Class: ActiveSupport::Cache::MemCacheStore

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, `Store`
Instance Chain: self, `Strategy::LocalCache`, `Store`
Inherits:	ActiveSupport::Cache::Store `::Object` ActiveSupport::Cache::Store ActiveSupport::Cache::MemCacheStore
Defined in:	activesupport/lib/active_support/cache/mem_cache_store.rb

Overview

Memcached Cache Store

A cache store implementation which stores data in Memcached: memcached.org

This is currently the most popular cache store for production websites.

Special features:

Clustering and load balancing. One can specify multiple memcached servers, and MemCacheStore will load balance between all available servers. If a server goes down, then MemCacheStore will ignore it until it comes back up.

MemCacheStore implements the Strategy::LocalCache strategy which implements an in-memory cache inside of a block.

Constant Summary

ESCAPE_KEY_CHARS =
# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 45
```
/[\x00-\x20%\x7F-\xFF]/n
```
KEY_MAX_SIZE =
# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 44
```
250
```
OVERRIDDEN_OPTIONS =

These options represent behavior overridden by this implementation and should not be allowed to get down to the Dalli client

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 35
```
UNIVERSAL_OPTIONS
```

`Store` - Inherited

DEFAULT_POOL_OPTIONS

Class Attribute Summary

.supports_cache_versioning? ⇒ Boolean readonly

Advertise cache versioning support.

`Store` - Inherited

.logger, .raise_on_invalid_cache_expiration_time

Class Method Summary

.new(*addresses) ⇒ MemCacheStore constructor

Creates a new MemCacheStore object, with the given memcached server addresses.
.build_mem_cache(*addresses) Internal use only

Creates a new Dalli::Client instance with specified addresses and options.

`Store` - Inherited

.new	Creates a new cache.
.retrieve_pool_options

Instance Attribute Summary

`Store` - Inherited

#logger, #options, #raise_on_invalid_cache_expiration_time,
#silence?	Alias for Store#silence.

Instance Method Summary

#clear(options = nil)

Clear the entire cache on all memcached servers.
#decrement(name, amount = 1, options = nil)

Decrement a cached integer value using the memcached decr atomic operator.
#increment(name, amount = 1, options = nil)

Increment a cached integer value using the memcached incr atomic operator.
#inspect
#stats

Get the statistics from the memcached servers.
#write(name, value, options = nil)

Behaves the same as Store#write, but supports additional options specific to memcached.
#delete_entry(key, **options) private

Delete an entry from the cache.
#deserialize_entry(payload, raw: false) private
#normalize_key(key, options) private

Memcache keys are binaries.
#read_entry(key, **options) private

Read an entry from the cache.
#read_multi_entries(names, **options) private

Reads multiple entries from the cache implementation.
#read_serialized_entry(key, **options) private
#rescue_error_with(fallback) private
#serialize_entry(entry, raw: false, **options) private
#write_entry(key, entry, **options) private

Write an entry to the cache.
#write_serialized_entry(key, payload, **options) private

`Strategy::LocalCache` - Included

#middleware	Middleware class can be inserted as a `::Rack` handler to be local cache for the duration of request.
#with_local_cache	Use a local cache for the duration of block.
#bypass_local_cache, #delete_entry, #local_cache, #local_cache_key, #read_multi_entries, #read_serialized_entry, #use_temporary_local_cache, #write_cache_value, #write_serialized_entry, #cleanup, #clear, #decrement, #delete_matched, #increment

`Store` - Inherited

#cleanup	Cleans up the cache by removing expired entries.
#clear	Clears the entire cache.
#decrement	Decrements an integer value in the cache.
#delete	Deletes an entry in the cache.
#delete_matched	Deletes all entries with keys matching the pattern.
#delete_multi	Deletes multiple entries in the cache.
#exist?	Returns `true` if the cache contains an entry for the given key.
#fetch	Fetches data from the cache, using the given key.
#fetch_multi	Fetches data from the cache, using the given keys.
#increment	Increments an integer value in the cache.
#mute	Silences the logger within a block.
#read	Reads data from the cache, using the given key.
#read_multi	Reads multiple values at once from the cache.
#silence,
#silence!	Silences the logger.
#write	Writes the value to the cache with the key.
#write_multi	`::ActiveSupport::Cache` Storage API to write multiple values at once.
#_instrument, #default_serializer,
#delete_entry	Deletes an entry from the cache implementation.
#delete_multi_entries	Deletes multiples entries in the cache implementation.
#deserialize_entry,
#expanded_key	Expands key to be a consistent string value.
#expanded_version, #get_entry_value, #handle_expired_entry, #handle_invalid_expires_in, #instrument, #instrument_multi,
#key_matcher	Adds the namespace defined in the options to a pattern designed to match keys.
#merged_options	Merges the default options with ones specific to a method call.
#namespace_key	Prefix the key with a namespace string:
#normalize_key	Expands and namespaces the cache key.
#normalize_options	Normalize aliased options to their canonical form.
#normalize_version,
#read_entry	Reads an entry from the cache implementation.
#read_multi_entries	Reads multiple entries from the cache implementation.
#save_block_result_to_cache, #serialize_entry, #validate_options,
#write_entry	Writes an entry to the cache implementation.
#write_multi_entries	Writes multiple entries to the cache implementation.
#new_entry

Constructor Details

.new(*addresses) ⇒ `MemCacheStore`

Creates a new MemCacheStore object, with the given memcached server addresses. Each address is either a host name, or a host-with-port string in the form of “host_name:port”. For example:

ActiveSupport::Cache::MemCacheStore.new("localhost", "server-downstairs.localnetwork:8229")

If no addresses are provided, but ENV['MEMCACHE_SERVERS'] is defined, it will be used instead. Otherwise, MemCacheStore will connect to localhost:11211 (the default memcached port).

