Github user tzulitai commented on a diff in the pull request: https://github.com/apache/flink/pull/2509#discussion_r101233499 --- Diff: flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/KafkaConsumerTestBase.java --- @@ -633,7 +654,12 @@ public void runStartFromGroupOffsets() throws Exception { readProps.setProperty("auto.offset.reset", "earliest"); // the committed group offsets should be used as starting points - KafkaTestEnvironment.KafkaOffsetHandler kafkaOffsetHandler = kafkaServer.createOffsetHandler(standardProps); + Properties offsetHandlerProps = new Properties(); + offsetHandlerProps.putAll(standardProps); + offsetHandlerProps.setProperty("key.deserializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer"); + offsetHandlerProps.setProperty("value.deserializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer"); --- End diff -- I didn't do that because the constructor of `KafkaOffsetHandlerImpl` has no knowledge of whether the provided `Properties` should be manipulated or not (users of `KafkaOffsetHandlerImpl` provide the properties). However, I think it would make sense to do what you suggested in the `KafkaOffsetHandlerImpl` if it always just uses `standardProps` instead of a provided properties. In our case that would be completely fine. I'll change it as proposed.
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