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https://issues.apache.org/jira/browse/KAFKA-6486?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matthias J. Sax resolved KAFKA-6486.
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Resolution: Fixed
> TimeWindows causes unordered calls to windowed aggregation functions
> --------------------------------------------------------------------
>
> Key: KAFKA-6486
> URL: https://issues.apache.org/jira/browse/KAFKA-6486
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Affects Versions: 1.0.0
> Reporter: Valentino Proietti
> Assignee: Asutosh Pandya
> Priority: Minor
> Fix For: 1.2.0
>
> Attachments: KAFKA-6486.patch
>
>
> This is not a real bug but it causes some weird behaviour, at least in my
> opinion.
> The TimeWindows has a method called windowsFor() that uses and returns an
> HashMap:
> @Override
> *public* Map<Long, TimeWindow> windowsFor(*final* *long* timestamp) {
> *long* windowStart = (Math._max_(0, timestamp - sizeMs + advanceMs) /
> advanceMs) * advanceMs;
> *final* Map<Long, TimeWindow> windows = *new* HashMap<>();
> ....
> the HashMap does not preserve the order of insertion and this ends up later
> in calls to any streams windowed aggregation functions that are not ordered
> by window time as I would expect.
> A simple solution is to replace the HashMap with a LinkedHashMap and that's
> what I did.
> Anyway replacing it directly in your code can save hours of debugging to
> understand what's happening.
> Thank you
>
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