How do I configure spring-kafka to ignore messages in the wrong format?

Question

We have an issue with one of our Kafka topics which is consumed by the DefaultKafkaConsumerFactory & ConcurrentMessageListenerContainer combination described here with a JsonDeserializer used by the Factory. Unfortunately someone got a little enthusiastic and published some invalid messages onto the topic. It appears that spring-kafka silently fails to process past the first of these messages. Is it possible to have spring-kafka log an error and continue? Looking at the error messages which are logged it seems that perhaps the Apache kafka-clients library should deal with the case that when iterating a batch of messages one or more of them may fail to parse?

The below code is an example test case illustrating this issue:

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.common.serialization.Serializer;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.apache.kafka.common.serialization.StringSerializer;
import org.junit.ClassRule;
import org.junit.Test;
import org.springframework.kafka.core.DefaultKafkaConsumerFactory;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.listener.KafkaMessageListenerContainer;
import org.springframework.kafka.listener.MessageListener;
import org.springframework.kafka.listener.config.ContainerProperties;
import org.springframework.kafka.support.SendResult;
import org.springframework.kafka.support.serializer.JsonDeserializer;
import org.springframework.kafka.support.serializer.JsonSerializer;
import org.springframework.kafka.test.rule.KafkaEmbedded;
import org.springframework.kafka.test.utils.ContainerTestUtils;
import org.springframework.util.concurrent.ListenableFuture;

import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThat;
import static org.springframework.kafka.test.hamcrest.KafkaMatchers.hasKey;
import static org.springframework.kafka.test.hamcrest.KafkaMatchers.hasValue;

/**
 * @author jfreedman
 */
public class TestSpringKafka {
    private static final String TOPIC1 = "spring.kafka.1.t";

    @ClassRule
    public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, 1, TOPIC1);

    @Test
    public void submitMessageThenGarbageThenAnotherMessage() throws Exception {
        final BlockingQueue<ConsumerRecord<String, JsonObject>> records = createListener(TOPIC1);
        final KafkaTemplate<String, JsonObject> objectTemplate = createPublisher("json", new JsonSerializer<JsonObject>());

        sendAndVerifyMessage(records, objectTemplate, "foo", new JsonObject("foo"), 0L);

        // push some garbage text to Kafka which cannot be marshalled, this should not interrupt processing
        final KafkaTemplate<String, String> garbageTemplate = createPublisher("garbage", new StringSerializer());
        final SendResult<String, String> garbageResult = garbageTemplate.send(TOPIC1, "bar","bar").get(5, TimeUnit.SECONDS);
        assertEquals(1L, garbageResult.getRecordMetadata().offset());

        sendAndVerifyMessage(records, objectTemplate, "baz", new JsonObject("baz"), 2L);
    }

    private <T> KafkaTemplate<String, T> createPublisher(final String label, final Serializer<T> serializer) {
        final Map<String, Object> producerProps = new HashMap<>();
        producerProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, embeddedKafka.getBrokersAsString());
        producerProps.put(ProducerConfig.CLIENT_ID_CONFIG, "TestPublisher-" + label);
        producerProps.put(ProducerConfig.ACKS_CONFIG, "all");
        producerProps.put(ProducerConfig.RETRIES_CONFIG, 2);
        producerProps.put(ProducerConfig.MAX_IN_FLIGHT_REQUESTS_PER_CONNECTION, 1);
        producerProps.put(ProducerConfig.REQUEST_TIMEOUT_MS_CONFIG, 5000);
        producerProps.put(ProducerConfig.MAX_BLOCK_MS_CONFIG, 5000);
        producerProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
        producerProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, serializer.getClass());
        final DefaultKafkaProducerFactory<String, T> pf = new DefaultKafkaProducerFactory<>(producerProps);
        pf.setValueSerializer(serializer);
        return new KafkaTemplate<>(pf);
    }

    private BlockingQueue<ConsumerRecord<String, JsonObject>> createListener(final String topic) throws Exception {
        final Map<String, Object> consumerProps = new HashMap<>();
        consumerProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, embeddedKafka.getBrokersAsString());
        consumerProps.put(ConsumerConfig.GROUP_ID_CONFIG, "TestConsumer");
        consumerProps.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, true);
        consumerProps.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "100");
        consumerProps.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 15000);
        consumerProps.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        consumerProps.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, JsonDeserializer.class);
        final DefaultKafkaConsumerFactory<String, JsonObject> cf = new DefaultKafkaConsumerFactory<>(consumerProps);
        cf.setValueDeserializer(new JsonDeserializer<>(JsonObject.class));
        final KafkaMessageListenerContainer<String, JsonObject> container = new KafkaMessageListenerContainer<>(cf, new ContainerProperties(topic));
        final BlockingQueue<ConsumerRecord<String, JsonObject>> records = new LinkedBlockingQueue<>();
        container.setupMessageListener((MessageListener<String, JsonObject>) records::add);
        container.setBeanName("TestListener");
        container.start();
        ContainerTestUtils.waitForAssignment(container, embeddedKafka.getPartitionsPerTopic());
        return records;
    }

    private void sendAndVerifyMessage(final BlockingQueue<ConsumerRecord<String, JsonObject>> records,
                                      final KafkaTemplate<String, JsonObject> template,
                                      final String key, final JsonObject value,
                                      final long expectedOffset) throws InterruptedException, ExecutionException, TimeoutException {
        final ListenableFuture<SendResult<String, JsonObject>> future = template.send(TOPIC1, key, value);
        final ConsumerRecord<String, JsonObject> record = records.poll(5, TimeUnit.SECONDS);
        assertThat(record, hasKey(key));
        assertThat(record, hasValue(value));
        assertEquals(expectedOffset, future.get(5, TimeUnit.SECONDS).getRecordMetadata().offset());
    }

    public static final class JsonObject {
        private String value;

        public JsonObject() {}

        JsonObject(final String value) {
            this.value = value;
        }

        public String getValue() {
            return value;
        }

        public void setValue(final String value) {
            this.value = value;
        }

        @Override
        public boolean equals(final Object o) {
            if (this == o) { return true; }
            if (o == null || getClass() != o.getClass()) { return false; }
            final JsonObject that = (JsonObject) o;
            return Objects.equals(value, that.value);
        }

        @Override
        public int hashCode() {
            return Objects.hash(value);
        }

        @Override
        public String toString() {
            return "JsonObject{" +
                    "value='" + value + '\'' +
                    '}';
        }
    }
}

Answer 1

I have a solution but I don't know if it's the best one, I extended JsonDeserializer as follows which results in a null value being consumed by spring-kafka and requires the necessary downstream changes to handle that case.

class SafeJsonDeserializer[A >: Null](targetType: Class[A], objectMapper: ObjectMapper) extends JsonDeserializer[A](targetType, objectMapper) with Logging {
  override def deserialize(topic: String, data: Array[Byte]): A = try {
    super.deserialize(topic, data)
  } catch {
    case e: Exception =>
      logger.error("Failed to deserialize data [%s] from topic [%s]".format(new String(data), topic), e)
      null
  }
}