I increased partitions for one existing topic (2->10), but was surprised to see that it entirely reset the committed offsets of my consumer group.
All topics & partitions were reset to the earliest offset available, and the consumer read everything again. Documentation doesn't mention anything like this. Is this how it's supposed to work, or a bug? I would've expected the consumer offsets to not decrease at all, especially for the topics that I didn't even touch. For the altered topic I would've expected that consuming the previously existing partitions 0 and 1 would've continued from the position where they were, and naturally starting to read the new added partitions from 0. I added partitions according to the "Modifying topics" section of Kafka 0.10.0 Documentation: "To add partitions you can do > bin/kafka-topics.sh --zookeeper $ZOOKEEPER_HOST --alter --topic altered_topic --partitions 10 " Previously this topic had 2 partitions. For the consumer I'm using: kafka.javaapi.consumer.ConsumerConnector.createMessageStreamsByFilter() And version is: <groupId>org.apache.kafka</groupId> <artifactId>kafka_2.11</artifactId> <version>0.10.0.1</version> Kafka cluster itself is kafka_2.11-0.10.0.1.
