[operation/fetch] AnyCache#fetch

lib/any_cache.rb

@@ -75,7 +75,8 @@ def build(driver = Drivers.build(config))
                  :expire,
                  :persist,
                  :clear,
-                 :exist?
+                 :exist?,
+                 :fetch
 
   # @return [AnyCache::Adapters::Basic]
   #

lib/any_cache/adapters/active_support_mem_cache_store.rb

@@ -143,5 +143,19 @@ def persist(key, **options)
     def exist?(key, **options)
       driver.exist?(key)
     end
+
+    # @param key [String]
+    # @option expires_in [Integer]
+    # @return [Object]
+    #
+    # @api private
+    # @since 0.2.0
+    def fetch(key, **options, &block)
+      force_rewrite = options.fetch(:force, false)
+      force_rewrite = force_rewrite.call if force_rewrite.respond_to?(:call)
+      expires_in    = options.fetch(:expires_in, NO_EXPIRATION_TTL)
+
+      driver.fetch(key, force: force_rewrite, expires_in: expires_in, &block)
+    end
   end
 end

lib/any_cache/adapters/active_support_naive_store.rb

@@ -128,6 +128,22 @@ def exist?(key, **options)
       lock.with_read_lock { super }
     end
 
+    # @param key [String]
+    # @option expires_in [Integer]
+    # @return [Object]
+    #
+    # @api private
+    # @since 0.2.0
+    def fetch(key, **options, &block)
+      lock.with_write_lock do
+        force_rewrite = options.fetch(:force, false)
+        force_rewrite = force_rewrite.call if force_rewrite.respond_to?(:call)
+        expires_in    = options.fetch(:expires_in, self.class::Operation::NO_EXPIRATION_TTL)
+
+        super(key, force: force_rewrite, expires_in: expires_in, &block)
+      end
+    end
+
     private
 
     # @return [Concurrent::ReentrantReadWriteLock]

lib/any_cache/adapters/active_support_redis_cache_store.rb

@@ -70,7 +70,7 @@ def write(key, value, **options)
     # @since 0.1.0
     def increment(key, amount = DEFAULT_INCR_DECR_AMOUNT, **options)
       expires_in = options.fetch(:expires_in, NO_EXPIRATION_TTL)
-      is_initial = !read(key) # TODO: rewrite with #exist?(key)
+      is_initial = exist?(key)
 
       if is_initial
         write(key, amount, expires_in: expires_in) && amount
@@ -90,7 +90,7 @@ def increment(key, amount = DEFAULT_INCR_DECR_AMOUNT, **options)
     # @since 0.1.0
     def decrement(key, amount = DEFAULT_INCR_DECR_AMOUNT, **options)
       expires_in = options.fetch(:expires_in, NO_EXPIRATION_TTL)
-      is_initial = !read(key) # TODO: rewrite with #exist?(key)
+      is_initial = exist?(key)
 
       if is_initial
         write(key, -amount, expires_in: expires_in) && -amount
@@ -133,5 +133,19 @@ def persist(key, **options)
     def exist?(key, **options)
       driver.exist?(key)
     end
+
+    # @param key [String]
+    # @option expires_in [Integer]
+    # @return [Object]
+    #
+    # @api private
+    # @since 0.2.0
+    def fetch(key, **options, &block)
+      force_rewrite = options.fetch(:force, false)
+      force_rewrite = force_rewrite.call if force_rewrite.respond_to?(:call)
+      expires_in    = options.fetch(:expires_in, NO_EXPIRATION_TTL)
+
+      driver.fetch(key, force: force_rewrite, expires_in: expires_in, &block)
+    end
   end
 end

lib/any_cache/adapters/basic.rb

@@ -124,5 +124,15 @@ def clear(**options)
     def exist?(key, **options)
       raise NotImplementedError
     end
+
+    # @param key [String]
+    # @param options [Hash]
+    # @return [Object]
+    #
+    # @api private
+    # @since 0.2.0
+    def fetch(key, **options, &block)
+      raise NotImplementedError
+    end
   end
 end

lib/any_cache/adapters/dalli.rb

@@ -144,7 +144,24 @@ def clear(**options)
     # @api private
     # @since 0.2.0
     def exist?(key, **options)
-      !get(key).nil? # NOTE: can conflict with :cache_nils Dalli::Client option
+      !get(key).nil? # NOTE: can conflict with :cache_nils Dalli::Client's config
+    end
+
+    # @param key [String]
+    # @option expires_in [Integer]
+    # @option force [Boolean]
+    # @return [Object]
+    #
+    # @api private
+    # @since 0.2.0
+    def fetch(key, **options)
+      force_rewrite = options.fetch(:force, false)
+      force_rewrite = force_rewrite.call if force_rewrite.respond_to?(:call)
+
+      # NOTE: can conflict with :cache_nils Dalli::Client's config
+      read(key).tap { |value| return value if value } unless force_rewrite
+
+      yield.tap { |value| write(key, value, **options) } if block_given?
     end
   end
 end

lib/any_cache/adapters/delegator.rb

@@ -19,7 +19,8 @@ def supported_driver?(driver)
         driver.respond_to?(:expire) &&
         driver.respond_to?(:persist) &&
         driver.respond_to?(:clear) &&
-        driver.respond_to?(:exist?)
+        driver.respond_to?(:exist?) &&
+        driver.respond_to?(:fetch)
       end
     end
 
