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Memory Cache Store

A cache store implementation which stores everything into memory in the same process. If you’re running multiple Ruby on Rails server processes (which is the case if you’re using Phusion Passenger or puma clustered mode), then this means that Rails server process instances won’t be able to share cache data with each other and this may not be the most appropriate cache in that scenario.

This cache has a bounded size specified by the :size options to the initializer (default is 32Mb). When the cache exceeds the allotted size, a cleanup will occur which tries to prune the cache down to three quarters of the maximum size by removing the least recently used entries.

Unlike other Cache store implementations, MemoryStore does not compress values by default. MemoryStore does not benefit from compression as much as other Store implementations, as it does not send data over a network. However, when compression is enabled, it still pays the full cost of compression in terms of cpu use.

MemoryStore is thread-safe.

Methods
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Constants

PER_ENTRY_OVERHEAD = 240
 

Class Public methods

new(options = nil)

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 73
def initialize(options = nil)
  options ||= {}
  options[:coder] = DupCoder unless options.key?(:coder) || options.key?(:serializer)
  # Disable compression by default.
  options[:compress] ||= false
  super(options)
  @data = {}
  @max_size = options[:size] || 32.megabytes
  @max_prune_time = options[:max_prune_time] || 2
  @cache_size = 0
  @monitor = Monitor.new
  @pruning = false
end

supports_cache_versioning?()

Advertise cache versioning support.

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 88
def self.supports_cache_versioning?
  true
end

Instance Public methods

cleanup(options = nil)

Preemptively iterates through all stored keys and removes the ones which have expired.

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 101
def cleanup(options = nil)
  options = merged_options(options)
  _instrument(:cleanup, size: @data.size) do
    keys = synchronize { @data.keys }
    keys.each do |key|
      entry = @data[key]
      delete_entry(key, **options) if entry && entry.expired?
    end
  end
end

clear(options = nil)

Delete all data stored in a given cache store.

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 93
def clear(options = nil)
  synchronize do
    @data.clear
    @cache_size = 0
  end
end

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

Decrement a cached integer value. Returns the updated value.

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

cache.decrement("foo") # => -1

To set a specific value, call write:

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

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 164
def decrement(name, amount = 1, options = nil)
  modify_value(name, -amount, options)
end

delete_matched(matcher, options = nil)

Deletes cache entries if the cache key matches a given pattern.

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 169
def delete_matched(matcher, options = nil)
  options = merged_options(options)
  matcher = key_matcher(matcher, options)

  instrument(:delete_matched, matcher.inspect) do
    keys = synchronize { @data.keys }
    keys.each do |key|
      delete_entry(key, **options) if key.match(matcher)
    end
  end
end

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

Increment a cached integer value. Returns the updated value.

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

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

To set a specific value, call write:

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

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 149
def increment(name, amount = 1, options = nil)
  modify_value(name, amount, options)
end

prune(target_size, max_time = nil)

To ensure entries fit within the specified memory prune the cache by removing the least recently accessed entries.

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 114
def prune(target_size, max_time = nil)
  return if pruning?
  @pruning = true
  begin
    start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    cleanup
    instrument(:prune, target_size, from: @cache_size) do
      keys = synchronize { @data.keys }
      keys.each do |key|
        delete_entry(key, **options)
        return if @cache_size <= target_size || (max_time && Process.clock_gettime(Process::CLOCK_MONOTONIC) - start_time > max_time)
      end
    end
  ensure
    @pruning = false
  end
end

pruning?()

Returns true if the cache is currently being pruned.

Source: show | on GitHub 

# File activesupport/lib/active_support/cache/memory_store.rb, line 133
def pruning?
  @pruning
end