Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/6196#discussion_r199477483
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/ttl/TtlStateFactory.java
---
@@ -0,0 +1,210 @@
+/*
+ * 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.ttl;
+
+import org.apache.flink.api.common.state.AggregatingStateDescriptor;
+import org.apache.flink.api.common.state.FoldingStateDescriptor;
+import org.apache.flink.api.common.state.ListStateDescriptor;
+import org.apache.flink.api.common.state.MapStateDescriptor;
+import org.apache.flink.api.common.state.ReducingStateDescriptor;
+import org.apache.flink.api.common.state.State;
+import org.apache.flink.api.common.state.StateDescriptor;
+import org.apache.flink.api.common.state.ValueStateDescriptor;
+import org.apache.flink.api.common.typeutils.CompositeSerializer;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.api.common.typeutils.base.LongSerializer;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.runtime.state.KeyedStateFactory;
+import org.apache.flink.util.FlinkRuntimeException;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nonnull;
+
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+/**
+ * This state factory wraps state objects, produced by backends, with TTL
logic.
+ */
+@SuppressWarnings("unchecked")
+public class TtlStateFactory {
--- End diff --
It might make sense to also have a test when we introduce a new class that
provides some kind of "service", e.g. to check that all the types are correctly
mapped and also prevent that somebody breaks the mapping by accident.
---
