Consumer does not read messages from the Kafka topic (Akka Stream Kafka)

We use Akka Stream Kafka for producing and consuming messages and Strimzi Kafka cluster. Here are the versions if matters:

com.typesafe.akka:akka-stream-kafka_2.13:2.0.7
  com.typesafe.akka:akka-stream_2.13:2.6.14
  org.apache.kafka:kafka-clients:2.4.1 (*)
  org.scala-lang.modules:scala-collection-compat_2.13:2.1.6
  org.scala-lang:scala-library:2.13.5

After a refactoring message consumer stopped working. We do have messages in the topic, but consumer just waits endlessly.

Here is the log fragment:

[2021-04-14 21:20:43,869] [INFO] [org.apache.kafka.common.utils.AppInfoParser] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-8] - Kafka version: 2.4.1
[2021-04-14 21:20:43,869] [INFO] [org.apache.kafka.common.utils.AppInfoParser] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-8] - Kafka commitId: c57222ae8cd7866b
[2021-04-14 21:20:43,869] [INFO] [org.apache.kafka.common.utils.AppInfoParser] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-8] - Kafka startTimeMs: 1618424443866
[2021-04-14 21:20:43,879] [INFO] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-8] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Subscribed to topic(s): xyz-abc-import-dev-abc-input-topic
[2021-04-14 21:20:45,907] [INFO] [org.apache.kafka.clients.Metadata] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-19] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Cluster ID: L9OdIPABTGa7V9OPdViAaw
[2021-04-14 21:20:45,973] [INFO] [org.apache.kafka.clients.consumer.internals.AbstractCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-21] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Discovered group coordinator kafka-staging-abc-cluster-kafka-0-kafka-abc.xyzabccluster-host:443 (id: 2147483647 rack: null)
[2021-04-14 21:20:46,245] [INFO] [org.apache.kafka.clients.consumer.internals.AbstractCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-21] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] (Re-)joining group
[2021-04-14 21:20:47,554] [INFO] [org.apache.kafka.clients.consumer.internals.AbstractCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-9] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] (Re-)joining group
[2021-04-14 21:20:50,780] [INFO] [org.apache.kafka.clients.consumer.internals.ConsumerCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-22] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Finished assignment for group at generation 5: {consumer-xyz-abc-import-1-995fd3d7-24b5-480d-90bc-b0967f0898f0=Assignment(partitions=[xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1])}
[2021-04-14 21:20:51,114] [INFO] [org.apache.kafka.clients.consumer.internals.AbstractCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-16] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Successfully joined group with generation 5
[2021-04-14 21:20:51,125] [INFO] [org.apache.kafka.clients.consumer.internals.ConsumerCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-16] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Adding newly assigned partitions: xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1
[2021-04-14 21:20:51,334] [INFO] [org.apache.kafka.clients.consumer.internals.ConsumerCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-18] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Setting offset for partition xyz-abc-import-dev-abc-input-topic-0 to the committed offset FetchPosition{offset=38, offsetEpoch=Optional.empty, currentLeader=LeaderAndEpoch{leader=kafka-staging-abc-cluster-kafka-0-kafka-abc.xyzabccluster-host:443 (id: 0 rack: null), epoch=0}}
[2021-04-14 21:20:51,336] [INFO] [org.apache.kafka.clients.consumer.internals.ConsumerCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-18] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Setting offset for partition xyz-abc-import-dev-abc-input-topic-1 to the committed offset FetchPosition{offset=51, offsetEpoch=Optional[0], currentLeader=LeaderAndEpoch{leader=kafka-staging-abc-cluster-kafka-1-kafka-abc.xyzabccluster-host:443 (id: 1 rack: null), epoch=0}}

Some more points:

1. Schema registry properly configured and good (otherwise producer would not work).
2. Topic (and group coordinator) is good, I can consume messages via plain consumer like that:

KafkaConsumer<String, MyMsg> consumer = new KafkaConsumer<String, MyMsg>(props);
consumer.subscribe(Collections.singletonList(inputTopic), rebalanceListener);
ConsumerRecords<String, MyMsg> records = consumer.poll(Duration.of(60L, ChronoUnit.SECONDS));

3. I use “earliest” reset config property, so it should see unconsumed messages.
4. This is what I have in the topic when I run – in partition 1 I have messages at offset 51 and 52, and consumer coordinator set to offset 51 in log, so the message is there (in fact, it must read 2 messages I produced for this testing)

This is the place where the code stuck — I use blocking call to get 2 messages (and cannot get even 1)

final Source<ProducerMessage.Results<String, Object, ConsumerMessage.PartitionOffset>, NotUsed> stream = ...
stream.take(SUBMISSION_SIZE).runWith(Sink.ignore(), mat).toCompletableFuture().get();

Not really sure how to debug it. 8-(

[UPD 1]

Can it relate somehow to transactions? Bacause plain Akka Stream Consumer can see the messages and consume:

    @Test
    @Order(3)
    void exploreTopic() throws IOException, ExecutionException, InterruptedException {
        Consumer.DrainingControl<java.util.List<ConsumerRecord<String, Object>>> controlCompletionStagePair =
            Consumer.plainSource(consumerSettings, Subscriptions.topics(inputTopic))
                .take(SUBMISSION_SIZE)
                .map(x -> {
                    System.out.println(x);
                    return x;
                })
                .toMat(Sink.seq(), Consumer::createDrainingControl)
                .run(mat);
        controlCompletionStagePair.streamCompletion().toCompletableFuture().get();
        System.out.println("xxx");
    }

[UPD 2]

