Kafka consumer group offset goes down to -1
The default offset retention policy offsets.retention.minutes used to be 1 day and in older Kafka versions the offset got wiped out even for active consumers. Fixed with KIP-211
We originally discovered this with Kafka 0.10.2.1, a few select topics lost the consumer group offsets (i.e., turned to -1) because no messages arrived on the topic for a couple of days and the offset retention policy kicked in and wiped out offsets for active consumers.
We were able to workaround this by increasing the retention setting to 7 days which seems to be what Kafka also ended up doing, see KIP-186