Refactor Cache::Entry compression handling

Rather than immediately compressing the cache value
in the constructor, this operation is delayed until
we need to serialize the entry.

activesupport/lib/active_support/cache.rb

@@ -24,6 +24,8 @@ module ActiveSupport
     # implementations may support additional options.
     UNIVERSAL_OPTIONS = [:namespace, :compress, :compress_threshold, :expires_in, :expire_in, :expired_in, :race_condition_ttl, :coder, :skip_nil]
 
+    DEFAULT_COMPRESS_LIMIT = 1.kilobyte
+
     # Mapping of canonical option names to aliases that a store will recognize.
     OPTION_ALIASES = {
       expires_in: [:expire_in, :expired_in]
@@ -169,7 +171,23 @@ module ActiveSupport
     # threshold is configurable with the <tt>:compress_threshold</tt> option,
     # specified in bytes.
     class Store
-      DEFAULT_CODER = Marshal
+      module MarshalCoder # :nodoc:
+        extend self
+
+        def dump(entry)
+          Marshal.dump(entry)
+        end
+
+        def dump_compressed(entry, threshold)
+          Marshal.dump(entry.compressed(threshold))
+        end
+
+        def load(payload)
+          Marshal.load(payload)
+        end
+      end
+
+      DEFAULT_CODER = MarshalCoder
 
       cattr_accessor :logger, instance_writer: true
 
@@ -198,7 +216,11 @@ module ActiveSupport
       # namespace for the cache.
       def initialize(options = nil)
         @options = options ? normalize_options(options) : {}
+        @options[:compress] = true unless @options.key?(:compress)
+        @options[:compress_threshold] = DEFAULT_COMPRESS_LIMIT unless @options.key?(:compress_threshold)
+
         @coder = @options.delete(:coder) { self.class::DEFAULT_CODER } || NullCoder
+        @coder_supports_compression = @coder.respond_to?(:dump_compressed)
       end
 
       # Silences the logger.
@@ -609,9 +631,14 @@ module ActiveSupport
           raise NotImplementedError.new
         end
 
-        def serialize_entry(entry)
+        def serialize_entry(entry, **options)
+          options = merged_options(options)
+          if @coder_supports_compression && options[:compress]
+            @coder.dump_compressed(entry, options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT)
+          else
             @coder.dump(entry)
           end
+        end
 
         def deserialize_entry(payload)
           payload.nil? ? nil : @coder.load(payload)
@@ -789,14 +816,18 @@ module ActiveSupport
     end
 
     module NullCoder # :nodoc:
-      class << self
-        def load(payload)
-          payload
-        end
+      extend self
 
       def dump(entry)
         entry
       end
+
+      def dump_compressed(entry, threshold)
+        entry.compressed(threshold)
+      end
+
+      def load(payload)
+        payload
       end
     end
 
@@ -810,17 +841,15 @@ module ActiveSupport
     class Entry # :nodoc:
       attr_reader :version
 
-      DEFAULT_COMPRESS_LIMIT = 1.kilobyte
-
       # Creates a new cache entry for the specified value. Options supported are
-      # +:compress+, +:compress_threshold+, +:version+, +:expires_at+ and +:expires_in+.
-      def initialize(value, compress: true, compress_threshold: DEFAULT_COMPRESS_LIMIT, version: nil, expires_in: nil, expires_at: nil, **)
+      # +:compressed+, +:version+, +:expires_at+ and +:expires_in+.
+      def initialize(value, compressed: false, version: nil, expires_in: nil, expires_at: nil, **)
         @value      = value
         @version    = version
         @created_at = 0.0
         @expires_in = expires_at&.to_f || expires_in && (expires_in.to_f + Time.now.to_f)
 
-        compress!(compress_threshold) if compress
+        @compressed = true if compressed
       end
 
       def value
@@ -866,6 +895,30 @@ module ActiveSupport
         defined?(@compressed)
       end
 
+      def compressed(compress_threshold)
+        return self if compressed?
+
+        case @value
+        when nil, true, false, Numeric
+          uncompressed_size = 0
+        when String
+          uncompressed_size = @value.bytesize
+        else
+          serialized = Marshal.dump(@value)
+          uncompressed_size = serialized.bytesize
+        end
+
+        if uncompressed_size >= compress_threshold
+          serialized ||= Marshal.dump(@value)
+          compressed = Zlib::Deflate.deflate(serialized)
+
+          if compressed.bytesize < uncompressed_size
+            return Entry.new(compressed, compressed: true, expires_at: expires_at, version: version)
+          end
+        end
+        self
+      end
+
       def local?
         false
       end
@@ -883,28 +936,6 @@ module ActiveSupport
       end
 
       private
-        def compress!(compress_threshold)
-          case @value
-          when nil, true, false, Numeric
-            uncompressed_size = 0
-          when String
-            uncompressed_size = @value.bytesize
-          else
-            serialized = Marshal.dump(@value)
-            uncompressed_size = serialized.bytesize
-          end
-
-          if uncompressed_size >= compress_threshold
-            serialized ||= Marshal.dump(@value)
-            compressed = Zlib::Deflate.deflate(serialized)
-
-            if compressed.bytesize < uncompressed_size
-              @value = compressed
-              @compressed = true
-            end
-          end
-        end
-
         def uncompress(value)
           Marshal.load(Zlib::Inflate.inflate(value))
         end

