class ActiveSupport::Cache::Store
An abstract cache store class. There are multiple cache store 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.
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 Ruby object that is supported by its coder
‘s dump
and load
methods.
cache = ActiveSupport::Cache::MemoryStore.new cache.read('city') # => nil cache.write('city', "Duckburgh") cache.read('city') # => "Duckburgh" cache.write('not serializable', Proc.new {}) # => TypeError
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
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 = -> { @last_mod_time } # Set the namespace to a variable @last_mod_time = Time.now # Invalidate the entire cache by changing namespace
Attributes
Public Class Methods
Source
# File lib/active_support/cache.rb, line 211 def initialize(options = nil) @options = options ? normalize_options(options) : {} @options[:compress] = true unless @options.key?(:compress) @options[:compress_threshold] = DEFAULT_COMPRESS_LIMIT unless @options.key?(:compress_threshold) @coder = @options.delete(:coder) { default_coder } || NullCoder @coder_supports_compression = @coder.respond_to?(:dump_compressed) end
Creates a new cache.
Options¶ ↑
-
:namespace
- Sets the namespace for the cache. This option is especially useful if your application shares a cache with other applications. -
:coder
- Replaces the default cache entry serialization mechanism with a custom one. Thecoder
must respond todump
andload
. Using a custom coder disables automatic compression.
Any other specified options are treated as default options for the relevant cache operations, such as read
, write
, and fetch
.
Private Class Methods
Source
# File lib/active_support/cache.rb, line 190 def ensure_connection_pool_added! require "connection_pool" rescue LoadError => e $stderr.puts "You don't have connection_pool installed in your application. Please add it to your Gemfile and run bundle install" raise e end
Source
# File lib/active_support/cache.rb, line 183 def retrieve_pool_options(options) {}.tap do |pool_options| pool_options[:size] = options.delete(:pool_size) if options[:pool_size] pool_options[:timeout] = options.delete(:pool_timeout) if options[:pool_timeout] end end
Public Instance Methods
Source
# File lib/active_support/cache.rb, line 582 def cleanup(options = nil) raise NotImplementedError.new("#{self.class.name} does not support cleanup") end
Cleans up the cache by removing expired entries.
Options are passed to the underlying cache implementation.
Some implementations may not support this method.
Source
# File lib/active_support/cache.rb, line 592 def clear(options = nil) raise NotImplementedError.new("#{self.class.name} does not support clear") end
Clears the entire cache. Be careful with this method since it could affect other processes if shared cache is being used.
The options hash is passed to the underlying cache implementation.
Some implementations may not support this method.
Source
# File lib/active_support/cache.rb, line 573 def decrement(name, amount = 1, options = nil) raise NotImplementedError.new("#{self.class.name} does not support decrement") end
Decrements an integer value in the cache.
Options are passed to the underlying cache implementation.
Some implementations may not support this method.
Source
# File lib/active_support/cache.rb, line 514 def delete(name, options = nil) options = merged_options(options) instrument(:delete, name) do delete_entry(normalize_key(name, options), **options) end end
Deletes an entry in the cache. Returns true
if an entry is deleted.
Options are passed to the underlying cache implementation.
Source
# File lib/active_support/cache.rb, line 555 def delete_matched(matcher, options = nil) raise NotImplementedError.new("#{self.class.name} does not support delete_matched") end
Deletes all entries with keys matching the pattern.
Options are passed to the underlying cache implementation.
Some implementations may not support this method.
Source
# File lib/active_support/cache.rb, line 525 def delete_multi(names, options = nil) options = merged_options(options) names.map! { |key| normalize_key(key, options) } instrument :delete_multi, names do delete_multi_entries(names, **options) end end
Deletes multiple entries in the cache.
Options are passed to the underlying cache implementation.
Source
# File lib/active_support/cache.rb, line 537 def exist?(name, options = nil) options = merged_options(options) instrument(:exist?, name) do |payload| entry = read_entry(normalize_key(name, options), **options, event: payload) (entry && !entry.expired? && !entry.mismatched?(normalize_version(name, options))) || false end end
Returns true
if the cache contains an entry for the given key.
Options are passed to the underlying cache implementation.
