fix: workaround MemCacheClient + MemCache backend by using a dedicated proxy

lib/rack/attack.rb

@@ -2,18 +2,19 @@ require 'rack'
 require 'forwardable'
 
 class Rack::Attack
-  autoload :Cache,           'rack/attack/cache'
-  autoload :Check,           'rack/attack/check'
-  autoload :Throttle,        'rack/attack/throttle'
-  autoload :Whitelist,       'rack/attack/whitelist'
-  autoload :Blacklist,       'rack/attack/blacklist'
-  autoload :Track,           'rack/attack/track'
-  autoload :StoreProxy,      'rack/attack/store_proxy'
-  autoload :DalliProxy,      'rack/attack/store_proxy/dalli_proxy'
-  autoload :RedisStoreProxy, 'rack/attack/store_proxy/redis_store_proxy'
-  autoload :Fail2Ban,        'rack/attack/fail2ban'
-  autoload :Allow2Ban,       'rack/attack/allow2ban'
-  autoload :Request,         'rack/attack/request'
+  autoload :Cache,              'rack/attack/cache'
+  autoload :Check,              'rack/attack/check'
+  autoload :Throttle,           'rack/attack/throttle'
+  autoload :Whitelist,          'rack/attack/whitelist'
+  autoload :Blacklist,          'rack/attack/blacklist'
+  autoload :Track,              'rack/attack/track'
+  autoload :StoreProxy,         'rack/attack/store_proxy'
+  autoload :DalliProxy,         'rack/attack/store_proxy/dalli_proxy'
+  autoload :MemCacheProxy,      'rack/attack/store_proxy/mem_cache_proxy'
+  autoload :RedisStoreProxy,    'rack/attack/store_proxy/redis_store_proxy'
+  autoload :Fail2Ban,           'rack/attack/fail2ban'
+  autoload :Allow2Ban,          'rack/attack/allow2ban'
+  autoload :Request,            'rack/attack/request'
 
   class << self
 

lib/rack/attack/store_proxy.rb

@@ -1,7 +1,7 @@
 module Rack
   class Attack
     module StoreProxy
-      PROXIES = [DalliProxy, RedisStoreProxy]
+      PROXIES = [DalliProxy, MemCacheProxy, RedisStoreProxy]
 
       def self.build(store)
         # RedisStore#increment needs different behavior, so detect that
@@ -14,7 +14,7 @@ module Rack
           # We also want to use the underlying Dalli client instead of ::ActiveSupport::Cache::MemCacheStore,
           # but not the Memcache client if using Rails 3.x
           client = store.instance_variable_get(:@data)
-          if client.is_a?(Redis::Store) || client.is_a?(Dalli::Client)
+          if client.is_a?(Redis::Store) || client.is_a?(Dalli::Client) || client.is_a?(MemCache)
             store = store.instance_variable_get(:@data)
           end
         end

lib/rack/attack/store_proxy/mem_cache_proxy.rb

@@ -0,0 +1,51 @@
+module Rack
+  class Attack
+    module StoreProxy
+      class MemCacheProxy < SimpleDelegator
+        def self.handle?(store)
+          defined?(::MemCache) && store.is_a?(::MemCache)
+        end
+
+        def initialize(store)
+          super(store)
+          stub_with_if_missing
+        end
+
+        def read(key)
+          # Second argument: reading raw value
+          get(key, true)
+          rescue MemCache::MemCacheError
+        end
+
+        def write(key, value, options={})
+          # Third argument: writing raw value
+          set(key, value, options.fetch(:expires_in, 0), true)
+        rescue MemCache::MemCacheError
+        end
+
+        def increment(key, amount, options={})
+          incr(key, amount)
+        rescue MemCache::MemCacheError
+        end
+
+        def delete(key, options={})
+          with do |client|
+            client.delete(key)
+          end
+        rescue MemCache::MemCacheError
+        end
+
+        private
+
+        def stub_with_if_missing
+          unless __getobj__.respond_to?(:with)
+            class << self
+              def with; yield __getobj__; end
+            end
+          end
+        end
+
+      end
+    end
+  end
+end