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

Constants

PER_ENTRY_OVERHEAD = 240

Class Public methods

new(options = nil)

📝 Source code 
# 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
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supports_cache_versioning?()

Advertise cache versioning support.

📝 Source code 
# File activesupport/lib/active_support/cache/memory_store.rb, line 88
      def self.supports_cache_versioning?
        true
      end
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Instance Public methods

cleanup(options = nil)

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

📝 Source code 
# 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
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clear(options = nil)

Delete all data stored in a given cache store.

📝 Source code 
# File activesupport/lib/active_support/cache/memory_store.rb, line 93
      def clear(options = nil)
        synchronize do
          @data.clear
          @cache_size = 0
        end
      end
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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 code 
# File activesupport/lib/active_support/cache/memory_store.rb, line 164
      def decrement(name, amount = 1, options = nil)
        modify_value(name, -amount, options)
      end
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delete_matched(matcher, options = nil)

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

📝 Source code 
# File activesupport/lib/active_support/cache/memory_store.rb, line 169
      def delete_matched(matcher, options = nil)
        options = merged_options(options)
        instrument(:delete_matched, matcher.inspect) do
          matcher = key_matcher(matcher, options)
          keys = synchronize { @data.keys }
          keys.each do |key|
            delete_entry(key, **options) if key.match(matcher)
          end
        end
      end
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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 code 
# File activesupport/lib/active_support/cache/memory_store.rb, line 149
      def increment(name, amount = 1, options = nil)
        modify_value(name, amount, options)
      end
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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 code 
# 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
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pruning?()

Returns true if the cache is currently being pruned.

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