Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/5239#discussion_r165343607
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/SnapshotStrategy.java
---
@@ -0,0 +1,50 @@
+/*
+ * 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.flink.runtime.state;
+
+import org.apache.flink.runtime.checkpoint.CheckpointOptions;
+
+import java.util.concurrent.RunnableFuture;
+
+/**
+ * Interface for different snapshot approaches in state backends.
Implementing classes should ideally be stateless or at
+ * least threadsafe, i.e. this is a functional interface and is can be
called in parallel by multiple checkpoints.
+ *
+ * @param <S> type of the returned state object that represents the result
of the snapshot operation.
+ */
+public interface SnapshotStrategy<S extends StateObject> {
--- End diff --
If this interface is functional, then we could also annotate it with
`@FunctionalInterface`
---
