Hi ,
I am currently prototyping an Avro Apicurio format that I hope to raise as a
FLIP very soon (hopefully by early next week). In my prototyping , I am
passing through the Kafka headers content as a map to the DeserializationSchema
and have extended the SerializationSchema to pass back headers. I am using new
default methods in the interface so as to be backwardly compatible. I have the
deserialise working and the serialise is close.
We did consider trying to use the Apicurio deser libraries but this is tricky
due to the way the code is split.
Let me know what you think – I hope this approach will meet your needs,
Kind regards, David.
From: Balint Bene <balint.b...@shopify.com.INVALID>
Date: Tuesday, 12 March 2024 at 22:18
To: dev@flink.apache.org <dev@flink.apache.org>
Subject: [EXTERNAL] Additional metadata available for Kafka serdes
Hello! Looking to get some guidance for a problem around the Flink formats
used for Kafka.
Flink currently uses common serdes interfaces across all formats. However,
some data formats used in Kafka require headers for serdes. It's the same
problem for serialization and deserialization, so I'll just use
DynamicKafkaDeserialationSchema
<https://github.com/Shopify/shopify-flink-connector-kafka/blob/979791c4c71e944c16c51419cf9a84aa1f8fea4c/flink-connector-kafka/src/main/java/org/apache/flink/streaming/connectors/kafka/table/DynamicKafkaDeserializationSchema.java#L130
>
as
an example. It has access to the Kafka record headers, but it can't pass
them to the DeserializationSchema
<https://github.com/apache/flink/blob/94b55d1ae61257f21c7bb511660e7497f269abc7/flink-core/src/main/java/org/apache/flink/api/common/serialization/DeserializationSchema.java#L81
>
implemented
by the format since the interface is generic.
If it were possible to pass the headers, then open source formats such as
Apicurio could be supported. Unlike the Confluent formats which store the
metadata (schema ID) appended to the serialized bytes in the key and value,
the Apicurio formats store their metadata in the record headers.
I have bandwidth to work on this, but it would be great to have direction
from the community. I have a simple working prototype that's able to load a
custom version of the format with a modified interface that can accept the
headers (I just put the entire Apache Kafka ConsumerRecord
<https://kafka.apache.org/36/javadoc/org/apache/kafka/clients/consumer/ConsumerRecord.html
>
/ProducerRecord
<https://kafka.apache.org/36/javadoc/org/apache/kafka/clients/producer/ProducerRecord.html
>
for simplicity). The issues I foresee is that the class-loader
<https://github.com/apache/flink/blob/94b55d1ae61257f21c7bb511660e7497f269abc7/flink-core/src/main/java/org/apache/flink/core/classloading/ComponentClassLoader.java
>
exists in the Flink repo along with interfaces for the formats, but these
changes are specific to Kafka. This solution could require migrating
formats to the Flink-connector-kafka repo which is a decent amount of work.
Feedback is appreciated!
Thanks
Balint
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