Source
# File lib/active_support/cache.rb, line 321 def fetch(name, options = nil, &block) if block_given? options = merged_options(options) key = normalize_key(name, options) entry = nil instrument(:read, name, options) do |payload| cached_entry = read_entry(key, **options, event: payload) unless options[:force] entry = handle_expired_entry(cached_entry, key, options) entry = nil if entry && entry.mismatched?(normalize_version(name, options)) payload[:super_operation] = :fetch if payload payload[:hit] = !!entry if payload end if entry get_entry_value(entry, name, options) else save_block_result_to_cache(name, options, &block) end elsif options && options[:force] raise ArgumentError, "Missing block: Calling `Cache#fetch` with `force: true` requires a block." 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.
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.fetch('city') # => nil cache.fetch('city') do 'Duckburgh' end cache.fetch('city') # => "Duckburgh"
Options¶ ↑
Internally, fetch
calls read_entry
, and calls write_entry
on a cache miss. Thus, fetch
supports the same options as read
and write
. Additionally, fetch
supports the following options:
-
force: true
- Forces a cache “miss,” meaning we treat the cache value as missing even if it’s present. Passing a block is required whenforce
is true so this always results in a cache write.cache.write('today', 'Monday') cache.fetch('today', force: true) { 'Tuesday' } # => 'Tuesday' cache.fetch('today', force: true) # => ArgumentError
The
:force
option is useful when you’re calling some other method to ask whether you should force a cache write. Otherwise, it’s clearer to just callwrite
. -
skip_nil: true
- Prevents caching a nil result:cache.fetch('foo') { nil } cache.fetch('bar', skip_nil: true) { nil } cache.exist?('foo') # => true cache.exist?('bar') # => false
-
:race_condition_ttl
- Specifies the number of seconds during which an expired value can be reused while a new value is being generated. This can be used to prevent race conditions when cache entries expire, by preventing multiple processes from simultaneously regenerating the same entry (also known as the dog pile effect).When a process encounters a cache entry that has expired less than
:race_condition_ttl
seconds ago, it will bump the expiration time by:race_condition_ttl
seconds before generating a new value. During this extended time window, while the process generates a new value, other processes will continue to use the old value. After the first process writes the new value, other processes will then use it.If the first process errors out while generating a new value, another process can try to generate a new value after the extended time window has elapsed.
# Set all values to expire after one minute. cache = ActiveSupport::Cache::MemoryStore.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.seconds) do sleep 1 'new value 1' end end Thread.new do val_2 = cache.fetch('foo', race_condition_ttl: 10.seconds) do 'new value 2' end end cache.fetch('foo') # => "original value" sleep 10 # First thread extended the life of cache by another 10 seconds cache.fetch('foo') # => "new value 1" val_1 # => "new value 1" val_2 # => "original value"
Source
# File lib/active_support/cache.rb, line 447 def fetch_multi(*names) raise ArgumentError, "Missing block: `Cache#fetch_multi` requires a block." unless block_given? options = names.extract_options! options = merged_options(options) instrument :read_multi, names, options do |payload| reads = read_multi_entries(names, **options) writes = {} ordered = names.index_with do |name| reads.fetch(name) { writes[name] = yield(name) } end payload[:hits] = reads.keys payload[:super_operation] = :fetch_multi write_multi(writes, options) ordered end end
Fetches data from the cache, using the given keys. If there is data in the cache with the given keys, then that data is returned. Otherwise, the supplied block is called for each key for which there was no data, and the result will be written to the cache and returned. Therefore, you need to pass a block that returns the data to be written to the cache. If you do not want to write the cache when the cache is not found, use read_multi
.
Returns a hash with the data for each of the names. For example:
cache.write("bim", "bam") cache.fetch_multi("bim", "unknown_key") do |key| "Fallback value for key: #{key}" end # => { "bim" => "bam", # "unknown_key" => "Fallback value for key: unknown_key" }
Options are passed to the underlying cache implementation. For example:
cache.fetch_multi("fizz", expires_in: 5.seconds) do |key| "buzz" end # => {"fizz"=>"buzz"} cache.read("fizz") # => "buzz" sleep(6) cache.read("fizz") # => nil
Source
# File lib/active_support/cache.rb, line 564 def increment(name, amount = 1, options = nil) raise NotImplementedError.new("#{self.class.name} does not support increment") end
Increments an integer value in the cache.
Options are passed to the underlying cache implementation.
Some implementations may not support this method.
Source
# File lib/active_support/cache.rb, line 227 def mute previous_silence, @silence = defined?(@silence) && @silence, true yield ensure @silence = previous_silence end
Silences the logger within a block.
