[jira] [Assigned] (FLINK-20999) Confluent Avro Format should document how to serialize kafka keys

["Jark Wu (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-20999?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jark Wu reassigned FLINK-20999:
-------------------------------

    Assignee: Svend Vanderveken

> Confluent Avro Format should document how to serialize kafka keys
> -----------------------------------------------------------------
>
>                 Key: FLINK-20999
>                 URL: https://issues.apache.org/jira/browse/FLINK-20999
>             Project: Flink
>          Issue Type: Improvement
>          Components: Documentation, Table SQL / Ecosystem
>    Affects Versions: 1.12.0
>            Reporter: Svend Vanderveken
>            Assignee: Svend Vanderveken
>            Priority: Minor
>
> The [Confluent Avro Format|https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/connectors/formats/avro-confluent.html] only shows example of how to serialize/deserialize Kafka values. Also, parameter description is not always clear what is influencing the source and the sink behaviour, IMHO.
> This seems surprising especially in the context of a sink kafka connector since keys are such an important concept in that case.
> Adding examples of how to serialize/deserialize Kafka keys would add clarity.
> While it can be argued that a connector format is independent from the underlying storage, probably showing kafka-oriented examples in this case (i.e, with a concept of "key" and "value") makes senses here since this connector is very much thought with Kafka in mind.
>  
> I'm happy to submit a PR with all if this suggested change is approved?
>  
> I suggest to add this:
> h3. writing to Kafka while keeping the keys in "raw" big endian format:
> {code:java}
> CREATE TABLE OUTPUT_TABLE (
>   user_id BIGINT, 
>   item_id BIGINT, 
>   category_id BIGINT, 
>   behavior STRING
>  ) WITH (
>  'connector' = 'kafka',
>  'topic' = 'user_behavior',
>  'properties.bootstrap.servers' = 'localhost:9092',
>  'key.format' = 'raw',
>  'key.raw.endianness' = 'big-endian',
>  'key.fields' = 'user_id',
>  'value.format' = 'avro-confluent',
>  'value.avro-confluent.schema-registry.url' = 'http://localhost:8081',
>  'value.avro-confluent.schema-registry.subject' = 'user_behavior'
>  )
>  
> {code}
>  
> h3. writing to Kafka while registering both the key and the value to the schema registry
> {code:java}
> CREATE TABLE OUTPUT_TABLE (
>   user_id BIGINT, 
>   item_id BIGINT, 
>   category_id BIGINT, 
>   behavior STRING
>  ) WITH (
>  'connector' = 'kafka',
>  'topic' = 'user_behavior',
>  'properties.bootstrap.servers' = 'localhost:9092',
>  -- => this will register a {user_id: long} Avro type in the schema registry.
>  -- Watch out: schema evolution in the context of a Kafka key is almost never backward nor
>  -- forward compatible in practice due to hash partitioning.
>  'key.avro-confluent.schema-registry.url' = 'http://localhost:8081',
>  'key.avro-confluent.schema-registry.subject' = 'user_behavior_key',
>  'key.format' = 'avro-confluent',
>  'key.fields' = 'user_id',
>  'value.format' = 'avro-confluent',
>  'value.avro-confluent.schema-registry.url' = 'http://localhost:8081',
>  'value.avro-confluent.schema-registry.subject' = 'user_behavior_value'
>  )
>  
> {code}
>  
> h3. reading form Kafka with both the key and value schema in the registry while resolving field name clashes:
> {code:java}
> CREATE TABLE INPUT_TABLE (
>   -- user_id as read from the kafka key:
>   from_kafka_key_user_id BIGINT,
>  
>   -- user_id, and other fields, as read from the kafka value-
>   user_id BIGINT, 
>   item_id BIGINT, 
>   category_id BIGINT, 
>   behavior STRING
>  ) WITH (
>  'connector' = 'kafka',
>  'topic' = 'user_behavior',
>  'properties.bootstrap.servers' = 'localhost:9092',
>  'key.format' = 'avro-confluent',
>  'key.avro-confluent.schema-registry.url' = 'http://localhost:8081',
>  'key.fields' = 'from_kafka_key_user_id',
>  -- Adds a column prefix when mapping the avro fields of the kafka key to columns of this Table
>  -- to avoid clashes with avro fields of the value (both contain 'user_id' in this example)
>  'key.fields-prefix' = 'from_kafka_key_',
>  'value.format' = 'avro-confluent',
>  -- cannot include key here since dealt with above
>  'value.fields-include' = 'EXCEPT_KEY',
>  'value.avro-confluent.schema-registry.url' = 'http://localhost:8081'
>  )
>  
> {code}
>  
>  
>  



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