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 77


def initialize(*addresses)
  addresses = addresses.flatten
  options = addresses.extract_options!
  if options.key?(:cache_nils)
    options[:skip_nil] = !options.delete(:cache_nils)
  end
  super(options)

  unless [String, Dalli::Client, NilClass].include?(addresses.first.class)
    raise ArgumentError, "First argument must be an empty array, address, or array of addresses."
  end

  @mem_cache_options = options.dup
  # The value "compress: false" prevents duplicate compression within Dalli.
  @mem_cache_options[:compress] = false
  (OVERRIDDEN_OPTIONS - %i(compress)).each { |name| @mem_cache_options.delete(name) }
  @data = self.class.build_mem_cache(*(addresses + [@mem_cache_options]))
end

Class Attribute Details

.supports_cache_versioning? ⇒ `Boolean` (readonly)

Advertise cache versioning support.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 38


def self.supports_cache_versioning?
  true
end

Class Method Details

.build_mem_cache(*addresses)

This method is for internal use only.

Creates a new Dalli::Client instance with specified addresses and options. If no addresses are provided, we give nil to Dalli::Client, so it uses its fallbacks:

ENV (if defined)

“127.0.0.1:11211” (otherwise)

ActiveSupport::Cache::MemCacheStore.build_mem_cache

# => #<Dalli::Client:0x007f98a47d2028 @servers=["127.0.0.1:11211"], @options={}, @ring=nil>

ActiveSupport::Cache::MemCacheStore.build_mem_cache(‘localhost:10290’)

# => #<Dalli::Client:0x007f98a47b3a60 @servers=["localhost:10290"], @options={}, @ring=nil>

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 56


def self.build_mem_cache(*addresses) # :nodoc:
  addresses = addresses.flatten
  options = addresses.extract_options!
  addresses = nil if addresses.compact.empty?
  pool_options = retrieve_pool_options(options)

  if pool_options
    ConnectionPool.new(pool_options) { Dalli::Client.new(addresses, options.merge(threadsafe: false)) }
  else
    Dalli::Client.new(addresses, options)
  end
end

Instance Method Details

#clear(options = nil)

Clear the entire cache on all memcached servers. This method should be used with care when shared cache is being used.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 171


def clear(options = nil)
  rescue_error_with(nil) { @data.with { |c| c.flush_all } }
end

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

Decrement a cached integer value using the memcached decr atomic operator. Returns the updated value.

If the key is unset or has expired, it will be set to 0. Memcached does not support negative counters.

cache.decrement("foo") # => 0

To set a specific value, call #write passing raw: true:

cache.write("baz", 5, raw: true)
cache.decrement("baz") # => 4

Decrementing a non-numeric value, or a value written without raw: true, will fail and return nil.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 158


def decrement(name, amount = 1, options = nil)
  options = merged_options(options)
  key = normalize_key(name, options)

  instrument(:decrement, key, amount: amount) do
    rescue_error_with nil do
      @data.with { |c| c.decr(key, amount, options[:expires_in], 0) }
    end
  end
end

#delete_entry(key, **options) (private)

Delete an entry from the cache.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 238


def delete_entry(key, **options)
  rescue_error_with(false) { @data.with { |c| c.delete(key) } }
end

#deserialize_entry(payload, raw: false) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 269


def deserialize_entry(payload, raw: false, **)
  if payload && raw
    Entry.new(payload)
  else
    super(payload)
  end
end

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

Increment a cached integer value using the memcached incr atomic operator. Returns the updated value.

If the key is unset or has expired, it will be set to amount:

cache.increment("foo") # => 1
cache.increment("bar", 100) # => 100

To set a specific value, call #write passing raw: true:

cache.write("baz", 5, raw: true)
cache.increment("baz") # => 6

Incrementing a non-numeric value, or a value written without raw: true, will fail and return nil.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 132


def increment(name, amount = 1, options = nil)
  options = merged_options(options)
  key = normalize_key(name, options)

  instrument(:increment, key, amount: amount) do
    rescue_error_with nil do
      @data.with { |c| c.incr(key, amount, options[:expires_in], amount) }
    end
  end
end

#inspect

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 96


def inspect
  instance = @data || @mem_cache_options
  "#<#{self.class} options=#{options.inspect} mem_cache=#{instance.inspect}>"
end

#normalize_key(key, options) (private)

