Bruno Cadonna created KAFKA-8755:
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Summary: Stand-by Task of an Optimized Source Table Does Not Write
Anything to its State Store
Key: KAFKA-8755
URL: https://issues.apache.org/jira/browse/KAFKA-8755
Project: Kafka
Issue Type: Bug
Components: streams
Affects Versions: 2.4.0
Reporter: Bruno Cadonna
Attachments: StandbyTaskTest.java
With the following topology:
{code:java}
builder.table(
INPUT_TOPIC,
Consumed.with(Serdes.Integer(), Serdes.Integer()),
Materialized.<Integer, Integer, KeyValueStore<Bytes, byte[]>>as(stateName)
)
{code}
and with topology optimization turned on, Kafka Streams uses the input topic
{{INPUT_TOPIC}} as the change log topic for state store {{stateName}}. A
stand-by task for such a topology should read from {{INPUT_TOPIC}} and should
write the records to its state store so that the streams client that runs the
stand-by task can take over the execution of the topology in case of a failure
with an up-to-date replica of the state.
Currently, the stand-by task described above reads from the input topic but
does not write the records to its state store. Thus, after a failure the
stand-by task cannot provide any up-to-date state store and the streams client
needs to construct the state from scratch before it can take over the execution.
The described behaviour can be reproduced with the attached test.
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