aboutsummaryrefslogtreecommitdiffstats
path: root/activesupport/lib/active_support/cache.rb
blob: 7213b24f2d003ac29e79fd5771a1f8eb4b99aa86 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
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
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
require 'benchmark'
require 'active_support/core_ext/array/wrap'
require 'active_support/core_ext/benchmark'
require 'active_support/core_ext/exception'
require 'active_support/core_ext/class/attribute_accessors'
require 'active_support/core_ext/object/to_param'
require 'active_support/core_ext/string/inflections'

module ActiveSupport
  # See ActiveSupport::Cache::Store for documentation.
  module Cache
    autoload :FileStore, 'active_support/cache/file_store'
    autoload :MemoryStore, 'active_support/cache/memory_store'
    autoload :SynchronizedMemoryStore, 'active_support/cache/synchronized_memory_store'
    autoload :MemCacheStore, 'active_support/cache/mem_cache_store'
    autoload :CompressedMemCacheStore, 'active_support/cache/compressed_mem_cache_store'

    module Strategy
      autoload :LocalCache, 'active_support/cache/strategy/local_cache'
    end

    # Creates a new CacheStore object according to the given options.
    #
    # If no arguments are passed to this method, then a new
    # ActiveSupport::Cache::MemoryStore object will be returned.
    #
    # If you pass a Symbol as the first argument, then a corresponding cache
    # store class under the ActiveSupport::Cache namespace will be created.
    # For example:
    #
    #   ActiveSupport::Cache.lookup_store(:memory_store)
    #   # => returns a new ActiveSupport::Cache::MemoryStore object
    #
    #   ActiveSupport::Cache.lookup_store(:mem_cache_store)
    #   # => returns a new ActiveSupport::Cache::MemCacheStore object
    #
    # Any additional arguments will be passed to the corresponding cache store
    # class's constructor:
    #
    #   ActiveSupport::Cache.lookup_store(:file_store, "/tmp/cache")
    #   # => same as: ActiveSupport::Cache::FileStore.new("/tmp/cache")
    #
    # If the first argument is not a Symbol, then it will simply be returned:
    #
    #   ActiveSupport::Cache.lookup_store(MyOwnCacheStore.new)
    #   # => returns MyOwnCacheStore.new
    def self.lookup_store(*store_option)
      store, *parameters = *Array.wrap(store_option).flatten

      case store
      when Symbol
        store_class_name = store.to_s.camelize
        store_class = ActiveSupport::Cache.const_get(store_class_name)
        store_class.new(*parameters)
      when nil
        ActiveSupport::Cache::MemoryStore.new
      else
        store
      end
    end

    RAILS_CACHE_ID   = ENV["RAILS_CACHE_ID"]
    RAILS_APP_VERION = ENV["RAILS_APP_VERION"]
    EXPANDED_CACHE   = RAILS_CACHE_ID || RAILS_APP_VERION

    def self.expand_cache_key(key, namespace = nil)
      expanded_cache_key = namespace ? "#{namespace}/" : ""

      if EXPANDED_CACHE
        expanded_cache_key << "#{RAILS_CACHE_ID || RAILS_APP_VERION}/"
      end

      expanded_cache_key <<
        if key.respond_to?(:cache_key)
          key.cache_key
        elsif key.is_a?(Array)
          if key.size > 1
            key.collect { |element| expand_cache_key(element) }.to_param
          else
            key.first.to_param
          end
        elsif key
          key.to_param
        end.to_s

      expanded_cache_key
    end

    # An abstract cache store class. There are multiple cache store
    # implementations, each having its own additional features. See the classes
    # under the ActiveSupport::Cache module, e.g.
    # ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most
    # popular cache store for large production websites.
    #
    # ActiveSupport::Cache::Store is meant for caching strings. Some cache
    # store implementations, like MemoryStore, are able to cache arbitrary
    # Ruby objects, but don't count on every cache store to be able to do that.
    #
    #   cache = ActiveSupport::Cache::MemoryStore.new
    #
    #   cache.read("city")   # => nil
    #   cache.write("city", "Duckburgh")
    #   cache.read("city")   # => "Duckburgh"
    class Store
      cattr_accessor :logger, :instance_writter => false

      attr_reader :silence
      alias :silence? :silence

      def silence!
        @silence = true
        self
      end

      def mute
        previous_silence, @silence = defined?(@silence) && @silence, true
        yield
      ensure
        @silence = previous_silence
      end