Memcache keys are binaries. So we need to force their encoding to binary before applying the regular expression to ensure we are escaping all characters properly.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 253


def normalize_key(key, options)
  key = super
  if key
    key = key.dup.force_encoding(Encoding::ASCII_8BIT)
    key = key.gsub(ESCAPE_KEY_CHARS) { |match| "%#{match.getbyte(0).to_s(16).upcase}" }

    if key.size > KEY_MAX_SIZE
      key_separator = ":hash:"
      key_hash = ActiveSupport::Digest.hexdigest(key)
      key_trim_size = KEY_MAX_SIZE - key_separator.size - key_hash.size
      key = "#{key[0, key_trim_size]}#{key_separator}#{key_hash}"
    end
  end
  key
end

#read_entry(key, **options) (private)

Read an entry from the cache.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 182


def read_entry(key, **options)
  deserialize_entry(read_serialized_entry(key, **options), **options)
end

#read_multi_entries(names, **options) (private)

Reads multiple entries from the cache implementation.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 212


def read_multi_entries(names, **options)
  keys_to_names = names.index_by { |name| normalize_key(name, options) }

  raw_values = begin
    @data.with { |c| c.get_multi(keys_to_names.keys) }
  rescue Dalli::UnmarshalError
    {}
  end

  values = {}

  raw_values.each do |key, value|
    entry = deserialize_entry(value, raw: options[:raw])

    unless entry.nil? || entry.expired? || entry.mismatched?(normalize_version(keys_to_names[key], options))
      begin
        values[keys_to_names[key]] = entry.value
      rescue DeserializationError
      end
    end
  end

  values
end

#read_serialized_entry(key, **options) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 186


def read_serialized_entry(key, **options)
  rescue_error_with(nil) do
    @data.with { |c| c.get(key, options) }
  end
end

#rescue_error_with(fallback) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 277


def rescue_error_with(fallback)
  yield
rescue Dalli::DalliError => error
  logger.error("DalliError (#{error}): #{error.message}") if logger
  ActiveSupport.error_reporter&.report(
    error,
    severity: :warning,
    source: "mem_cache_store.active_support",
  )
  fallback
end

#serialize_entry(entry, raw: false, **options) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 242


def serialize_entry(entry, raw: false, **options)
  if raw
    entry.value.to_s
  else
    super(entry, raw: raw, **options)
  end
end

#stats

Get the statistics from the memcached servers.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 176


def stats
  @data.with { |c| c.stats }
end

#write(name, value, options = nil)

Behaves the same as Store#write, but supports additional options specific to memcached.

Additional Options

raw: true - Sends the value directly to the server as raw bytes. The value must be a string or number. You can use memcached direct operations like #increment and #decrement only on raw values.
unless_exist: true - Prevents overwriting an existing cache entry.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 102


rdoc_method :method: write

#write_entry(key, entry, **options) (private)

Write an entry to the cache.

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 193


def write_entry(key, entry, **options)
  write_serialized_entry(key, serialize_entry(entry, **options), **options)
end

#write_serialized_entry(key, payload, **options) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 197


def write_serialized_entry(key, payload, **options)
  method = options[:unless_exist] ? :add : :set
  expires_in = options[:expires_in].to_i
  if options[:race_condition_ttl] && expires_in > 0 && !options[:raw]
    # Set the memcache expire a few minutes in the future to support race condition ttls on read
    expires_in += 5.minutes
  end
  rescue_error_with nil do
    # Don't pass compress option to Dalli since we are already dealing with compression.
    options.delete(:compress)
    @data.with { |c| !!c.send(method, key, payload, expires_in, **options) }
  end
end

Class: ActiveSupport::Cache::MemCacheStore

Overview

Memcached Cache Store

Constant Summary

Store - Inherited

Class Attribute Summary

Store - Inherited

Class Method Summary

Store - Inherited

Instance Attribute Summary

Store - Inherited

Instance Method Summary

Strategy::LocalCache - Included

Store - Inherited

Constructor Details

.new(*addresses) ⇒ MemCacheStore

Class Attribute Details

.supports_cache_versioning? ⇒ Boolean (readonly)

Class Method Details

.build_mem_cache(*addresses)

Instance Method Details

#clear(options = nil)

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

#delete_entry(key, **options) (private)

#deserialize_entry(payload, raw: false) (private)

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

#inspect

#normalize_key(key, options) (private)

#read_entry(key, **options) (private)

#read_multi_entries(names, **options) (private)

#read_serialized_entry(key, **options) (private)

#rescue_error_with(fallback) (private)

#serialize_entry(entry, raw: false, **options) (private)

#stats

#write(name, value, options = nil)

Additional Options

#write_entry(key, entry, **options) (private)

#write_serialized_entry(key, payload, **options) (private)

`Store` - Inherited

`Store` - Inherited

`Store` - Inherited

`Store` - Inherited

`Strategy::LocalCache` - Included

`Store` - Inherited

.new(*addresses) ⇒ `MemCacheStore`

.supports_cache_versioning? ⇒ `Boolean` (readonly)