Class: RingCache

Inherits:
Object
  • Object
show all
Defined in:
lib/ring_cache.rb,
lib/ring_cache/version.rb

Defined Under Namespace

Classes: KeyNotFoundError

Constant Summary collapse

VERSION = 
'1.1'

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ RingCache

Returns a new instance of RingCache.



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# File 'lib/ring_cache.rb', line 8

def initialize(options = {})
  @duplicate_on_store = options.fetch(:duplicate_on_store, false)
  @duplicate_on_retrieve = options.fetch(:duplicate_on_retrieve, false)

  execute_on_retrieve = options.fetch(:execute_on_retrieve, [])
  @execute_on_retrieve = execute_on_retrieve.kind_of?(Array) ? execute_on_retrieve : [execute_on_retrieve]

  @capacity = options.fetch(:capacity, nil)
  @target_hit_rate = options.fetch(:target_hit_rate, nil)
  unless @target_hit_rate.nil? or (@target_hit_rate > 0.0 and @target_hit_rate < 1.0)
    raise ArgumentError, 'Invalid target_hit_rate'
  end

  reset
end

Instance Attribute Details

#capacity ⇒ Object (readonly)

Returns the value of attribute capacity.



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# File 'lib/ring_cache.rb', line 6

def capacity
  @capacity
end

#target_hit_rate ⇒ Object (readonly)

Returns the value of attribute target_hit_rate.



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# File 'lib/ring_cache.rb', line 6

def target_hit_rate
  @target_hit_rate
end

Instance Method Details

#evict(key) ⇒ Object 



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# File 'lib/ring_cache.rb', line 24

def evict(key)
  if @cache.has_key?(key)
    @access_time_index.delete([@cache[key][:last_accessed_at], key])
    @cache.delete(key)
    true
  else
    false
  end
end

#fetch(key, options = {}, &block) ⇒ Object 



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# File 'lib/ring_cache.rb', line 34

def fetch(key, options = {}, &block)
  cache_nil = options.fetch(:cache_nil, true)

  unless (data = read(key))
    data = catch(:dont_cache) do
      data_to_cache = block.call
      write(key, data_to_cache) unless data_to_cache.nil? and !cache_nil
      data_to_cache
    end
  end
  data
end

#has_key?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ring_cache.rb', line 47

def has_key?(key)
  @cache.has_key?(key)
end

#hit_rate ⇒ Object 



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# File 'lib/ring_cache.rb', line 51

def hit_rate
  (@access_count > 0) ? (@hit_count / @access_count.to_f) : 0.0
end

#last_access(key) ⇒ Object 



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# File 'lib/ring_cache.rb', line 55

def last_access(key)
  has_key?(key) ? @cache[key][:last_accessed_at] : nil
end

#read(key) ⇒ Object 



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# File 'lib/ring_cache.rb', line 92

def read(key)
  read!(key)
rescue KeyNotFoundError
  return nil
end

#read!(key) ⇒ Object 



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# File 'lib/ring_cache.rb', line 59

def read!(key)
  @access_count += 1

  if @cache.has_key?(key)
    access_time = Time.now
    @access_time_index.delete([@cache[key][:last_accessed_at], key])
    @access_time_index << [access_time, key]
    @cache[key][:last_accessed_at] = access_time

    @hit_count += 1

    data = @cache[key][:data]
    data = data.dup if @duplicate_on_retrieve and !data.nil?

    unless @execute_on_retrieve.empty? or data.nil?
      @execute_on_retrieve.each do |method|
        method = method.to_sym
        if data.respond_to?(method)
          data.send(method)
        elsif data.kind_of?(Enumerable) and data.all? { |d| d.respond_to?(method) }
          data.each { |d| d.send(method) }
        else
          raise RuntimeError, "Retrieved data does not respond to #{method.inspect}"
        end
      end
    end

    data
  else
    fail KeyNotFoundError, "Cache does not have content indexed by #{key}"
  end
end

#reset ⇒ Object 



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# File 'lib/ring_cache.rb', line 98

def reset
  @cache = {}
  @access_time_index = SortedSet.new
  @access_count = 0
  @hit_count = 0
  true
end

#size ⇒ Object 



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# File 'lib/ring_cache.rb', line 106

def size
  @cache.size
end

#write(key, data) ⇒ Object 



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# File 'lib/ring_cache.rb', line 110

def write(key, data)
  unless evict(key)
    evict_oldest if must_evict?
  end
  data = data.dup if @duplicate_on_store and !data.nil?
  access_time = Time.now
  @cache[key] = { last_accessed_at: access_time, data: data }
  @access_time_index << [access_time, key]
  true
end