Michał created KAFKA-8924:
-----------------------------
Summary: Default grace period (-1) of TimeWindows causes suppress
to never emit events
Key: KAFKA-8924
URL: https://issues.apache.org/jira/browse/KAFKA-8924
Project: Kafka
Issue Type: Bug
Components: streams
Affects Versions: 2.3.0
Reporter: Michał
#Problem
The default creation of TimeWindows, like
```
TimeWindows.of(ofMillis(xxx))
```
calls an internal constructor
```
return new TimeWindows(sizeMs, sizeMs, -1, DEFAULT_RETENTION_MS);
```
And the *-1* parameter is the default grace period which I think is here for
backward compatibility
```
@SuppressWarnings("deprecation") // continuing to support
Windows#maintainMs/segmentInterval in fallback mode
@Override
public long gracePeriodMs() {
// NOTE: in the future, when we remove maintainMs,
// we should default the grace period to 24h to maintain the default
behavior,
// or we can default to (24h - size) if you want to be super accurate.
return graceMs != -1 ? graceMs : maintainMs() - size();
}
```
The problem is that if you use a TimeWindows with gracePeriod of *-1* together
with suppress *untilWindowCloses*, it never emits an event.
You can check the Suppress tests
(SuppressScenarioTest.shouldSupportFinalResultsForTimeWindows), where
[~vvcephei] was (maybe) aware of that and all the scenarios specify the
gracePeriod.
I will add a test without it on my branch and it will fail.
#Now what can be done
One easy fix would be to change the default value to 0, which works fine for me
in my project, however, I am not aware of the impact it would have done due to
the changes in the *gracePeriodMs* method mentioned before.
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