Status

Current state: Under Discussion

Discussion thread: here

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Motivation

Window size is not passed to the Kafka consumer during windowed aggregations, so the consumer uses the default Long.MAX_VALUE when initializing the deserializer. Both TimeWindowedSerde and TimeWindowedDeserializer have a default constructor that does not require a window size, causing fatal errors at runtime for some programs. 

Public Interfaces

In ConsumerConfig.java add window.size.ms

/** <code>window.size.ms</code> */
public static final String WINDOW_SIZE_MS_CONFIG = "window.size.ms";
private static final String WINDOW_SIZE_MS_DOC = "Passes window size to the deserializer in order to calculate window end times. Default is Long.MAX_VALUE";

Deprecate the following methods

@Deprecated
public TimeWindowedSerde(final Serde<T> inner) {
	super(new TimeWindowedSerializer<>(inner.serializer()), new TimeWindowedDeserializer<>(inner.deserializer()));
}

@Deprecated
public TimeWindowedDeserializer(final Deserializer<T> inner) {
	this(inner, Long.MAX_VALUE);
}

/**
* Construct a {@code TimeWindowedSerde} object for the specified inner class type.
*/
@Deprecated
static public <T> Serde<Windowed<T>> timeWindowedSerdeFrom(final Class<T> type) {
	return new TimeWindowedSerde<>(Serdes.serdeFrom(type));
}

Proposed Changes

Add window.size.ms to the ConsumerConfigs class to ensure that the desired window size is set when the consumer creates the TimeWindowedDeserializer instance. This is relevant for consuming TimeWindowed records directly, which is helpful when testing windowed aggregations. Without this change, all windows will have a size and end time of Long.MAX_VALUE.

Additionally, deprecate constructors in both TimeWindowedDeserializer and WindowedSerdes that don't require a window size. This ensures that the window size would be properly set before encountering any instances where it should be used.

Note that to use the windows.size.ms config through the console consumer (if desired), add the key.deserializer prefix and pass it in as a property.

Compatibility, Deprecation, and Migration Plan

Tests that need to be updated:

• WindowKeySchemaTest
• KStreamAggregationIntegrationTest
• WindowedSerdesTest
• TimeWindowedCogroupedKStreamImplTest

Classes that need to be updated:

• TemperatureDemo
• Serdes

Rejected Alternatives