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https://issues.apache.org/jira/browse/FLINK-16929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17076112#comment-17076112
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Ori Popowski commented on FLINK-16929:
--------------------------------------
[~aljoscha]
Looking at discussions
([1|https://www.mail-archive.com/user@flink.apache.org/msg08755.html]) and
([2|https://www.mail-archive.com/user@flink.apache.org/msg09507.html]) from the
mailing list, I conclude that there could be two reasons for this problem:
# The window's trigger is {{FIRE_AND_PURGE}}.
# The {{allowedLateness}} is not {{0}}.
We have neither of those definitions, and I clearly see that late events
trigger the window.
I even see that if I have a session whose all events are late by, say, 30
minutes, then every event creates a new session.
I've thoroughly went over the code and made sure that the trigger and
{{allowedLateness}} are correct and we're still experiencing this behavior.
> Session Window produces sessions randomly
> -----------------------------------------
>
> Key: FLINK-16929
> URL: https://issues.apache.org/jira/browse/FLINK-16929
> Project: Flink
> Issue Type: Bug
> Affects Versions: 1.9.1
> Reporter: Ori Popowski
> Priority: Major
> Attachments: image-2020-04-01-19-56-00-239.png,
> image-2020-04-01-19-56-27-720.png
>
>
> We have a Flink job which keyBys session ID (sId), and uses a session window
> with 30 minutes gap:
> {code:java}
> inputStream
> .keyBy(keySelector)
> .window(EventTimeSessionWindows.withGap(Time.minutes(30)))
> .allowedLateness(Time.seconds(0L))
> {code}
> This Flink job reads from Kinesis stream.
> Lately (I suspect after upgrading from 1.5.4 to 1.9.1) we get too many
> sessions, with gaps of several seconds (instead of 30 minutes).
> We have no idea why it's happening and suspect a Flink bug or a state backend
> bug (we use RocksDB).
> I haven't found any indication in the logs except for some read throughput
> warnings which were resolved by a backoff.
> Attached is a table of derived sessions, and then the raw events
> *Sessions*
> !image-2020-04-01-19-56-00-239.png|width=753,height=406!
>
> *Events*
>
> !image-2020-04-01-19-56-27-720.png|width=312,height=383!
>
>
>
>
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