boolean updateAssignmentMetadataIfNeeded(final Timer timer, final boolean waitForJoinGroup) {
        if (coordinator != null && !coordinator.poll(timer, waitForJoinGroup)) {
            return false;
        }

        return updateFetchPositions(timer);
    }
@throws KafkaException if the rebalance callback throws exception
clients/src/main/java/org/apache/kafka/clients/consumer/internals/ClassicKafkaConsumer.java