Kafka Connect: How to extract a field - sql

Question

I'm using Debezium SQL Server Connector to stream a table into a topic. Thanks to Debezium's ExtractNewRecordState SMT, I'm getting the following message in my topic.
{
"schema":{
"type":"struct",
"fields":[
{
"type":"int64",
"optional":false,
"field":"id"
},
{
"type":"string",
"optional":false,
"field":"customer_code"
},
{
"type":"string",
"optional":false,
"field":"topic_name"
},
{
"type":"string",
"optional":true,
"field":"payload_key"
},
{
"type":"boolean",
"optional":false,
"field":"is_ordered"
},
{
"type":"string",
"optional":true,
"field":"headers"
},
{
"type":"string",
"optional":false,
"field":"payload"
},
{
"type":"int64",
"optional":false,
"name":"io.debezium.time.Timestamp",
"version":1,
"field":"created_on"
}
],
"optional":false,
"name":"test_server.dbo.kafka_event.Value"
},
"payload":{
"id":129,
"customer_code":"DVTPRDFT411",
"topic_name":"DVTPRDFT411",
"payload_key":null,
"is_ordered":false,
"headers":"{\"kafka_timestamp\":1594566354199}",
"payload":"MSG 18",
"created_on":1594595154267
}
}
After adding value.converter.schemas.enable=false, I could get rid of the schema portion and only the payload part is left as shown below.
{
"id":130,
"customer_code":"DVTPRDFT411",
"topic_name":"DVTPRDFT411",
"payload_key":null,
"is_ordered":false,
"headers":"{\"kafka_timestamp\":1594566354199}",
"payload":"MSG 19",
"created_on":1594595154280
}
I'd like to go 1 step further and extract only the customer_code field. I tried ExtractField$Value SMT but I keep getting the exception IllegalArgumentException: Unknown field: customer_code.
My configuration is as following
transforms=unwrap,extract
transforms.unwrap.type=io.debezium.transforms.ExtractNewRecordState
transforms.unwrap.drop.tombstones=true
transforms.unwrap.delete.handling.mode=drop
transforms.extract.type=org.apache.kafka.connect.transforms.ExtractField$Key
transforms.extract.field=customer_code
I tried a bunch of other SMTs including ExtractField$Key, ValueToKey but I couldn't make it work. I'd be very grateful if you could show me what I've done wrong. According to this tutorial from Confluent, it should work but it didn't.
** UPDATE **
I'm running Kafka Connect using connect-standalone worker.properties sqlserver.properties.
worker.properties
offset.storage.file.filename=C:/development/kafka_2.12-2.5.0/data/kafka/connect/connect.offsets
plugin.path=C:/development/kafka_2.12-2.5.0/plugins
bootstrap.servers=127.0.0.1:9092
offset.flush.interval.ms=10000
rest.port=10082
rest.host.name=127.0.0.1
rest.advertised.port=10082
rest.advertised.host.name=127.0.0.1
internal.key.converter=org.apache.kafka.connect.json.JsonConverter
internal.value.converter=org.apache.kafka.connect.json.JsonConverter
internal.key.converter.schemas.enable=false
internal.value.converter.schemas.enable=false
key.converter=org.apache.kafka.connect.json.JsonConverter
value.converter=org.apache.kafka.connect.json.JsonConverter
value.converter.schemas.enable=false
sqlserver.properties
name=sql-server-connector
connector.class=io.debezium.connector.sqlserver.SqlServerConnector
database.hostname=127.0.0.1
database.port=1433
database.user=sa
database.password=dummypassword
database.dbname=STGCTR
database.history.kafka.bootstrap.servers=127.0.0.1:9092
database.server.name=wfo
table.whitelist=dbo.kafka_event
database.history.kafka.topic=db_schema_history
transforms=unwrap,extract
transforms.unwrap.type=io.debezium.transforms.ExtractNewRecordState
transforms.unwrap.drop.tombstones=true
transforms.unwrap.delete.handling.mode=drop
transforms.extract.type=org.apache.kafka.connect.transforms.ExtractField$Value
transforms.extract.field=customer_code

Answer 1

The schema and payload fields sound like you're using data that was serialized with a JsonConverter with schemas enabled.
You can just set value.converter.schemas.enable=false to achieve your goal.