ActiveSupport::Cache::Store (original) (raw)

Active Support 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") # => true
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

Methods

C

• cleanup,
• clear

D

• decrement,
• delete,
• delete_matched,
• delete_multi

E

• exist?

F

• fetch,
• fetch_multi

I

• increment

K

• key_matcher

M

• mute

N

• new

R

• read,
• read_multi

S

• silence!

W

• write,
• write_multi

Attributes

Class Public methods

new(options = nil)Link

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.

:serializer

The serializer for cached values. Must respond to dump and load.

The default serializer depends on the cache format version (set via config.active_support.cache_format_version when using Rails). The default serializer for each format version includes a fallback mechanism to deserialize values from any format version. This behavior makes it easy to migrate between format versions without invalidating the entire cache.

You can also specify serializer: :message_pack to use a preconfigured serializer based on ActiveSupport::MessagePack. The :message_pack serializer includes the same deserialization fallback mechanism, allowing easy migration from (or to) the default serializer. The :message_pack serializer may improve performance, but it requires the msgpack gem.

:compressor

The compressor for serialized cache values. Must respond to deflate and inflate.

The default compressor is Zlib. To define a new custom compressor that also decompresses old cache entries, you can check compressed values for Zlib’s "\x78" signature:

module MyCompressor
  def self.deflate(dumped)
    # compression logic... (make sure result does not start with "\x78"!)
  end

  def self.inflate(compressed)
    if compressed.start_with?("\x78")
      Zlib.inflate(compressed)
    else
      # decompression logic...
    end
  end
end

ActiveSupport::Cache.lookup_store(:redis_cache_store, compressor: MyCompressor)

:coder

The coder for serializing and (optionally) compressing cache entries. Must respond to dump and load.

The default coder composes the serializer and compressor, and includes some performance optimizations. If you only need to override the serializer or compressor, you should specify the :serializer or :compressor options instead.

If the store can handle cache entries directly, you may also specify coder: nil to omit the serializer, compressor, and coder. For example, if you are using ActiveSupport::Cache::MemoryStore and can guarantee that cache values will not be mutated, you can specify coder: nil to avoid the overhead of safeguarding against mutation.

The :coder option is mutually exclusive with the :serializer and :compressor options. Specifying them together will raise an ArgumentError.

Any other specified options are treated as default options for the relevant cache operations, such as read, write, and fetch.

Source: show | on GitHub

def initialize(options = nil) @options = options ? validate_options(normalize_options(options)) : {}

@options[:compress] = true unless @options.key?(:compress) @options[:compress_threshold] ||= DEFAULT_COMPRESS_LIMIT

@coder = @options.delete(:coder) do legacy_serializer = Cache.format_version < 7.1 && !@options[:serializer] serializer = @options.delete(:serializer) || default_serializer serializer = Cache::SerializerWithFallback[serializer] if serializer.is_a?(Symbol) compressor = @options.delete(:compressor) { Zlib }

Cache::Coder.new(serializer, compressor, legacy_serializer: legacy_serializer)

end

@coder ||= Cache::SerializerWithFallback[:passthrough]

@coder_supports_compression = @coder.respond_to?(:dump_compressed) end

Instance Public methods

cleanup(options = nil)Link

Cleans up the cache by removing expired entries.

Options are passed to the underlying cache implementation.

Some implementations may not support this method.

Source: show | on GitHub

def cleanup(options = nil) raise NotImplementedError.new("#{self.class.name} does not support cleanup") end

clear(options = nil)Link

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: show | on GitHub

def clear(options = nil) raise NotImplementedError.new("#{self.class.name} does not support clear") end

decrement(name, amount = 1, options = nil)Link

Decrements an integer value in the cache.

Options are passed to the underlying cache implementation.

Some implementations may not support this method.

Source: show | on GitHub

def decrement(name, amount = 1, options = nil) raise NotImplementedError.new("#{self.class.name} does not support decrement") end

delete(name, options = nil)Link

Deletes an entry in the cache. Returns true if an entry is deleted and false otherwise.

Options are passed to the underlying cache implementation.

Source: show | on GitHub

def delete(name, options = nil) options = merged_options(options) key = normalize_key(name, options)

instrument(:delete, key, options) do delete_entry(key, **options) end end

delete_matched(matcher, options = nil)Link

Deletes all entries with keys matching the pattern.

Options are passed to the underlying cache implementation.

Some implementations may not support this method.

Source: show | on GitHub

def delete_matched(matcher, options = nil) raise NotImplementedError.new("#{self.class.name} does not support delete_matched") end

delete_multi(names, options = nil)Link

Deletes multiple entries in the cache. Returns the number of deleted entries.

Options are passed to the underlying cache implementation.

Source: show | on GitHub

def delete_multi(names, options = nil) return 0 if names.empty?

options = merged_options(options) names.map! { |key| normalize_key(key, options) }

instrument_multi(:delete_multi, names, options) do delete_multi_entries(names, **options) end end

exist?(name, options = nil)Link

Returns true if the cache contains an entry for the given key.

Options are passed to the underlying cache implementation.

Source: show | on GitHub

def exist?(name, options = nil) options = merged_options(options) key = normalize_key(name, options)

instrument(:exist?, key) do |payload| entry = read_entry(key, **options, event: payload) (entry && !entry.expired? && !entry.mismatched?(normalize_version(name, options))) || false end end

fetch(name, options = nil, &block)Link

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 when force 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 call write.

