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Evolving an Avro Schema in a Kafka Application

Confluent Schema Registry is a useful tool for coordinating contracts between producers and consumers, as well as simplifies the process of serializing and deserializing complex data objects. However, it also provides some powerful functionality to help you manage changes to your data schemas. In this lab, you will have the opportunity to make a change to an existing schema by adding a new field. This will give you some hands-on experience with the process of evolving a schema using the Confluent Schema Registry.

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Path Info

Level

Intermediate

Duration

30m

Published

Oct 18, 2019

Challenge

Clone the Starter Project and Run It to Make Sure Everything Is Working
1. Clone the starter project into your home directory:
```
cd ~/
git clone https://github.com/linuxacademy/content-ccdak-schema-evolve-lab.git
```
1. Run the code to ensure it works before modifying it:
```
cd content-ccdak-schema-evolve-lab
./gradlew runProducer
./gradlew runConsumer
```
Note: The consumer should output some records that were created by the producer.

Challenge

Update the Purchase Schema to Add the `member_id` Field

Edit the schema definition file:

vi src/main/avro/com/linuxacademy/ccdak/schemaregistry/Purchase.avsc

Add the member_id field with a blank default:

{
  "namespace": "com.linuxacademy.ccdak.schemaregistry",
  "compatibility": "FORWARD",
  "type": "record",
  "name": "Purchase",
  "fields": [
    {"name": "id", "type": "int"},
    {"name": "product", "type": "string"},
    {"name": "quantity", "type": "int"},
    {"name": "member_id", "type": "int", "default": 0}
  ]
}

Challenge

Update the Producer to Set the `member_id` for the Records It Publishes

Edit the schema definition file:

vi src/main/avro/com/linuxacademy/ccdak/schemaregistry/Purchase.avsc

Add the member_id field with a blank default:

{
  "namespace": "com.linuxacademy.ccdak.schemaregistry",
  "compatibility": "FORWARD",
  "type": "record",
  "name": "Purchase",
  "fields": [
    {"name": "id", "type": "int"},
    {"name": "product", "type": "string"},
    {"name": "quantity", "type": "int"},
    {"name": "member_id", "type": "int", "default": 0}
  ]
}

Update the Producer to Set the `member_id` for the Records It Publishes

Edit the producer Main class:

vi src/main/java/com/linuxacademy/ccdak/schemaregistry/ProducerMain.java

Implement the new member_id field in the producer by setting it for the records being produced:

package com.linuxacademy.ccdak.schemaregistry;

import io.confluent.kafka.serializers.AbstractKafkaAvroSerDeConfig;
import io.confluent.kafka.serializers.KafkaAvroSerializer;
import java.util.Properties;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.serialization.StringSerializer;

public class ProducerMain {

    public static void main(String[] args) {
        final Properties props = new Properties();
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
        props.put(ProducerConfig.ACKS_CONFIG, "all");
        props.put(ProducerConfig.RETRIES_CONFIG, 0);
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, KafkaAvroSerializer.class);
        props.put(AbstractKafkaAvroSerDeConfig.SCHEMA_REGISTRY_URL_CONFIG, "http://localhost:8081");

        KafkaProducer<String, Purchase> producer = new KafkaProducer<String, Purchase>(props);

        Purchase apples = new Purchase(1, "apples", 17, 77543);
        producer.send(new ProducerRecord<String, Purchase>("inventory_purchases", apples.getId().toString(), apples));

        Purchase oranges = new Purchase(2, "oranges", 5, 56878);
        producer.send(new ProducerRecord<String, Purchase>("inventory_purchases", oranges.getId().toString(), oranges));

        producer.close();
    }

}

Run the producer:

./gradlew runProducer

Run the consumer:

./gradlew runConsumer

Verify the data in the output file. We should see the new member_id data in the last lines of the file:

cat /home/cloud_user/output/output.txt

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

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