Merge pull request #444 from weibel/master

Add Memcached cache client.

examples/autoexpire_cache_dalli.rb

+# This class implements a cache with simple delegation to the the Dalli Memcached client
+# https://github.com/mperham/dalli
+#
+# A TTL is set on initialization
+
+class AutoexpireCacheDalli
+  def initialize(store, ttl = 86400)
+    @store = store
+    @keys = 'GeocoderDalliClientKeys'
+    @ttl = ttl
+  end
+
+  def [](url)
+    res = @store.get(url)
+    res = YAML::load(res) if res.present?
+    res
+  end
+
+  def []=(url, value)
+    if value.nil?
+      del(url)
+    else
+      key_cache_add(url) if @store.add(key, YAML::dump(value), @ttl)
+    end
+    value
+  end
+
+  def keys
+    key_cache
+  end
+
+  def del(url)
+    key_cache_delete(url) if @store.delete(key)
+  end
+
+  private
+
+  def key_cache
+    the_keys = @store.get(@keys)
+    if the_keys.nil?
+      @store.add(@keys, YAML::dump([]))
+      []
+    else
+      YAML::load(the_keys)
+    end
+  end
+
+  def key_cache_add(key)
+    @store.replace(@keys, YAML::dump(key_cache << key))
+  end
+
+  def key_cache_delete(key)
+    tmp = key_cache
+    tmp.delete(key)
+    @store.replace(@keys, YAML::dump(tmp))
+  end
+end
+
+# Here Dalli is set up as on Heroku using the Memcachier gem.
+# https://devcenter.heroku.com/articles/memcachier#ruby
+# On other setups you might have to specify your Memcached server in Dalli::Client.new
+Geocoder.configure(:cache => AutoexpireCacheDalli.new(Dalli::Client.new))

examples/autoexpire_cache.rb → examples/autoexpire_cache_redis.rb

 # This class implements a cache with simple delegation to the Redis store, but
 # when it creates a key/value pair, it also sends an EXPIRE command with a TTL.
 # It should be fairly simple to do the same thing with Memcached.
-class AutoexpireCache
-  def initialize(store)
+class AutoexpireCacheRedis
+  def initialize(store, ttl = 86400)
     @store = store
-    @ttl = 86400
+    @ttl = ttl
   end
 
   def [](url)
@@ -25,4 +25,4 @@ class AutoexpireCache
   end
 end
 
-Geocoder.configure(:cache => AutoexpireCache.new(Redis.new))
+Geocoder.configure(:cache => AutoexpireCacheRedis.new(Redis.new))
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