I turned on DEBUG level of logging and see my partitions are placed on pause:

[2021-04-14 23:46:05,122] [DEBUG] [org.apache.kafka.clients.consumer.internals.Fetcher] [kafka-coordinator-heartbeat-thread | xyz-abc-import] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Fetch READ_COMMITTED at offset 40 for partition xyz-abc-import-dev-abc-input-topic-0 returned fetch data (error=NONE, highWaterMark=40, lastStableOffset = 40, logStartOffset = 40, preferredReadReplica = absent, abortedTransactions = [], recordsSizeInBytes=0)
[2021-04-14 23:46:05,725] [DEBUG] [org.apache.kafka.clients.consumer.internals.Fetcher] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-6] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Added READ_COMMITTED fetch request for partition xyz-abc-import-dev-abc-input-topic-0 at position FetchPosition{offset=40, offsetEpoch=Optional.empty, currentLeader=LeaderAndEpoch{leader=kafka-staging-abc-cluster-kafka-0-kafka-abc.xyzabccluster-host:443 (id: 0 rack: null), epoch=0}} to node kafka-staging-abc-cluster-kafka-0-kafka-abc.xyzabccluster-host:443 (id: 0 rack: null)
[2021-04-14 23:46:05,725] [DEBUG] [org.apache.kafka.clients.consumer.internals.Fetcher] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-6] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Added READ_COMMITTED fetch request for partition xyz-abc-import-dev-abc-input-topic-1 at position FetchPosition{offset=61, offsetEpoch=Optional[0], currentLeader=LeaderAndEpoch{leader=kafka-staging-abc-cluster-kafka-1-kafka-abc.xyzabccluster-host:443 (id: 1 rack: null), epoch=0}} to node kafka-staging-abc-cluster-kafka-1-kafka-abc.xyzabccluster-host:443 (id: 1 rack: null)
[2021-04-14 23:46:05,725] [DEBUG] [org.apache.kafka.clients.FetchSessionHandler] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-6] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Built incremental fetch (sessionId=339828876, epoch=1) for node 0. Added 0 partition(s), altered 0 partition(s), removed 0 partition(s) out of 1 partition(s)
[2021-04-14 23:46:05,725] [DEBUG] [org.apache.kafka.clients.FetchSessionHandler] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-6] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Built incremental fetch (sessionId=23429972, epoch=1) for node 1. Added 0 partition(s), altered 1 partition(s), removed 0 partition(s) out of 1 partition(s)
[2021-04-14 23:46:05,725] [DEBUG] [org.apache.kafka.clients.consumer.internals.Fetcher] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-6] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Sending READ_COMMITTED IncrementalFetchRequest(toSend=(), toForget=(), implied=(xyz-abc-import-dev-abc-input-topic-0)) to broker kafka-staging-abc-cluster-kafka-0-kafka-abc.xyzabccluster-host:443 (id: 0 rack: null)
[2021-04-14 23:46:05,726] [DEBUG] [org.apache.kafka.clients.consumer.internals.Fetcher] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-6] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Sending READ_COMMITTED IncrementalFetchRequest(toSend=(xyz-abc-import-dev-abc-input-topic-1), toForget=(), implied=()) to broker kafka-staging-abc-cluster-kafka-1-kafka-abc.xyzabccluster-host:443 (id: 1 rack: null)
[2021-04-14 23:46:05,796] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-7] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:05,866] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-10] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:05,935] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-11] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,009] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-13] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,075] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-15] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,149] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-18] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,215] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-20] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,288] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-21] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,355] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-8] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,355] [DEBUG] [org.apache.kafka.clients.consumer.internals.AbstractCoordinator] [kafka-coordinator-heartbeat-thread | xyz-abc-import] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Sending Heartbeat request to coordinator kafka-staging-abc-cluster-kafka-0-kafka-abc.xyzabccluster-host:443 (id: 2147483647 rack: null)
[2021-04-14 23:46:06,427] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-9] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,459] [DEBUG] [org.apache.kafka.clients.FetchSessionHandler] [kafka-coordinator-heartbeat-thread | xyz-abc-import] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Node 1 sent an incremental fetch response for session 23429972 with 0 response partition(s), 1 implied partition(s)
[2021-04-14 23:46:06,459] [DEBUG] [org.apache.kafka.clients.FetchSessionHandler] [kafka-coordinator-heartbeat-thread | xyz-abc-import] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Node 0 sent an incremental fetch response for session 339828876 with 0 response partition(s), 1 implied partition(s)
[2021-04-14 23:46:06,500] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-12] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,557] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-14] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,559] [DEBUG] [org.apache.kafka.clients.consumer.internals.AbstractCoordinator] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-14] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Received successful Heartbeat response
[2021-04-14 23:46:06,625] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-16] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,697] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-17] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]
[2021-04-14 23:46:06,765] [DEBUG] [org.apache.kafka.clients.consumer.KafkaConsumer] [SchemaRegistrySerializationTest-akka.kafka.default-dispatcher-19] - [Consumer clientId=consumer-xyz-abc-import-1, groupId=xyz-abc-import] Pausing partitions [xyz-abc-import-dev-abc-input-topic-0, xyz-abc-import-dev-abc-input-topic-1]

[UPD 3] Does it have to do with auto created topics?

Answer

It’s hard to tell how it impacts, but consumer started working properly once I added this property to consumer:

props.put(AvroDatumProvider.REGISTRY_USE_SPECIFIC_AVRO_READER_CONFIG_PARAM, String.valueOf(Boolean.TRUE));

Now sure what was the real cause, and why there was no error thrown, but adding property above helped, at least in my case.