Consumer's properties are also used for a producer to retry

[ta7uw]

The following type of warning occurs many times when using the retry mechanism of decaton.

The configuration 'group.id' was supplied but isn't a known config.

This warning occurs when a producer is given unused properties.

https://github.com/apache/kafka/blob/779f1444f128e9d77486243cb94d7efcdea26f52/clients/src/main/java/org/apache/kafka/common/config/AbstractConfig.java#L353-L355

I found that the following code causes this warning.

decaton/processor/src/main/java/com/linecorp/decaton/processor/runtime/SubscriptionBuilder.java

Lines 139 to 140 in cd7cbbb

	Properties producerConfig = Optional.ofNullable(retryConfig.producerConfig())
	.orElse(consumerConfig);

Properties for a consumer are also used for properties for a retry producer.
I think this behavior is designed to set bootstrap.servers and so on without settings for retry.
But, more consumer's properties there are, the more warnings may occur.
It might be a good idea to filter consumer's properties in order to set the properties to a retry producer without warnings.

[kawamuray]

Thanks for reporting :)

It might be a good idea to filter consumer's properties in order to set the properties to a retry producer without warnings.

Right, we were aware of this occurrences of warn logs but it's something better to not to have.
I think suppressing it is possible just by taking intersection between producerConfig and kafka-client's ProducerConfig.configNames() -> Set<String>.

Would you be interested in sending a PR for that?

[ta7uw]

Would you be interested in sending a PR for that?

Yes, I will create a PR.