Contents

# frozen_string_literal: true

module SupportTableCache
  # An optimized cache implementation that can be used when all records can easily fit
  # in memory and are never changed. It is intended for use with small, static support
  # tables only.
  #
  # This cache will not store nil values. This is to prevent the cache from filling up with
  # cache misses because there is no purging mechanism.
  class MemoryCache
    def initialize
      @cache = {}
      @mutex = Mutex.new
    end

    def fetch(key, expires_in: nil)
      serialized_value, expire_at = @cache[key]
      if serialized_value.nil? || (expire_at && expire_at < Process.clock_gettime(Process::CLOCK_MONOTONIC))
        value = yield if block_given?
        return nil if value.nil?
        write(key, value, expires_in: expires_in)
        serialized_value = Marshal.dump(value)
      end
      Marshal.load(serialized_value)
    end

    def read(key)
      fetch(key)
    end

    def write(key, value, expires_in: nil)
      return if value.nil?

      if expires_in
        expire_at = Process.clock_gettime(Process::CLOCK_MONOTONIC) + expires_in
      end

      serialized_value = Marshal.dump(value)

      @mutex.synchronize do
        @cache[key] = [serialized_value, expire_at]
      end
    end

    def delete(key)
      @cache.delete(key)
    end

    def clear
      @cache.clear
    end
  end
end

Version data entries

4 entries across 4 versions & 1 rubygems

Version	Path
support_table_cache-1.1.3	lib/support_table_cache/memory_cache.rb
support_table_cache-1.1.2	lib/support_table_cache/memory_cache.rb
support_table_cache-1.1.1	lib/support_table_cache/memory_cache.rb
support_table_cache-1.1.0	lib/support_table_cache/memory_cache.rb