KafkaAvroSerializer for serializing Avro without schema.registry.url

Question

I\'m a noob to Kafka and Avro. So i have been trying to get the Producer/Consumer running. So far i have been able to produce and consume simple Bytes and Strings, using the fol

Answer 1

While the checked answer is all correct, it should also be mentioned that schema registration can be disabled.

Simply set auto.register.schemas to false.

Answer 2

You can always make your value classes to implement Serialiser<T>, Deserialiser<T> (and Serde<T> for Kafka Streams) manually. Java classes are usually generated from Avro files, so editing that directly isn't a good idea, but wrapping is maybe verbose but possible way.

Another way is to tune Arvo generator templates that are used for Java classes generation and generate implementation of all those interfaces automatically. Both Avro maven and gradle plugins supports custom templates, so it should be easy to configure.

I've created https://github.com/artemyarulin/avro-kafka-deserializable that has changed template files and simple CLI tool that you can use for file generation

Answer 3

As others have pointed out, KafkaAvroSerializer requires Schema Registry which is part of Confluent platform, and usage requires licensing.

The main advantage of using the schema registry is that your bytes on wire will smaller, as opposed to writing a binary payload with schema for every message.

I wrote a blog post detailing the advantages

Answer 4

Note first: KafkaAvroSerializer is not provided in vanilla apache kafka - it is provided by Confluent Platform. (https://www.confluent.io/), as part of its open source components (http://docs.confluent.io/current/platform.html#confluent-schema-registry)

Rapid answer: no, if you use KafkaAvroSerializer, you will need a schema registry. See some samples here: http://docs.confluent.io/current/schema-registry/docs/serializer-formatter.html

The basic idea with schema registry is that each topic will refer to an avro schema (ie, you will only be able to send data coherent with each other. But a schema can have multiple version, so you still need to identify the schema for each record)

We don't want to write the schema for everydata like you imply - often, schema is bigger than your data! That would be a waste of time parsing it everytime when reading, and a waste of ressources (network, disk, cpu)

Instead, a schema registry instance will do a binding avro schema <-> int schemaId and the serializer will then write only this id before the data, after getting it from registry (and caching it for later use).

So inside kafka, your record will be [<id> <bytesavro>] (and magic byte for technical reason), which is an overhead of only 5 bytes (to compare to the size of your schema) And when reading, your consumer will find the corresponding schema to the id, and deserializer avro bytes regarding it. You can find way more in confluent doc

If you really have a use where you want to write the schema for every record, you will need an other serializer (I think writing your own, but it will be easy, just reuse https://github.com/confluentinc/schema-registry/blob/master/avro-serializer/src/main/java/io/confluent/kafka/serializers/AbstractKafkaAvroSerializer.java and remove the schema registry part to replace it with the schema, same for reading). But if you use avro, I would really discourage this - one day a later, you will need to implement something like avro registry to manage versioning

Answer 5

You can create your Custom Avro serialiser, then even without Schema registry you would be able to produce records to topics. Check below article.

https://codenotfound.com/spring-kafka-apache-avro-serializer-deserializer-example.html

Here they have use Kafkatemplate . I have tried using

KafkaProducer<String, User> UserKafkaProducer

It is working fine But if you want to use KafkaAvroSerialiser, you need to give Schema registryURL