diff --git a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/DocumentNodeStore.java b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/DocumentNodeStore.java
index 061a364..842613f 100644
--- a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/DocumentNodeStore.java
+++ b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/DocumentNodeStore.java
@@ -104,6 +104,7 @@ import org.apache.jackrabbit.oak.spi.commit.CommitHook;
 import org.apache.jackrabbit.oak.spi.commit.CommitInfo;
 import org.apache.jackrabbit.oak.spi.commit.Observer;
 import org.apache.jackrabbit.oak.spi.state.AbstractNodeState;
+import org.apache.jackrabbit.oak.spi.state.Clusterable;
 import org.apache.jackrabbit.oak.spi.state.NodeBuilder;
 import org.apache.jackrabbit.oak.spi.state.NodeState;
 import org.apache.jackrabbit.oak.spi.state.NodeStateDiff;
@@ -117,7 +118,7 @@ import org.slf4j.LoggerFactory;
  * Implementation of a NodeStore on {@link DocumentStore}.
  */
 public final class DocumentNodeStore
-        implements NodeStore, RevisionContext, Observable {
+        implements NodeStore, RevisionContext, Observable, Clusterable {
 
     private static final Logger LOG = LoggerFactory.getLogger(DocumentNodeStore.class);
 
@@ -2659,4 +2660,9 @@ public final class DocumentNodeStore
     public void setPersistentCache(PersistentCache persistentCache) {
         this.persistentCache = persistentCache;
     }
+
+    @Override
+    public String getInstanceId() {
+        return String.valueOf(getClusterId());
+    }
 }
diff --git a/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/state/Clusterable.java b/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/state/Clusterable.java
new file mode 100644
index 0000000..d94e7ab
--- /dev/null
+++ b/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/state/Clusterable.java
@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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.apache.jackrabbit.oak.spi.state;
+
+import javax.annotation.Nonnull;
+
+/**
+ * Defines a clusterable persistence implementation. Normally associated with a {@link NodeStore}.
+ */
+public interface Clusterable {
+    /**
+     * <p>
+     * Will return a unique number per instance across the cluster. It will only make its best
+     * effort to preserve the same number across restarts but it must be unique across the cluster.
+     * </p>
+     * <p>
+     *  It may be the same as a cluster id.
+     * </p>
+     * 
+     * @return Cannot be null or empty.
+     */
+    @Nonnull
+    String getInstanceId();
+}