MemCacheStore: Support expiring counters

Support `expires_in` in `ActiveSupport::Cache::MemCacheStore#increment`
and `#decrement`.

Closes #30716.

3 files changed, 31 insertions, 2 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 904dab0e05..88bbafc3a8 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,16 @@
+*   MemCacheStore: Support expiring counters.
+
+    Pass `expires_in: [seconds]` to `#increment` and `#decrement` options
+    to set the Memcached TTL (time-to-live) if the counter doesn't exist.
+    If the counter exists, Memcached doesn't extend its expiry when it's
+    incremented or decremented.
+
+    ```
+    Rails.cache.increment("my_counter", 1, expires_in: 2.minutes)
+    ```
+
+    *Takumasa Ochi*
+
 *   Handle `TZInfo::AmbiguousTime` errors
 
     Make `ActiveSupport::TimeWithZone` match Ruby's handling of ambiguous
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index 9242a334f2..50f072388d 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -122,7 +122,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:increment, name, amount: amount) do
           rescue_error_with nil do
-            @data.incr(normalize_key(name, options), amount)
+            @data.incr(normalize_key(name, options), amount, options[:expires_in])
           end
         end
       end
@@ -135,7 +135,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:decrement, name, amount: amount) do
           rescue_error_with nil do
-            @data.decr(normalize_key(name, options), amount)
+            @data.decr(normalize_key(name, options), amount, options[:expires_in])
           end
         end
       end
diff --git a/activesupport/test/cache/stores/mem_cache_store_test.rb b/activesupport/test/cache/stores/mem_cache_store_test.rb
index 1b73fb65eb..99624caf8a 100644
--- a/activesupport/test/cache/stores/mem_cache_store_test.rb
+++ b/activesupport/test/cache/stores/mem_cache_store_test.rb
@@ -57,6 +57,22 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     end
   end
 
+  def test_increment_expires_in
+    cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
+    cache.clear
+    assert_called_with cache.instance_variable_get(:@data), :incr, [ "foo", 1, 60 ] do
+      cache.increment("foo", 1, expires_in: 60)
+    end
+  end
+
+  def test_decrement_expires_in
+    cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
+    cache.clear
+    assert_called_with cache.instance_variable_get(:@data), :decr, [ "foo", 1, 60 ] do
+      cache.decrement("foo", 1, expires_in: 60)
+    end
+  end
+
   def test_local_cache_raw_values_with_marshal
     cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
     cache.clear