activesupport/lib/active_support/cache/file_store.rb

@@ -73,7 +73,7 @@ module ActiveSupport
       private
         def read_entry(key, **options)
           if File.exist?(key)
-            entry = File.open(key) { |f| deserialize_entry(f.read) }
+            entry = deserialize_entry(File.binread(key))
             entry if entry.is_a?(Cache::Entry)
           end
         rescue => e
@@ -84,7 +84,8 @@ module ActiveSupport
         def write_entry(key, entry, **options)
           return false if options[:unless_exist] && File.exist?(key)
           ensure_cache_path(File.dirname(key))
-          File.atomic_write(key, cache_path) { |f| f.write(serialize_entry(entry)) }
+          payload = serialize_entry(entry, **options)
+          File.atomic_write(key, cache_path) { |f| f.write(payload) }
           true
         end
 

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -148,7 +148,7 @@ module ActiveSupport
         # Write an entry to the cache.
         def write_entry(key, entry, **options)
           method = options[:unless_exist] ? :add : :set
-          value = options[:raw] ? entry.value.to_s : serialize_entry(entry)
+          value = options[:raw] ? entry.value.to_s : serialize_entry(entry, **options)
           expires_in = options[:expires_in].to_i
           if options[:race_condition_ttl] && expires_in > 0 && !options[:raw]
             # Set the memcache expire a few minutes in the future to support race condition ttls on read
@@ -198,7 +198,7 @@ module ActiveSupport
 
         def deserialize_entry(payload)
           entry = super
-          entry = Entry.new(entry, compress: false) if entry && !entry.is_a?(Entry)
+          entry = Entry.new(entry) if entry && !entry.is_a?(Entry)
           entry
         end
 

activesupport/lib/active_support/cache/memory_store.rb

@@ -25,18 +25,24 @@ module ActiveSupport
     # MemoryStore is thread-safe.
     class MemoryStore < Store
       module DupCoder # :nodoc:
-        class << self
+        extend self
+
+        def dump(entry)
+          entry.dup_value! unless entry.compressed?
+          entry
+        end
+
+        def dump_compressed(entry, threshold)
+          entry = entry.compressed(threshold)
+          entry.dup_value! unless entry.compressed?
+          entry
+        end
+
         def load(entry)
           entry = entry.dup
           entry.dup_value!
           entry
         end
-
-          def dump(entry)
-            entry.dup_value!
-            entry
-          end
-        end
       end
 
       DEFAULT_CODER = DupCoder
@@ -156,7 +162,7 @@ module ActiveSupport
         end
 
         def write_entry(key, entry, **options)
-          payload = serialize_entry(entry)
+          payload = serialize_entry(entry, **options)
           synchronize do
             return false if options[:unless_exist] && @data.key?(key)
 

activesupport/lib/active_support/cache/redis_cache_store.rb

@@ -388,7 +388,7 @@ module ActiveSupport
         #
         # Requires Redis 2.6.12+ for extended SET options.
         def write_entry(key, entry, unless_exist: false, raw: false, expires_in: nil, race_condition_ttl: nil, **options)
-          serialized_entry = serialize_entry(entry, raw: raw)
+          serialized_entry = serialize_entry(entry, raw: raw, **options)
 
           # If race condition TTL is in use, ensure that cache entries
           # stick around a bit longer after they would have expired
@@ -433,7 +433,7 @@ module ActiveSupport
           if entries.any?
             if mset_capable? && expires_in.nil?
               failsafe :write_multi_entries do
-                redis.with { |c| c.mapped_mset(serialize_entries(entries, raw: options[:raw])) }
+                redis.with { |c| c.mapped_mset(serialize_entries(entries, **options)) }
               end
             else
               super
@@ -458,23 +458,23 @@ module ActiveSupport
 
         def deserialize_entry(payload, raw:)
           if payload && raw
-            Entry.new(payload, compress: false)
+            Entry.new(payload)
           else
             super(payload)
           end
         end
 
-        def serialize_entry(entry, raw: false)
+        def serialize_entry(entry, raw: false, **options)
           if raw
             entry.value.to_s
           else
-            super(entry)
+            super(entry, raw: raw, **options)
           end
         end
 
-        def serialize_entries(entries, raw: false)
+        def serialize_entries(entries, **options)
           entries.transform_values do |entry|
-            serialize_entry entry, raw: raw
+            serialize_entry(entry, **options)
           end
         end
 

activesupport/test/cache/stores/mem_cache_store_test.rb

@@ -77,7 +77,7 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     cache = lookup_store(raw: true)
     cache.write("foo", 2)
 
-    assert_not_called_on_instance_of ActiveSupport::Cache::Entry, :compress! do
+    assert_not_called_on_instance_of ActiveSupport::Cache::Entry, :compressed do
       cache.read("foo")
     end
   end

activesupport/test/cache/stores/redis_cache_store_test.rb

@@ -329,7 +329,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
     test "does not compress values read with \"raw\" enabled" do
       @cache.write("foo", "bar", raw: true)
 
-      assert_not_called_on_instance_of ActiveSupport::Cache::Entry, :compress! do
+      assert_not_called_on_instance_of ActiveSupport::Cache::Entry, :compressed do
         @cache.read("foo", raw: true)
       end
     end