add logic for replicating writes and reads to stores

storehaus-core/src/main/scala/com/twitter/storehaus/ReplicatedStore.scala

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2013 Twitter Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License. You may obtain
+ * a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.twitter.storehaus
+
+import com.twitter.util.Future
+
+import Store.{selectFirstSuccessfulTrial => selectFirst}
+
+/**
+ * Replicates writes to all stores, and takes the first successful read.
+ */
+class ReplicatedStore[StoreType <: Store[StoreType, K, V], K, V](stores: Seq[StoreType])
+    extends Store[ReplicatedStore[StoreType, K, V], K, V] {
+  override def get(k: K) = selectFirst(stores.map { _.get(k) })
+  override def multiGet(ks: Set[K]) = selectFirst(stores.map { _.multiGet(ks) })
+  override def update(k: K)(fn: Option[V] => Option[V]) =
+    Future.collect(stores.map { _.update(k)(fn) }).map { new ReplicatedStore(_) }
+  override def -(k: K) =
+    Future.collect(stores.map { _ - k }).map { new ReplicatedStore(_) }
+  override def +(pair: (K,V)) =
+    Future.collect(stores.map { _ + pair }).map { new ReplicatedStore(_) }
+}

storehaus-core/src/test/scala/com/twitter/storehaus/ReplicatedStoreProperties.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2013 Twitter Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License. You may obtain
+ * a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.twitter.storehaus
+
+import org.scalacheck.Properties
+
+object ReplicatedStoreProperties extends Properties("ReplicatedStore") {
+  import StoreProperties.storeTest
+
+  property("ReplicatedStore test") =
+    storeTest[ReplicatedStore[MapStore[String, Int], String, Int], String, Int](new ReplicatedStore(
+        Stream.continually(new MapStore[String, Int]()).take(100).toSeq))
+}