Add :expires_in support to increment and decrement (#120)

Keeps feature parity between **redis-activesupport** and `ActiveSupport::Cache::RedisCacheStore`.

Author: fanjieqi

lib/active_support/cache/redis_store.rb

@@ -187,11 +187,17 @@ def fetch_multi(*names)
       #
       #   cache.increment "rabbit"
       #   cache.read "rabbit", :raw => true       # => "1"
-      def increment(key, amount = 1, options = {})
-        options = merged_options(options)
-        instrument(:increment, key, :amount => amount) do
-          failsafe(:increment) do
-            with{|c| c.incrby normalize_key(key, options), amount}
+      def increment(name, amount = 1, options = {})
+        instrument :increment, name, amount: amount do
+          failsafe :increment do
+            options = merged_options(options)
+            key = normalize_key(name, options)
+
+            with do |c|
+              c.incrby(key, amount).tap do
+                write_key_expiry(c, key, options)
+              end
+            end
           end
         end
       end
@@ -217,11 +223,17 @@ def increment(key, amount = 1, options = {})
       #
       #   cache.decrement "rabbit"
       #   cache.read "rabbit", :raw => true       # => "-1"
-      def decrement(key, amount = 1, options = {})
-        options = merged_options(options)
-        instrument(:decrement, key, :amount => amount) do
-          failsafe(:decrement) do
-            with{|c| c.decrby normalize_key(key, options), amount}
+      def decrement(name, amount = 1, options = {})
+        instrument :decrement, name, amount: amount do
+          failsafe :decrement do
+            options = merged_options(options)
+            key = normalize_key(name, options)
+
+            with do |c|
+              c.decrby(key, amount).tap do
+                write_key_expiry(c, key, options)
+              end
+            end
           end
         end
       end
@@ -279,6 +291,12 @@ def read_entry(key, options)
           end
         end
 
+        def write_key_expiry(client, key, options)
+          if options[:expires_in] && client.ttl(key) < 0
+            client.expire key, options[:expires_in].to_i
+          end
+        end
+
         ##
         # Implement the ActiveSupport::Cache#delete_entry
         #

test/active_support/cache/redis_store_test.rb

@@ -335,6 +335,24 @@ def setup
     end
   end
 
+  it "increments a key with expiration time" do
+    with_store_management do |store|
+      store.increment "counter", 1, :expires_in => 1.second
+      store.read("counter", :raw => true).to_i.must_equal(1)
+      sleep 2
+      store.read("counter", :raw => true).must_be_nil
+    end
+  end
+
+  it "decrements a key with expiration time" do
+    with_store_management do |store|
+      store.decrement "counter", 1, :expires_in => 1.second
+      store.read("counter", :raw => true).to_i.must_equal(-1)
+      sleep 2
+      store.read("counter", :raw => true).must_be_nil
+    end
+  end
+
   it "clears the store" do
     with_store_management do |store|
       store.clear