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https://issues.apache.org/jira/browse/FLINK-9513?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16529797#comment-16529797
 ] 

ASF GitHub Bot commented on FLINK-9513:
---------------------------------------

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.


> Wrap state binder with TTL logic
> --------------------------------
>
>                 Key: FLINK-9513
>                 URL: https://issues.apache.org/jira/browse/FLINK-9513
>             Project: Flink
>          Issue Type: Sub-task
>          Components: State Backends, Checkpointing
>    Affects Versions: 1.6.0
>            Reporter: Andrey Zagrebin
>            Assignee: Andrey Zagrebin
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.6.0
>
>
> The main idea is to wrap user state value with a class holding the value and 
> the expiration timestamp (maybe meta data in future) and use the new object 
> as a value in the existing implementations:
> {code:java}
> class TtlValue<V> {
>   V value;
>   long expirationTimestamp;
> }
> {code}
> The original state binder factory is wrapped with TtlStateBinder if TTL is 
> enabled:
> {code:java}
> state = ttlConfig.updateType == DISABLED ?
>  bind(binder) : bind(new TtlStateBinder(binder, timerService));
> {code}
> TtlStateBinder decorates the states produced by the original binder with TTL 
> logic wrappers and adds TtlValue serialisation logic:
> {code:java}
> TtlStateBinder {
>     StateBinder binder;
>     ProcessingTimeProvier timeProvider; // System.currentTimeMillis()
>     <V> TtlValueState<V> createValueState(valueDesc) {
>          serializer = new TtlValueSerializer(valueDesc.getSerializer);
>          ttlValueDesc = new ValueDesc(serializer, ...);
>          // or implement custom TypeInfo
>          originalStateWithTtl = binder.createValueState(valueDesc);
>          return new TtlValueState(originalStateWithTtl, timeProvider);
>     }
>       // List, Map, ...
> }
> {code}
> TTL serializer should add expiration timestamp



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