@Override
  public int hashCode() {
    int result = grouperFactoryClassName.hashCode();
    result = 31 * result + taskName.hashCode();
    result = 31 * result + type.hashCode();
    return result;
  }
Two {@link KafkaCheckpointLogKey}s are equal iff their grouperFactory class, taskName and type are equal.
samza-kafka/src/main/java/org/apache/samza/checkpoint/kafka/KafkaCheckpointLogKey.java