Hey Stevo, That's a good point. I think the javadoc is pretty clear that this could return no partitions when the consumer has no active assignment, but it may be a little unintuitive to have to call poll() after subscribing before you can get the assigned partitions. I can't think of a strong reason not to go ahead with the assignment in subscriptions() other than to keep it non-blocking. Perhaps you can open a ticket and we can get feedback from some other devs?
Thanks, Jason On Wed, Jul 22, 2015 at 2:09 AM, Stevo Slavić <ssla...@gmail.com> wrote: > Hello Apache Kafka community, > > In the new consumer I encountered unexpected behavior. After constructing > KafakConsumer instance with configured consumer rebalance callback handler, > and subscribing to a topic with "consumer.subscribe(topic)", retrieving > subscriptions would return empty set and callback handler would not get > called (no partitions ever assigned or revoked), no matter how long > instance was up. > > Then I found by inspecting KafkaConsumer code that partition assignment > will only be triggered on first poll, pollOnce has: > > // ensure we have partitions assigned if we expect to > if (subscriptions.partitionsAutoAssigned()) > coordinator.ensurePartitionAssignment(); > > Would it make sense to include this fragment in KafkaConsumer.subscriptions > accessor as well? > > Kind regards, > Stevo Slavic. >
