IllegalStateException Subscription to topics, partitions and pattern are mutually exclusive

Question

Need to fetch messages from a Kafka topic, from a particular offset

Stuck cause of IllegalStateException exception at assign()

If I do not use assign() , then the consumer does not perform seek, as that being a Lazy operation

Actual purpose: Need to iterate messages at topic from a pre-decided offset till end. This pre-decided offset is calculated at markOffset()

static void fetchMessagesFromMarkedOffset() {
    Consumer<Long, String> consumer = ConsumerCreator.createConsumer();
    consumer.assign(set); // <---- Exception at this place
    map.forEach((k,v) -> {
        consumer.seek(k, v-3);
    });
    ConsumerRecords<Long, String> consumerRecords = consumer.poll(100);
    consumerRecords.forEach(record -> {
        System.out.println("Record Key " + record.key());
        System.out.println("Record value " + record.value());
        System.out.println("Record partition " + record.partition());
        System.out.println("Record offset " + record.offset());
    });
    consumer.close();
}

Rest of concerned code involved

public static Set<TopicPartition> set;
public static Map<TopicPartition, Long> map;

static void markOffset() {
    Consumer<Long, String> consumer = ConsumerCreator.createConsumer();
    consumer.poll(100);
    set = consumer.assignment();
    map = consumer.endOffsets(set);
    System.out.println("Topic  Partitions: " + set);
    System.out.println("End Offsets: " + map);
}

Consumer Creation

private Consumer createConsumer(String topicName) {
    final Properties props = new Properties();
    props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
    props.put(ConsumerConfig.GROUP_ID_CONFIG, "capacity-service-application");
    props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, LongDeserializer.class.getName());
    props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
    props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "false");
    props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "latest");

    final Consumer consumer = new KafkaConsumer(props);
    consumer.subscribe(Collections.singletonList(topicName));
    return consumer;
}   

Exception

Exception in thread "main" java.lang.IllegalStateException: Subscription to topics, partitions and pattern are mutually exclusive
at org.apache.kafka.clients.consumer.internals.SubscriptionState.setSubscriptionType(SubscriptionState.java:104)
at org.apache.kafka.clients.consumer.internals.SubscriptionState.assignFromUser(SubscriptionState.java:157)
at org.apache.kafka.clients.consumer.KafkaConsumer.assign(KafkaConsumer.java:1064)
at com.gaurav.kafka.App.fetchMessagesFromMarkedOffset(App.java:44)
at com.gaurav.kafka.App.main(App.java:30)

Answer 1

You can't mixed manual and automatic partition assignment. You should use KafkaConsumer::subscribe or KafkaConsumer::assign but not both.

If after calling KafkaConsumer::subscribe you want to switch to manual approach you should first call KafkaConsumer::unsubscribe.

According to https://kafka.apache.org/10/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html

Note that it isn't possible to mix manual partition assignment (i.e. using assign) with dynamic partition assignment through topic subscription (i.e. using subscribe).