key, amount = 1)
- if num = read(key)
- write(key, num - amount)
- else
- nil
- end
+ # Clear the entire cache. Not all cache implementations may support this method.
+ # You should be careful with this method since it could affect other processes
+ # if you are using a shared cache.
+ #
+ # Options are passed to the underlying cache implementation.
+ #
+ # Not all implementations may support +delete_matched+.
+ 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.
+ 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?('^')
+ source = source[1, source.length]
+ else
+ source = ".*#{source[0, source.length]}"
+ end
+ Regexp.new("^#{Regexp.escape(prefix)}:#{source}", pattern.options)
+ else
+ pattern
+ end
+ end
+
+ # 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.
+ def write_entry(key, entry, options) # :nodoc:
+ raise NotImplementedError.new
+ end
+
+ # Delete an entry from the cache implementation. Subclasses must implement this method.
+ def delete_entry(key, options) # :nodoc:
+ raise NotImplementedError.new
+ end
+
private
- def expires_in(options)
- expires_in = options && options[:expires_in]
- raise ":expires_in must be a number" if expires_in && !expires_in.is_a?(Numeric)
- expires_in || 0
+ # Merge the default options with ones specific to a method call.
+ def merged_options(call_options) # :nodoc:
+ if call_options
+ options.merge(call_options)
+ else
+ options.dup
+ end
end
- def instrument(operation, key, options)
+ # Expand a key to be a consistent string value. If the object responds to +cache_key+,
+ # it will be called. Otherwise, the to_param method will be called. If the key is a
+ # Hash, the keys will be sorted alphabetically.
+ def expanded_key(key) # :nodoc:
+ if key.respond_to?(:cache_key)
+ key = key.cache_key.to_s
+ elsif key.is_a?(Array)
+ if key.size > 1
+ key.collect{|element| expanded_key(element)}.to_param
+ else
+ key.first.to_param
+ end
+ elsif key.is_a?(Hash)
+ key = key.to_a.sort{|a,b| a.first.to_s <=> b.first.to_s}.collect{|k,v| "#{k}=#{v}"}.to_param
+ else
+ key = key.to_param
+ end
+ end
+
+ # Prefix a key with the namespace. The two values 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
+ key
+ end
+
+ def instrument(operation, key, options = nil)
log(operation, key, options)
if self.class.instrument
payload = { :key => key }
payload.merge!(options) if options.is_a?(Hash)
- ActiveSupport::Notifications.instrument("active_support.cache_#{operation}", payload){ yield }
+ ActiveSupport::Notifications.instrument("cache_#{operation}.active_support", payload){ yield }
else
yield
end
end
- def log(operation, key, options)
- return unless logger && !silence?
- logger.debug("Cache #{operation}: #{key}#{options ? " (#{options.inspect})" : ""}")
+ 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
+
+ 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])
+ entry
+ end
+ end
+
+ # 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
+ if should_compress?(value, options)
+ @value = Zlib::Deflate.deflate(Marshal.dump(value))
+ @compressed = true
+ else
+ @value = value
+ end
+ else
+ @value = nil
+ 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 @value
+ val = compressed? ? Marshal.load(Zlib::Inflate.inflate(@value)) : @value
+ unless val.frozen?
+ val.freeze rescue nil
+ end
+ val
+ end
+ 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.
+ def expired?
+ if @expires_in && @created_at + @expires_in <= Time.now.to_f
+ true
+ else
+ false
+ end
+ end
+
+ # Set a new time to live on the entry so it expires at the given time.
+ def expires_at=(time)
+ if time
+ @expires_in = time.to_f - @created_at
+ else
+ @expires_in = nil
+ end
+ end
+
+ # Seconds since the epoch when the cache entry will expire.
+ def expires_at
+ @expires_in ? @created_at + @expires_in : nil
+ end
+
+ # Get the size of the cached value. This could be less than value.size
+ # if the data is compressed.
+ def size
+ if @value.nil?
+ 0
+ elsif @value.respond_to?(:bytesize)
+ @value.bytesize
+ else
+ Marshal.dump(@value).bytesize
+ end
+ end
+
+ private
+ def should_compress?(value, options)
+ if options[:compress] && value
+ unless value.is_a?(Numeric)
+ compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT
+ serialized_value = value.is_a?(String) ? value : Marshal.dump(value)
+ return true if serialized_value.size >= compress_threshold
+ end
+ end
+ false
end
end
end
end