@@ -33,6 +34,7 @@ def supported_driver?(driver)
                    :expire,
                    :persist,
                    :clear,
-                   :exist?
+                   :exist?,
+                   :fetch
   end
 end

lib/any_cache/adapters/redis.rb

@@ -89,7 +89,6 @@ def increment(key, amount = DEFAULT_INCR_DECR_AMOUNT, **options)
       expires_in = options.fetch(:expires_in, NO_EXPIRATION_TTL)
       new_amount = nil
 
-      # TODO: think about Redis#multi
       pipelined do
         new_amount = incrby(key, amount)
         expire(key, expires_in: expires_in) if expires_in
@@ -109,7 +108,6 @@ def decrement(key, amount = DEFAULT_INCR_DECR_AMOUNT, **options)
       expires_in = options.fetch(:expires_in, NO_EXPIRATION_TTL)
       new_amount = nil
 
-      # TODO: think about Redis#multi
       pipelined do
         new_amount = decrby(key, amount)
         expire(key, expires_in: expires_in) if expires_in
@@ -158,5 +156,21 @@ def clear(**options)
     def exist?(key, **options)
       exists(key)
     end
+
+    # @param key [String]
+    # @option expires_in [Integer]
+    # @return [Object]
+    #
+    # @api private
+    # @since 0.2.0
+    def fetch(key, **options)
+      force_rewrite = options.fetch(:force, false)
+      force_rewrite = force_rewrite.call if force_rewrite.respond_to?(:call)
+
+      # NOTE: think about #pipelined
+      read(key).tap { |value| return value if value } unless force_rewrite
+
+      yield.tap { |value| write(key, value, **options) } if block_given?
+    end
   end
 end

spec/features/clear_spec.rb

@@ -1,9 +1,7 @@
 # frozen_string_literal: true
 
 describe 'Operation: #clear' do
-  let(:cache_store) { build_cache_store }
-
-  after { cache_store.clear }
+  include_context 'cache store'
 
   it 'clears storage' do
     # NOTE: write random values

spec/features/custom_cache_clients_spec.rb

@@ -14,6 +14,7 @@ def expire(key, **); end
         def persist(key, **); end
         def clear(key, **); end
         def exist?(key, **); end
+        def fetch(key, **); end
         # rubocop:enable Layout/EmptyLineBetweenDefs
       end.new
     end
@@ -30,6 +31,7 @@ def expire; end
         def persist; end
         def clear; end
         def exist?; end
+        def fetch; end
       end.new
       # rubocop:enable Layout/EmptyLineBetweenDefs
     end
@@ -48,6 +50,7 @@ def exist?; end
       expire
       persist
       clear
+      fetch
       exist?
     ].each do |operation|
       specify "AnyCache instance delegates :#{operation} operation to the custom client" do
@@ -90,6 +93,7 @@ def exist?; end
         expire
         persist
         clear
+        fetch
         exist?
       ]
     end

spec/features/decrement_spec.rb

@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 describe 'Operation: #decrement' do
-  after { cache_store.clear }
+  include_context 'cache store'
 
-  let(:cache_store)     { build_cache_store }
   let(:expiration_time) { 8 } # NOTE: in seconds
   let(:entry)           { { key: SecureRandom.hex, value: 1 } }
 

spec/features/delete_spec.rb

@@ -1,9 +1,7 @@
 # frozen_string_literal: true
 
 describe 'Operation: #delete' do
-  after { cache_store.clear }
-
-  let(:cache_store) { build_cache_store }
+  include_context 'cache store'
 
   it 'removes entry from cache' do
     first_pair  = { key: SecureRandom.hex, value: SecureRandom.hex(4) }