• 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 second.  
cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 1)  
cache.write("foo", "original value")  
val_1 = nil  
val_2 = nil  
p cache.read("foo") # => "original value"  
sleep 1 # wait until the cache expires  
t1 = Thread.new do  
  # fetch does the following:  
  # 1. gets an recent expired entry  
  # 2. extends the expiry by 2 seconds (race_condition_ttl)  
  # 3. regenerates the new value  
  val_1 = cache.fetch("foo", race_condition_ttl: 2) do  
    sleep 1  
    "new value 1"  
  end  
end  
# Wait until t1 extends the expiry of the entry  
# but before generating the new value  
sleep 0.1  
val_2 = cache.fetch("foo", race_condition_ttl: 2) do  
  # This block won't be executed because t1 extended the expiry  
  "new value 2"  
end  
t1.join  
p val_1 # => "new value 1"  
p val_2 # => "original value"  
p cache.fetch("foo") # => "new value 1"  
# The entry requires 3 seconds to expire (expires_in + race_condition_ttl)  
# We have waited 2 seconds already (sleep(1) + t1.join) thus we need to wait 1  
# more second to see the entry expire.  
sleep 1  
p cache.fetch("foo") # => nil  

Dynamic Options

In some cases it may be necessary to dynamically compute options based on the cached value. To support this, an ActiveSupport::Cache::WriteOptions instance is passed as the second argument to the block. For example:

cache.fetch("authentication-token:#{user.id}") do |key, options|
  token = authenticate_to_service
  options.expires_at = token.expires_at
  token
end

Source: show | on GitHub

def fetch(name, options = nil, &block) if block_given? options = merged_options(options) key = normalize_key(name, options)

entry = nil
unless options[:force]
  instrument(:read, key, options) do |payload|
    cached_entry = read_entry(key, **options, event: payload)
    entry = handle_expired_entry(cached_entry, key, options)
    if entry
      if entry.mismatched?(normalize_version(name, options))
        entry = nil
      else
        begin
          entry.value
        rescue DeserializationError
          entry = nil
        end
      end
    end
    payload[:super_operation] = :fetch if payload
    payload[:hit] = !!entry if payload
  end
end

if entry
  get_entry_value(entry, name, options)
else
  save_block_result_to_cache(name, key, 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

fetch_multi(*names)Link

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" }

You may also specify additional options via the options argument. See fetch for details. Other 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: show | on GitHub

def fetch_multi(*names) raise ArgumentError, "Missing block: Cache#fetch_multi requires a block." unless block_given? return {} if names.empty?

options = names.extract_options! options = merged_options(options) keys = names.map { |name| normalize_key(name, options) } writes = {} ordered = instrument_multi :read_multi, keys, options do |payload| if options[:force] reads = {} else reads = read_multi_entries(names, **options) end

ordered = names.index_with do |name|
  reads.fetch(name) { writes[name] = yield(name) }
end
writes.compact! if options[:skip_nil]

payload[:hits] = reads.keys.map { |name| normalize_key(name, options) }
payload[:super_operation] = :fetch_multi

ordered

end

write_multi(writes, options)

ordered end

increment(name, amount = 1, options = nil)Link

Increments an integer value in the cache.

Options are passed to the underlying cache implementation.

Some implementations may not support this method.

Source: show | on GitHub

def increment(name, amount = 1, options = nil) raise NotImplementedError.new("#{self.class.name} does not support increment") end

mute()Link

Silences the logger within a block.

Source: show | on GitHub

def mute previous_silence, @silence = @silence, true yield ensure @silence = previous_silence end

read(name, options = nil)Link

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

• :namespace - Replace the store namespace for this call.
• :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: show | on GitHub

def read(name, options = nil) options = merged_options(options) key = normalize_key(name, options) version = normalize_version(name, options)

instrument(:read, key, 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
    begin
      entry.value
    rescue DeserializationError
      payload[:hit] = false
      nil
    end
  end
else
  payload[:hit] = false if payload
  nil
end

end end

read_multi(*names)Link

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: show | on GitHub

def read_multi(*names) return {} if names.empty?

options = names.extract_options! options = merged_options(options) keys = names.map { |name| normalize_key(name, options) }

instrument_multi :read_multi, keys, options do |payload| read_multi_entries(names, **options, event: payload).tap do |results| payload[:hits] = results.keys.map { |name| normalize_key(name, options) } end end end

silence!()Link

Silences the logger.

write(name, value, options = nil)Link

Writes the value to the cache with the key. The value must be supported by the coder‘s dump and load methods.

Returns true if the write succeeded, nil if there was an error talking to the cache backend, or false if the write failed for another reason.

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 to 1.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: show | on GitHub

def write(name, value, options = nil) options = merged_options(options) key = normalize_key(name, options)

instrument(:write, key, options) do entry = Entry.new(value, **options.merge(version: normalize_version(name, options))) write_entry(key, entry, **options) end end

write_multi(hash, options = nil)Link

Cache Storage API to write multiple values at once.

Source: show | on GitHub

def write_multi(hash, options = nil) return hash if hash.empty?

options = merged_options(options) normalized_hash = hash.transform_keys { |key| normalize_key(key, options) }

instrument_multi :write_multi, normalized_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

Instance Private methods

key_matcher(pattern, options)Link

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: show | on GitHub

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