Source
# File lib/active_support/cache.rb, line 362 def read(name, options = nil) options = merged_options(options) key = normalize_key(name, options) version = normalize_version(name, options) instrument(:read, name, options) do |payload| entry = read_entry(key, **options, event: payload) if entry if entry.expired? delete_entry(key, **options) payload[:hit] = false if payload nil elsif entry.mismatched?(version) payload[:hit] = false if payload nil else payload[:hit] = true if payload entry.value end else payload[:hit] = false if payload nil end end end
Reads 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.
Note, if data was written with the :expires_in
or :version
options, both of these conditions are applied before the data is returned.
Options¶ ↑
-
:version
- Specifies a version for the cache entry. If the cached version does not match the requested version, the read will be treated as a cache miss. This feature is used to support recyclable cache keys.
Other options will be handled by the specific cache store implementation.
Source
# File lib/active_support/cache.rb, line 395 def read_multi(*names) options = names.extract_options! options = merged_options(options) instrument :read_multi, names, options do |payload| read_multi_entries(names, **options, event: payload).tap do |results| payload[:hits] = results.keys end end end
Reads multiple values at once from the cache. Options can be passed in the last argument.
Some cache implementation may optimize this method.
Returns a hash mapping the names provided to the values found.
Source
# File lib/active_support/cache.rb, line 221 def silence! @silence = true self end
Silences the logger.
Source
# File lib/active_support/cache.rb, line 502 def write(name, value, options = nil) options = merged_options(options) instrument(:write, name, options) do entry = Entry.new(value, **options.merge(version: normalize_version(name, options))) write_entry(normalize_key(name, options), entry, **options) end end
Writes the value to the cache with the key. The value must be supported by the coder
‘s dump
and load
methods.
By default, cache entries larger than 1kB are compressed. Compression allows more data to be stored in the same memory footprint, leading to fewer cache evictions and higher hit rates.
Options¶ ↑
-
compress: false
- Disables compression of the cache entry. -
:compress_threshold
- The compression threshold, specified in bytes. Cache entries larger than this threshold will be compressed. Defaults to1.kilobyte
. -
:expires_in
- Sets a relative expiration time for the cache entry, specified in seconds.:expire_in
and:expired_in
are aliases for:expires_in
.cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 5.minutes) cache.write(key, value, expires_in: 1.minute) # Set a lower value for one entry
-
:expires_at
- Sets an absolute expiration time for the cache entry.cache = ActiveSupport::Cache::MemoryStore.new cache.write(key, value, expires_at: Time.now.at_end_of_hour)
-
:version
- Specifies a version for the cache entry. When reading from the cache, if the cached version does not match the requested version, the read will be treated as a cache miss. This feature is used to support recyclable cache keys.
Other options will be handled by the specific cache store implementation.
Source
# File lib/active_support/cache.rb, line 407 def write_multi(hash, options = nil) options = merged_options(options) instrument :write_multi, hash, options do |payload| entries = hash.each_with_object({}) do |(name, value), memo| memo[normalize_key(name, options)] = Entry.new(value, **options.merge(version: normalize_version(name, options))) end write_multi_entries entries, **options end end
Cache
Storage API to write multiple values at once.
Private Instance Methods
Source
# File lib/active_support/cache.rb, line 597 def default_coder Coders[Cache.format_version] end
Source
# File lib/active_support/cache.rb, line 674 def delete_entry(key, **options) raise NotImplementedError.new end
Deletes an entry from the cache implementation. Subclasses must implement this method.
Source
# File lib/active_support/cache.rb, line 680 def delete_multi_entries(entries, **options) entries.count { |key| delete_entry(key, **options) } end
Deletes multiples entries in the cache implementation. Subclasses MAY implement this method.
Source
# File lib/active_support/cache.rb, line 641 def deserialize_entry(payload) payload.nil? ? nil : @coder.load(payload) end
Source
# File lib/active_support/cache.rb, line 747 def expanded_key(key) return key.cache_key.to_s if key.respond_to?(:cache_key) case key when Array if key.size > 1 key.collect { |element| expanded_key(element) } else expanded_key(key.first) end when Hash key.collect { |k, v| "#{k}=#{v}" }.sort! else key end.to_param end
Expands key to be a consistent string value. Invokes cache_key
if object responds to cache_key
. Otherwise, to_param
method will be called. If the key is a Hash
, then keys will be sorted alphabetically.
