How to handle exception while parsing JSON in Flink

Question

I am reading data from Kafka using flink 1.4.2 and parsing them to ObjectNode using JSONDeserializationSchema. If the incoming record is not a valid JSON then my Flink job fails. I would like to skip the broken record instead of failing the job.

FlinkKafkaConsumer010<ObjectNode> kafkaConsumer =
                new FlinkKafkaConsumer010<>(TOPIC, new JSONDeserializationSchema(), consumerProperties);
DataStream<ObjectNode> messageStream = env.addSource(kafkaConsumer);
messageStream.print();

I am getting the following exception if the data in Kafka is not a valid JSON.

Job execution switched to status FAILING.
org.apache.flink.shaded.jackson2.com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'This': was expecting ('true', 'false' or 'null')
 at [Source: [B@4f522623; line: 1, column: 6]
Job execution switched to status FAILED.
Exception in thread "main" org.apache.flink.runtime.client.JobExecutionException: Job execution failed.

Answer 1

As suggested by @twalthr, I implemented my own DeserializationSchema by copying JSONDeserializationSchema and added exception handling.

import org.apache.flink.api.common.serialization.AbstractDeserializationSchema;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.node.ObjectNode;
import java.io.IOException;

public class CustomJSONDeserializationSchema extends AbstractDeserializationSchema<ObjectNode> {

    private ObjectMapper mapper;

    @Override
    public ObjectNode deserialize(byte[] message) throws IOException {
        if (mapper == null) {
            mapper = new ObjectMapper();
        }

        ObjectNode objectNode;
        try {
            objectNode = mapper.readValue(message, ObjectNode.class);
        } catch (Exception e) {
            ObjectMapper errorMapper = new ObjectMapper();
            ObjectNode errorObjectNode = errorMapper.createObjectNode();
            errorObjectNode.put("jsonParseError", new String(message));
            objectNode = errorObjectNode;
        }
        return objectNode;
    }

    @Override
    public boolean isEndOfStream(ObjectNode nextElement) {
        return false;
    }

}

In my streaming job.

messageStream
        .filter((event) -> {
            if(event.has("jsonParseError")) {
                LOG.warn("JsonParseException was handled: " + event.get("jsonParseError").asText());
                return false;
            }
            return true;
        }).print();