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https://issues.apache.org/jira/browse/FLINK-9513?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16527980#comment-16527980
 ] 

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

Github user azagrebin commented on a diff in the pull request:

    https://github.com/apache/flink/pull/6196#discussion_r199226833
  
    --- Diff: 
flink-runtime/src/main/java/org/apache/flink/runtime/state/ttl/TtlStateFactory.java
 ---
    @@ -0,0 +1,207 @@
    +/*
    + * 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 java.util.Arrays;
    +import java.util.List;
    +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.
    + */
    +public class TtlStateFactory {
    +   public static <N, SV, S extends State, IS extends S> IS 
createStateAndWrapWithTtlIfEnabled(
    +           TypeSerializer<N> namespaceSerializer,
    +           StateDescriptor<S, SV> stateDesc,
    +           KeyedStateFactory originalStateFactory,
    +           TtlConfig ttlConfig,
    +           TtlTimeProvider timeProvider) throws Exception {
    +           return ttlConfig.getTtlUpdateType() == TtlUpdateType.Disabled ?
    +                   originalStateFactory.createState(namespaceSerializer, 
stateDesc) :
    +                   new TtlStateFactory(originalStateFactory, ttlConfig, 
timeProvider)
    +                           .createState(namespaceSerializer, stateDesc);
    +   }
    +
    +   private final Map<Class<? extends StateDescriptor>, StateFactory> 
stateFactories;
    --- End diff --
    
    I think creating the map is not a big deal because it will happen on init 
without big pressure on GC. Also map is more declarative and flexible if new 
state needs to be added then just the map needs to be modified but not the 
method. Or if needed in future, it can be easier refactored to build the 
mapping somewhere else and inject it into factory.


> 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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