async_write_store.rb

require 'concurrent'

module ActiveSupport
  module Cache
    class AsyncWriteStore < SimpleDelegator
      def self.supports_cache_versioning?
        true
      end

      def initialize(klass_or_sym, *args)
        @store = build_store(klass_or_sym, args)
        @pool = Concurrent::ThreadPoolExecutor.new(
          min_threads: 5,
          max_threads: 5,
          max_queue: 100,
          fallback_policy: :discard
        )

        ensure_store_supports_cache_versioning!

        super(@store)
      end

      def ensure_store_supports_cache_versioning!
        return if @store.class.supports_cache_versioning?

        raise "#{@store.class.name} does not support cache versioning!"
      end

      def write(*args)
        @pool << proc { @store.write(*args) }
      end

      private

      def build_store(klass_or_sym, args)
        if klass_or_sym.is_a?(Symbol)
          ActiveSupport::Cache.lookup_store(klass_or_sym, *args)
        else
          klass_or_sym.new(*args)
        end
      end
    end
  end
end