[KAFKA-12313] Consider deprecating the default.windowed.serde.inner.class configs - ASF JIRA

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Details

Type: Improvement
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 3.0.0
Component/s: streams
Labels:
- needs-kip

Description

During the discussion of KIP-659 we discussed whether it made sense to have a "default" class for the serdes of windowed inner classes across Streams. Using these configs instead of specifying an actual Serde object can lead to subtle bugs, since the WindowedDeserializer requires a windowSize in addition to the inner class. If the default constructor is invoked, as it will be when falling back on the config, this windowSize defaults to MAX_VALUE.

If the downstream program doesn't care about the window end time in the output, then this can go unnoticed and technically there is no problem. But if anything does depend on the end time, or the user just wants to manually read the output for testing purposes, then the MAX_VALUE will result in a garbage timestamp.

We should consider whether the convenience of specifying a config instead of instantiating a Serde in each operator is really worth the risk of a user accidentally failing to specify a windowSize