aboutsummaryrefslogtreecommitdiffstats
path: root/activesupport/lib/active_support/cache/strategy/local_cache.rb
blob: db5f228a70609dc11e0fc4966f274a432439073a (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
require 'active_support/core_ext/object/duplicable'
require 'active_support/core_ext/string/inflections'

module ActiveSupport
  module Cache
    module Strategy
      # Caches that implement LocalCache will be backed by an in-memory cache for the
      # duration of a block. Repeated calls to the cache for the same key will hit the
      # in-memory cache for faster access.
      module LocalCache
        # Simple memory backed cache. This cache is not thread safe and is intended only
        # for serving as a temporary memory cache for a single thread.
        class LocalStore < Store
          def initialize
            super
            @data = {}
          end

          # Don't allow synchronizing since it isn't thread safe,
          def synchronize # :nodoc:
            yield
          end

          def clear(options = nil)
            @data.clear
          end

          def read_entry(key, options)
            @data[key]
          end

          def write_entry(key, value, options)
            @data[key] = value
            true
          end

          def delete_entry(key, options)
            !!@data.delete(key)
          end
        end

        # Use a local cache for the duration of block.
        def with_local_cache
          save_val = Thread.current[thread_local_key]
          begin
            Thread.current[thread_local_key] = LocalStore.new
            yield
          ensure
            Thread.current[thread_local_key] = save_val
          end
        end

        #--
        # This class wraps up local storage for middlewares. Only the middleware method should
        # construct them.
        class Middleware # :nodoc:
          attr_reader :name, :thread_local_key

          def initialize(name, thread_local_key)
            @name             = name
            @thread_local_key = thread_local_key
            @app              = nil
          end

          def new(app)
            @app = app
            self
          end

          def call(env)
            Thread.current[thread_local_key] = LocalStore.new
            @app.call(env)
          ensure
            Thread.current[thread_local_key] = nil
          end
        end

        # Middleware class can be inserted as a Rack handler to be local cache for the
        # duration of request.
        def middleware
          @middleware ||= Middleware.new(
            "ActiveSupport::Cache::Strategy::LocalCache",
            thread_local_key)
        end

        def clear(options = nil) # :nodoc:
          local_cache.clear(options) if local_cache
          super
        end

        def cleanup(options = nil) # :nodoc:
          local_cache.clear(options) if local_cache
          super
        end

        def increment(name, amount = 1, options = nil) # :nodoc:
          value = bypass_local_cache{super}
          if local_cache
            local_cache.mute do
              if value
                local_cache.write(name, value, options)
              else
                local_cache.delete(name, options)
              end
            end
          end
          value
        end

        def decrement(name, amount = 1, options = nil) # :nodoc:
          value = bypass_local_cache{super}
          if local_cache
            local_cache.mute do
              if value
                local_cache.write(name, value, options)
              else
                local_cache.delete(name, options)
              end
            end
          end
          value
        end

        protected
          def read_entry(key, options) # :nodoc:
            if local_cache
              entry = local_cache.read_entry(key, options)
              unless entry
                entry = super
                local_cache.write_entry(key, entry, options)
              end
              entry
            else
              super
            end
          end

          def write_entry(key, entry, options) # :nodoc:
            local_cache.write_entry(key, entry, options) if local_cache
            super
          end

          def delete_entry(key, options) # :nodoc:
            local_cache.delete_entry(key, options) if local_cache
            super
          end

        private
          def thread_local_key
            @thread_local_key ||= "#{self.class.name.underscore}_local_cache_#{object_id}".gsub(/[\/-]/, '_').to_sym
          end

          def local_cache
            Thread.current[thread_local_key]
          end

          def bypass_local_cache
            save_cache = Thread.current[thread_local_key]
            begin
              Thread.current[thread_local_key] = nil
              yield
            ensure
              Thread.current[thread_local_key] = save_cache
            end
          end
      end
    end
  end
end