1 files changed, 47 insertions, 0 deletions
diff --git a/src/main/java/org/elasticsearch/cluster/routing/ShardShuffler.java b/src/main/java/org/elasticsearch/cluster/routing/ShardShuffler.java
new file mode 100644
index 0000000..35ea17e
--- /dev/null
+++ b/src/main/java/org/elasticsearch/cluster/routing/ShardShuffler.java
@@ -0,0 +1,47 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.cluster.routing;
+
+import java.util.List;
+
+/**
+ * A shuffler for shards whose primary goal is to balance load.
+ */
+public abstract class ShardShuffler {
+
+    /**
+     * Return a new seed.
+     */
+    public abstract int nextSeed();
+
+    /**
+     * Return a shuffled view over the list of shards. The behavior of this method must be deterministic: if the same list and the same seed
+     * are provided twice, then the result needs to be the same.
+     */
+    public abstract List<ShardRouting> shuffle(List<ShardRouting> shards, int seed);
+
+    /**
+     * Equivalent to calling <code>shuffle(shards, nextSeed())</code>.
+     */
+    public List<ShardRouting> shuffle(List<ShardRouting> shards) {
+        return shuffle(shards, nextSeed());
+    }
+
+}