Apparent Silent Data loss when Schema Registry is mistakenly in READONLY

[johnjcasey]

I've been testing a few use cases, and I found an issue where silent data loss appears to occur under the following conditions with Kafka Connect and Schema Registry

1. Using a Source connector (Pub/Sub Source, though I don't think the specific source is the issue here)
2. Using the Avro converter
3. The Schema Registry itself is in READONLY mode
4. The schema in question is 'new' to the schema registry.

I create a connector using the avro converter, and looking at the Kafka connect logs, I see 0 exceptions.
However, all the messages are acked on the PubSub side of things, and I see 0 data on the Kafka topic in question.

When I switch the Schema Registry to READWRITE, it works as expected.

I'm not surprised by the failure here, as with no ability to write to Schema Registry the transformation should fail, but I'm concerned by not seeing any exceptions in the logs arising from the failure to convert. Its not entirely clear to me where these exceptions are getting swallowed, but I would expect to see them in the logs.