Class: RingCache

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

Constant Summary collapse

VERSION = 
'1.0'

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ RingCache

Returns a new instance of RingCache.



10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
 
# File 'lib/ring_cache.rb', line 10

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.



8
9
10
 
# File 'lib/ring_cache.rb', line 8

def capacity
  @capacity
end

#target_hit_rate ⇒ Object (readonly)

Returns the value of attribute target_hit_rate.



8
9
10
 
# File 'lib/ring_cache.rb', line 8

def target_hit_rate
  @target_hit_rate
end

Instance Method Details

#evict(key) ⇒ Object 



26
27
28
29
30
31
32
33
34
 
# File 'lib/ring_cache.rb', line 26

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, &block) ⇒ Object 



36
37
38
39
40
41
42
 
# File 'lib/ring_cache.rb', line 36

def fetch(key, &block)
  unless (data = read(key))
    data = block.call
    write(key, data)
  end
  data
end

#has_key?(key) ⇒ Boolean

Returns:

  • (Boolean) 


44
45
46
 
# File 'lib/ring_cache.rb', line 44

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

#hit_rate ⇒ Object 



48
49
50
 
# File 'lib/ring_cache.rb', line 48

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

#last_access(key) ⇒ Object 



52
53
54
 
# File 'lib/ring_cache.rb', line 52

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

#read(key) ⇒ Object 



56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
 
# File 'lib/ring_cache.rb', line 56

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
    nil
  end
end

#reset ⇒ Object 



89
90
91
92
93
94
95
 
# File 'lib/ring_cache.rb', line 89

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

#size ⇒ Object 



97
98
99
 
# File 'lib/ring_cache.rb', line 97

def size
  @cache.size
end

#write(key, data) ⇒ Object 



101
102
103
104
105
106
107
 
# File 'lib/ring_cache.rb', line 101

def write(key, data)
  evict_oldest if must_evict?
  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]
end