Source
# File lib/active_support/cache.rb, line 768 def expanded_version(key) case when key.respond_to?(:cache_version) then key.cache_version.to_param when key.is_a?(Array) then key.map { |element| expanded_version(element) }.tap(&:compact!).to_param when key.respond_to?(:to_a) then expanded_version(key.to_a) end end
Source
# File lib/active_support/cache.rb, line 802 def get_entry_value(entry, name, options) instrument(:fetch_hit, name, options) { } entry.value end
Source
# File lib/active_support/cache.rb, line 786 def handle_expired_entry(entry, key, options) if entry && entry.expired? race_ttl = options[:race_condition_ttl].to_i if (race_ttl > 0) && (Time.now.to_f - entry.expires_at <= race_ttl) # When an entry has a positive :race_condition_ttl defined, put the stale entry back into the cache # for a brief period while the entry is being recalculated. entry.expires_at = Time.now.to_f + race_ttl write_entry(key, entry, expires_in: race_ttl * 2) else delete_entry(key, **options) end entry = nil end entry end
Source
# File lib/active_support/cache.rb, line 776 def instrument(operation, key, options = nil) if logger && logger.debug? && !silence? logger.debug "Cache #{operation}: #{normalize_key(key, options)}#{options.blank? ? "" : " (#{options.inspect})"}" end payload = { key: key, store: self.class.name } payload.merge!(options) if options.is_a?(Hash) ActiveSupport::Notifications.instrument("cache_#{operation}.active_support", payload) { yield(payload) } end
Source
# File lib/active_support/cache.rb, line 605 def key_matcher(pattern, options) # :doc: 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
Adds 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.
Source
# File lib/active_support/cache.rb, line 685 def merged_options(call_options) if call_options call_options = normalize_options(call_options) if options.empty? call_options else options.merge(call_options) end else options end end
Merges the default options with ones specific to a method call.
Source
# File lib/active_support/cache.rb, line 725 def namespace_key(key, options = nil) options = merged_options(options) namespace = options[:namespace] if namespace.respond_to?(:call) namespace = namespace.call end if key && key.encoding != Encoding::UTF_8 key = key.dup.force_encoding(Encoding::UTF_8) end if namespace "#{namespace}:#{key}" else key end end
Prefix the key with a namespace string:
namespace_key 'foo', namespace: 'cache' # => 'cache:foo'
With a namespace block:
namespace_key 'foo', namespace: -> { 'cache' } # => 'cache:foo'
Source
# File lib/active_support/cache.rb, line 712 def normalize_key(key, options = nil) namespace_key expanded_key(key), options end
Expands and namespaces the cache key. May be overridden by cache stores to do additional normalization.
Source
# File lib/active_support/cache.rb, line 699 def normalize_options(options) options = options.dup OPTION_ALIASES.each do |canonical_name, aliases| alias_key = aliases.detect { |key| options.key?(key) } options[canonical_name] ||= options[alias_key] if alias_key options.except!(*aliases) end options end
Normalize aliased options to their canonical form
Source
# File lib/active_support/cache.rb, line 764 def normalize_version(key, options = nil) (options && options[:version].try(:to_param)) || expanded_version(key) end
Source
# File lib/active_support/cache.rb, line 622 def read_entry(key, **options) raise NotImplementedError.new end
Reads an entry from the cache implementation. Subclasses must implement this method.
Source
# File lib/active_support/cache.rb, line 647 def read_multi_entries(names, **options) names.each_with_object({}) do |name, results| key = normalize_key(name, options) entry = read_entry(key, **options) next unless entry version = normalize_version(name, options) if entry.expired? delete_entry(key, **options) elsif !entry.mismatched?(version) results[name] = entry.value end end end
Reads multiple entries from the cache implementation. Subclasses MAY implement this method.
Source
# File lib/active_support/cache.rb, line 807 def save_block_result_to_cache(name, options) result = instrument(:generate, name, options) do yield(name) end write(name, result, options) unless result.nil? && options[:skip_nil] result end
Source
# File lib/active_support/cache.rb, line 632 def serialize_entry(entry, **options) options = merged_options(options) if @coder_supports_compression && options[:compress] @coder.dump_compressed(entry, options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT) else @coder.dump(entry) end end
Source
# File lib/active_support/cache.rb, line 628 def write_entry(key, entry, **options) raise NotImplementedError.new end
Writes an entry to the cache implementation. Subclasses must implement this method.
Source
# File lib/active_support/cache.rb, line 666 def write_multi_entries(hash, **options) hash.each do |key, entry| write_entry key, entry, **options end end
Writes multiple entries to the cache implementation. Subclasses MAY implement this method.