[FLINK-15904] Make Kafka Consumer work with activated "disableGenericTypes()"

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.10.1, 1.11.0
• Component/s: Connectors / Kafka
• Labels: pull-request-available
• Assignee: Oleksandr Nitavskyi
• Reporter: Aljoscha Krettek
• Created: 04/Feb/20 13:28
• Updated: 03/Jun/20 13:09
• Resolved: 20/Feb/20 17:00

Description

A user reported a problem that the Kafka Consumer doesn't work in that case: https://lists.apache.org/thread.html/r462a854e8a0ab3512e2906b40411624f3164ea3af7cba61ee94cd760%40%3Cuser.flink.apache.org%3E. We should use a different constructor for ListStateDescriptor that takes TypeSerializer here: https://github.com/apache/flink/blob/68cc21e4af71505efa142110e35a1f8b1c25fe6e/flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaConsumerBase.java#L860. This will circumvent the check.

My full analysis from the email thread:

Unfortunately, the fact that the Kafka Sources use Kryo for state serialization is a very early design misstep that we cannot get rid of for now. We will get rid of that when the new source interface lands ([1]) and when we have a new Kafka Source based on that.

As a workaround, we should change the Kafka Consumer to go through a different constructor of ListStateDescriptor which directly takes a TypeSerializer instead of a TypeInformation here: [2]. This should sidestep the "no generic types" check.

[1] https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface
[2] https://github.com/apache/flink/blob/68cc21e4af71505efa142110e35a1f8b1c25fe6e/flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaConsumerBase.java#L860

Issue Links

• duplicates: FLINK-12410 KafkaTopicPartition cannot be used as a POJO type because not all fields are valid POJO fields
• is related to: FLINK-11911 KafkaTopicPartition is not a valid POJO
• relates to: FLINK-11911 KafkaTopicPartition is not a valid POJO
• links to: GitHub Pull Request #11145