From ed100166874fb4a542c5aaba933a4cca5ed72269 Mon Sep 17 00:00:00 2001
From: Jeremy Daer <jeremydaer@gmail.com>
Date: Mon, 13 Nov 2017 19:16:53 -0700
Subject: Cache: Enable compression by default for values > 1kB.

Compression has long been available, but opt-in and at a 16kB threshold.
It wasn't enabled by default due to CPU cost. Today it's cheap and
typical cache data is eminently compressible, such as HTML or JSON
fragments.

Compression dramatically reduces Memcached/Redis mem usage, which means
the same cache servers can store more data, which means higher hit
rates.

To disable compression, pass `compress: false` to the initializer.
---
 activesupport/lib/active_support/cache.rb | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

(limited to 'activesupport/lib/active_support/cache.rb')

diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 9848e0c623..395aa5e8f1 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -154,12 +154,11 @@ module ActiveSupport
     #   cache.namespace = -> { @last_mod_time }  # Set the namespace to a variable
     #   @last_mod_time = Time.now  # Invalidate the entire cache by changing namespace
     #
-    # Caches can also store values in a compressed format to save space and
-    # reduce time spent sending data. Since there is overhead, values must be
-    # large enough to warrant compression. To turn on compression either pass
-    # <tt>compress: true</tt> in the initializer or as an option to +fetch+
-    # or +write+. To specify the threshold at which to compress values, set the
-    # <tt>:compress_threshold</tt> option. The default threshold is 16K.
+    # Cached data larger than 1kB are compressed by default. To turn off
+    # compression, pass <tt>compress: false</tt> to the initializer or to
+    # individual +fetch+ or +write+ method calls. The 1kB compression
+    # threshold is configurable with the <tt>:compress_threshold</tt> option,
+    # specified in bytes.
     class Store
       cattr_accessor :logger, instance_writer: true
 
@@ -218,8 +217,7 @@ module ActiveSupport
       # ask whether you should force a cache write. Otherwise, it's clearer to
       # just call <tt>Cache#write</tt>.
       #
-      # Setting <tt>:compress</tt> will store a large cache entry set by the call
-      # in a compressed format.
+      # Setting <tt>compress: false</tt> disables compression of the cache entry.
       #
       # Setting <tt>:expires_in</tt> will set an expiration time on the cache.
       # All caches support auto-expiring content after a specified number of
@@ -664,7 +662,7 @@ module ActiveSupport
     class Entry # :nodoc:
       attr_reader :version
 
-      DEFAULT_COMPRESS_LIMIT = 16.kilobytes
+      DEFAULT_COMPRESS_LIMIT = 1.kilobyte
 
       # Creates a new cache entry for the specified value. Options supported are
       # +:compress+, +:compress_threshold+, and +:expires_in+.
@@ -739,8 +737,8 @@ module ActiveSupport
 
       private
         def should_compress?(value, options)
-          if value && options[:compress]
-            compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT
+          if value && options.fetch(:compress, true)
+            compress_threshold = options.fetch(:compress_threshold, DEFAULT_COMPRESS_LIMIT)
             serialized_value_size = (value.is_a?(String) ? value : Marshal.dump(value)).bytesize
 
             return true if serialized_value_size >= compress_threshold
-- 
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