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https://issues.apache.org/jira/browse/FLINK-9637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16561293#comment-16561293
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ASF GitHub Bot commented on FLINK-9637:
---------------------------------------
eliaslevy commented on a change in pull request #6379: [FLINK-9637] Add public
user documentation for state TTL feature
URL: https://github.com/apache/flink/pull/6379#discussion_r205990785
##########
File path: docs/dev/stream/state/state.md
##########
@@ -266,6 +266,92 @@ a `ValueState`. Once the count reaches 2 it will emit the
average and clear the
we start over from `0`. Note that this would keep a different state value for
each different input
key if we had tuples with different values in the first field.
+### State time-to-live (TTL)
+
+A time-to-live (TTL) can be assigned to the keyed state value.
+In this case it will expire after the configured TTL
+and its stored value will be cleaned up based on the best effort.
+Depending on configuration, the expired state can become unavailable for read
access
+even if it is not cleaned up yet. In this case it behaves as if it does not
exist any more.
+
+The collection types of state support TTL on entry level:
+separate list elements and map entries expire independently.
+
+The behaviour of state with TTL firstly should be configured by building
`StateTtlConfiguration`:
+
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+{% highlight java %}
+StateTtlConfiguration ttlConfig = StateTtlConfiguration
+ .newBuilder(Time.seconds(1))
+ .setTtlUpdateType(StateTtlConfiguration.TtlUpdateType.OnCreateAndWrite)
+
.setStateVisibility(StateTtlConfiguration.TtlStateVisibility.NeverReturnExpired)
+ .build();
+{% endhighlight %}
+</div>
+
+<div data-lang="scala" markdown="1">
+{% highlight scala %}
+val ttlConfig = StateTtlConfiguration
+ .newBuilder(Time.seconds(1))
+ .setTtlUpdateType(StateTtlConfiguration.TtlUpdateType.OnCreateAndWrite)
+
.setStateVisibility(StateTtlConfiguration.TtlStateVisibility.NeverReturnExpired)
+ .build()
+{% endhighlight %}
+</div>
+</div>
+
+It has several options to consider.
+The first parameter of `newBuilder` method is mandatory, it is a value of
time-to-live itself.
+
+The update type configures when the time-to-live of state value is prolonged
(default `OnCreateAndWrite`):
Review comment:
The update type configures when the state TTL is refreshed (default
`OnCreateAndWrite`):
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> Add public user documentation for TTL feature
> ---------------------------------------------
>
> Key: FLINK-9637
> URL: https://issues.apache.org/jira/browse/FLINK-9637
> 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
>
>
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