Handling Common Errors | Kafka Object Serialization and Deserialization

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## Handling Common Errors

### 1. Serialization Exception
**Error:** `org.apache.kafka.common.errors.SerializationException: Can't convert value of class ... to class org.apache.kafka.common.serialization.StringSerializer specified in value.serializer`

**Cause:** This error occurs when Kafka expects a different serializer than the one provided. By default, Kafka uses `StringSerializer` for values.

**Solution:** Use the appropriate serializer for your custom objects. For example, if you are sending a JSON object, configure Kafka to use `JsonSerializer`.

**Code Snippet:**
```yaml
# application.yml for producer
spring:
  kafka:
    producer:
      key-serializer: org.apache.kafka.common.serialization.StringSerializer
      value-serializer: org.springframework.kafka.support.serializer.JsonSerializer

2. Deserialization Exception

Error: org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition ...

Cause: This error typically occurs when the consumer is unable to deserialize the message from the topic. This can happen if the deserializer does not match the serializer used by the producer.

Solution: Ensure that the consumer is using the correct deserializer.

Code Snippet:

# application.yml for consumer
spring:
  kafka:
    consumer:
      key-deserializer: org.apache.kafka.common.serialization.StringDeserializer
      value-deserializer: org.springframework.kafka.support.serializer.JsonDeserializer

3. Trusted Packages Exception

Error: java.lang.IllegalArgumentException: The class ... is not in the trusted packages

Cause: This error occurs when Kafka's deserializer does not trust the package of the serialized object.

Solution: Add the package to the trusted packages list in the consumer configuration.

Code Snippet:

# application.yml for consumer
spring:
  kafka:
    consumer:
      properties:
        spring.json.trusted.packages: 'com.example.package'

4. Missing Return Statement

Error: java.lang.Error: Missing return statement

Cause: This error occurs if a return statement is missing in a method that requires it.

Solution: Ensure that all methods have the necessary return statements.

Code Snippet:

public Map<String, Object> consumerConfigs() {
    Map<String, Object> props = new HashMap<>();
    // Add properties
    return props;
}

5. Consumer Group Rebalancing

Error: org.apache.kafka.clients.consumer.internals.AbstractCoordinator: [Consumer clientId=consumer-1, groupId=group-1] Attempt to join group failed due to ...

Cause: This error occurs when the consumer group is rebalancing, which can lead to temporary unavailability of consumers.

Solution: This is often a transient issue. Ensure your consumer is configured to handle rebalancing gracefully.

Code Snippet:

# application.yml for consumer
spring:
  kafka:
    consumer:
      enable-auto-commit: false
      auto-offset-reset: earliest

6. Producer Timeout Exception

Error: org.apache.kafka.common.errors.TimeoutException: Expiring ...

Cause: This error occurs when the producer is unable to send messages to the Kafka broker within the configured timeout.

Solution: Increase the timeout settings for the producer.

Code Snippet:

# application.yml for producer
spring:
  kafka:
    producer:
      properties:
        request.timeout.ms: 30000
        linger.ms: 5

For more information on setting up the project, visit Setting Up the Project. If you want to learn about creating and sending custom objects, check out Creating and Sending Custom Objects.


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