Merge pull request rails#54855 from ghiculescu/read_counter

Add `Cache#read_counter` and `Cache#write_counter`

Author: byroot

activesupport/CHANGELOG.md

@@ -1,3 +1,14 @@
+* Add `Cache#read_counter` and `Cache#write_counter`
+
+ ```ruby
+ Rails.cache.write_counter("foo", 1)
+ Rails.cache.read_counter("foo") # => 1
+ Rails.cache.increment("foo")
+ Rails.cache.read_counter("foo") # => 2
+ ```
+
+ *Alex Ghiculescu*
+
 * Introduce ActiveSupport::Testing::ErrorReporterAssertions#capture_error_reports
 
  Captures all reported errors from within the block that match the given

activesupport/lib/active_support/cache.rb

@@ -743,6 +743,32 @@ def decrement(name, amount = 1, options = nil)
  raise NotImplementedError.new("#{self.class.name} does not support decrement")
  end
 
+ # Reads a counter that was set by #increment / #decrement.
+ #
+ # cache.write_counter("foo", 1)
+ # cache.read_counter("foo") # => 1
+ # cache.increment("foo")
+ # cache.read_counter("foo") # => 2
+ #
+ # Options are passed to the underlying cache implementation.
+ def read_counter(name, **options)
+ options = merged_options(options).merge(raw: true)
+ read(name, **options)&.to_i
+ end
+
+ # Writes a counter that can then be modified by #increment / #decrement.
+ #
+ # cache.write_counter("foo", 1)
+ # cache.read_counter("foo") # => 1
+ # cache.increment("foo")
+ # cache.read_counter("foo") # => 2
+ #
+ # Options are passed to the underlying cache implementation.
+ def write_counter(name, value, **options)
+ options = merged_options(options).merge(raw: true)
+ write(name, value.to_i, **options)
+ end
+
  # Cleans up the cache by removing expired entries.
  #
  # Options are passed to the underlying cache implementation.

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -126,6 +126,11 @@ def inspect
  #
  # Incrementing a non-numeric value, or a value written without
  # <tt>raw: true</tt>, will fail and return +nil+.
+ #
+ # To read the value later, call #read_counter:
+ #
+ # cache.increment("baz") # => 7
+ # cache.read_counter("baz") # 7
  def increment(name, amount = 1, options = nil)
  options = merged_options(options)
  key = normalize_key(name, options)
@@ -152,6 +157,11 @@ def increment(name, amount = 1, options = nil)
  #
  # Decrementing a non-numeric value, or a value written without
  # <tt>raw: true</tt>, will fail and return +nil+.
+ #
+ # To read the value later, call #read_counter:
+ #
+ # cache.decrement("baz") # => 3
+ # cache.read_counter("baz") # 3
  def decrement(name, amount = 1, options = nil)
  options = merged_options(options)
  key = normalize_key(name, options)

activesupport/lib/active_support/cache/redis_cache_store.rb

@@ -250,6 +250,11 @@ def delete_matched(matcher, options = nil)
  # Incrementing a non-numeric value, or a value written without
  # <tt>raw: true</tt>, will fail and return +nil+.
  #
+ # To read the value later, call #read_counter:
+ #
+ # cache.increment("baz") # => 7
+ # cache.read_counter("baz") # 7
+ #
  # Failsafe: Raises errors.
  def increment(name, amount = 1, options = nil)
  options = merged_options(options)
@@ -277,6 +282,11 @@ def increment(name, amount = 1, options = nil)
  # Decrementing a non-numeric value, or a value written without
  # <tt>raw: true</tt>, will fail and return +nil+.
  #
+ # To read the value later, call #read_counter:
+ #
+ # cache.decrement("baz") # => 3
+ # cache.read_counter("baz") # 3
+ #
  # Failsafe: Raises errors.
  def decrement(name, amount = 1, options = nil)
  options = merged_options(options)

activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb

@@ -31,6 +31,18 @@ def test_decrement
  assert_equal @cache.is_a?(ActiveSupport::Cache::MemCacheStore) ? 0 : -100, missing
  end
 
+ def test_read_counter_and_write_counter
+ key = SecureRandom.uuid
+ @cache.write_counter(key, 1)
+ assert_equal 1, @cache.read(key, raw: true).to_i
+
+ assert_equal 1, @cache.read_counter(key)
+ assert_equal 2, @cache.increment(key)
+ assert_equal 2, @cache.read_counter(key)
+
+ assert_nil @cache.read_counter(SecureRandom.alphanumeric)
+ end
+
  def test_ttl_isnt_updated
  key = SecureRandom.uuid