      # Set to true if cache stores should be instrumented. By default is false.
      def self.instrument=(boolean)
        Thread.current[:instrument_cache_store] = boolean
      end

      def self.instrument
        Thread.current[:instrument_cache_store] || false
      end

      # Fetches data from the cache, using the given key. If there is data in
      # the cache with the given key, then that data is returned.
      #
      # If there is no such data in the cache (a cache miss occurred), then
      # then nil will be returned. However, if a block has been passed, then
      # that block will be run in the event of a cache miss. The return value
      # of the block will be written to the cache under the given cache key,
      # and that return value will be returned.
      #
      #   cache.write("today", "Monday")
      #   cache.fetch("today")  # => "Monday"
      #
      #   cache.fetch("city")   # => nil
      #   cache.fetch("city") do
      #     "Duckburgh"
      #   end
      #   cache.fetch("city")   # => "Duckburgh"
      #
      # You may also specify additional options via the +options+ argument.
      # Setting <tt>:force => true</tt> will force a cache miss:
      #
      #   cache.write("today", "Monday")
      #   cache.fetch("today", :force => true)  # => nil
      #
      # Other options will be handled by the specific cache store implementation.
      # Internally, #fetch calls #read, and calls #write on a cache miss.
      # +options+ will be passed to the #read and #write calls.
      #
      # For example, MemCacheStore's #write method supports the +:expires_in+
      # option, which tells the memcached server to automatically expire the
      # cache item after a certain period. This options is also supported by
      # FileStore's #read method. We can use this option with #fetch too:
      #
      #   cache = ActiveSupport::Cache::MemCacheStore.new
      #   cache.fetch("foo", :force => true, :expires_in => 5.seconds) do
      #     "bar"
      #   end
      #   cache.fetch("foo")  # => "bar"
      #   sleep(6)
      #   cache.fetch("foo")  # => nil
      def fetch(key, options = {}, &block)
        if !options[:force] && value = read(key, options)
          value
        elsif block_given?
          result = instrument(:generate, key, options, &block)
          write(key, result, options)
          result
        end
      end

      # Fetches data from the cache, using the given key. If there is data in
      # the cache with the given key, then that data is returned. Otherwise,
      # nil is returned.
      #
      # You may also specify additional options via the +options+ argument.
      # The specific cache store implementation will decide what to do with
      # +options+.
      #
      # For example, FileStore supports the +:expires_in+ option, which
      # makes the method return nil for cache items older than the specified
      # period.
      def read(key, options = nil, &block)
        instrument(:read, key, options, &block)
      end

      # Writes the given value to the cache, with the given key.
      #
      # You may also specify additional options via the +options+ argument.
      # The specific cache store implementation will decide what to do with
      # +options+.
      #
      # For example, MemCacheStore supports the +:expires_in+ option, which
      # tells the memcached server to automatically expire the cache item after
      # a certain period:
      #
      #   cache = ActiveSupport::Cache::MemCacheStore.new
      #   cache.write("foo", "bar", :expires_in => 5.seconds)
      #   cache.read("foo")  # => "bar"
      #   sleep(6)
      #   cache.read("foo")  # => nil
      def write(key, value, options = nil, &block)
        instrument(:write, key, options, &block)
      end

      def delete(key, options = nil, &block)
        instrument(:delete, key, options, &block)
      end

      def delete_matched(matcher, options = nil, &block)
        instrument(:delete_matched, matcher.inspect, options, &block)
      end

      def exist?(key, options = nil, &block)
        instrument(:exist?, key, options, &block)
      end

      def increment(key, amount = 1)
        if num = read(key)
          write(key, num + amount)
        else
          nil
        end
      end

      def decrement(key, amount = 1)
        if num = read(key)
          write(key, num - amount)
        else
          nil
        end
      end

      private
        def expires_in(options)
          expires_in = options && options[:expires_in]
          raise ":expires_in must be a number" if expires_in && !expires_in.is_a?(Numeric)
          expires_in || 0
        end

        def instrument(operation, key, options)
          log(operation, key, options)

          if self.class.instrument
            payload = { :key => key }
            payload.merge!(options) if options.is_a?(Hash)
            ActiveSupport::Notifications.instrument("active_support.cache_#{operation}", payload){ yield }
          else
            yield
          end
        end

        def log(operation, key, options)
          return unless logger && !silence?
          logger.debug("Cache #{operation}: #{key}#{options ? " (#{options.inspect})" : ""}")
        end
    end
  end
end