spec/features/fetch_spec.rb

@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+describe 'Command: #fetch' do
+  include_context 'cache store'
+
+  let(:entry)      { { key: SecureRandom.hex, value: SecureRandom.hex(4) } }
+  let(:expires_in) { 5 } # NOTE: in seconds
+
+  specify 'fetching without expiration attribue creates a permanent entry' do
+    expect(cache_store.fetch(entry[:key])).to eq(nil)
+
+    result = cache_store.fetch(entry[:key]) { entry[:value] }
+
+    expect(result).to eq(entry[:value])
+    expect(cache_store.fetch(entry[:key])).to eq(entry[:value])
+
+    sleep(expires_in + 1)
+
+    expect(cache_store.fetch(entry[:key])).to eq(entry[:value])
+  end
+
+  specify 'fetching with expiration attribute creates a temporal entry' do
+    expect(cache_store.fetch(entry[:key])).to eq(nil)
+
+    result = cache_store.fetch(entry[:key], expires_in: expires_in) { entry[:value] }
+
+    expect(result).to eq(entry[:value])
+    expect(cache_store.fetch(entry[:key])).to eq(entry[:value])
+
+    sleep(expires_in + 1)
+
+    expect(cache_store.fetch(entry[:key])).to eq(nil)
+  end
+
+  specify 'fetching with :force option creates new entry' do
+    expect(cache_store.fetch(entry[:key])).to eq(nil)
+
+    # NOTE: initial permanent entry
+    entry_value = SecureRandom.hex(4)
+    result = cache_store.fetch(entry[:key], force: true) { entry_value }
+
+    expect(result).to eq(entry_value)
+    expect(cache_store.fetch(entry[:key])).to eq(entry_value)
+
+    # NOTE: new permanent value
+    entry_value = SecureRandom.hex(4)
+    result = cache_store.fetch(entry[:key], force: true) { entry_value }
+
+    expect(result).to eq(entry_value)
+    expect(cache_store.fetch(entry[:key])).to eq(entry_value)
+
+    # NOTE: new temporal entry
+    entry_value = SecureRandom.hex(4)
+    result = cache_store.fetch(entry[:key], expires_in: expires_in, force: true) do
+      entry_value
+    end
+
+    expect(result).to eq(entry_value)
+    expect(cache_store.fetch(entry[:key])).to eq(entry_value)
+    sleep(expires_in + 1) # NOTE: expire new temporal entry
+    expect(cache_store.fetch(entry[:key])).to eq(nil)
+
+    # NOTE: prepare new temporal entry
+    entry_value = SecureRandom.hex(4)
+    cache_store.write(entry[:key], entry[:value], expires_in: expires_in)
+
+    # NOTE: rewrite new temporal entry with permanent entry
+    result = cache_store.fetch(entry[:key], force: true) { entry_value }
+    expect(result).to eq(entry_value)
+    expect(cache_store.fetch(entry[:key])).to eq(entry_value)
+
+    sleep(expires_in + 1) # NOTE: try to expire rewritten entry
+
+    expect(cache_store.fetch(entry[:key])).to eq(entry_value)
+  end
+end

spec/features/increment_spec.rb

@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 describe 'Operation: #increment' do
-  after { cache_store.clear }
+  include_context 'cache store'
 
-  let(:cache_store)     { build_cache_store }
   let(:expiration_time) { 8 } # NOTE: in seconds
   let(:entry)           { { key: SecureRandom.hex, value: 1 } }
 

spec/features/persist_spec.rb

@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 describe 'Operation: #persist' do
-  after { cache_store.clear }
+  include_context 'cache store'
 
-  let(:cache_store) { build_cache_store }
   let(:first_entry)  { { key: SecureRandom.hex, value: SecureRandom.hex(4) } }
   let(:second_entry) { { key: SecureRandom.hex, value: SecureRandom.hex(4) } }
 

spec/features/read_spec.rb

@@ -1,9 +1,7 @@
 # frozen_string_literal: true
 
 describe 'Operation: #read' do
-  after { cache_store.clear }
-
-  let(:cache_store) { build_cache_store }
+  include_context 'cache store'
 
   context 'when the required entry exists' do
     let(:expiration_time) { 8 } # NOTE: in seconds

spec/features/write_spec.rb

@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 describe 'Operation: #write' do
-  after { cache_store.clear }
+  include_context 'cache store'
 
-  let(:cache_store)     { build_cache_store }
   let(:expiration_time) { 8 } # NOTE: in seconds
   let(:first_pair)      { { key: SecureRandom.hex, value: SecureRandom.hex(4) } }
   let(:second_pair)     { { key: SecureRandom.hex, value: SecureRandom.hex(4) } }

spec/spec_helper.rb

@@ -15,6 +15,7 @@
 require 'pry'
 
 require_relative 'support/spec_support'
+require_relative 'support/shared_contexts'
 
 RSpec.configure do |config|
   config.filter_run_when_matching :focus

spec/support/shared_contexts.rb

@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require_relative 'shared_contexts/cache_store'

spec/support/shared_contexts/cache_store.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+shared_context 'cache store' do
+  after { cache_store.clear }
+
+  let(:cache_store) { build_cache_store }
+end