Failed to deserialize data for topic to avro sink connector - apache-kafka-connect

Question

i'm using confluent and connect rdbms to kafka, and it works.
some ETL with KSQL works to. But when i want to sink my stream/table back to rdbms, now there is a problem.
checking my topic/stream if there is avro :
./bin/kafka-avro-console-consumer --bootstrap-server localhost:9092 --property schema.registry.url=http://localhost:8081 --from-beginning --max-messages 1 --topic STR_VAHG_REKEY_02 | jq '.'
result:
{
"REKEY02": {
"long": 3941641584970777000
}
}
seems works fine, but when i sink it :
org.apache.kafka.connect.errors.ConnectException: Tolerance exceeded in error handler\n\
tat org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndHandleError(RetryWithToleranceOperator.java:178)\n\
tat org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execute(RetryWithToleranceOperator.java:104)\n\
tat org.apache.kafka.connect.runtime.WorkerSinkTask.convertAndTransformRecord(WorkerSinkTask.java:484)\n\
tat org.apache.kafka.connect.runtime.WorkerSinkTask.convertMessages(WorkerSinkTask.java:464)\n\
tat org.apache.kafka.connect.runtime.WorkerSinkTask.poll(WorkerSinkTask.java:320)\n\
tat org.apache.kafka.connect.runtime.WorkerSinkTask.iteration(WorkerSinkTask.java:224)\n\
tat org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:192)\n\
tat org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:177)\n\
tat org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:227)\n\
tat java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)\n\
tat java.util.concurrent.FutureTask.run(FutureTask.java:266)\n\
tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\
tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\
tat java.lang.Thread.run(Thread.java:748)\n
Caused by: org.apache.kafka.connect.errors.DataException: Failed to deserialize data for topic STR_VAHG_REKEY_02 to Avro: \n\
tat io.confluent.connect.avro.AvroConverter.toConnectData(AvroConverter.java:110)\n\
tat org.apache.kafka.connect.runtime.WorkerSinkTask.lambda$convertAndTransformRecord$0(WorkerSinkTask.java:484)\n\
tat org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndRetry(RetryWithToleranceOperator.java:128)\n\
tat org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndHandleError(RetryWithToleranceOperator.java:162)\n\t...
13 more\n
Caused by: org.apache.kafka.common.errors.SerializationException: Error deserializing Avro message for id -1\n
Caused by: org.apache.kafka.common.errors.SerializationException: Unknown magic byte!\n"
here is my sink file:
connector.class=io.confluent.connect.jdbc.JdbcSinkConnector
tasks.max=1
topics=STR_VAHG_REKEY_02
connection.url=jdbc:mysql://
connection.user=
connection.password=
auto.create=true
timestamp.column.name=create_at
validate.non.null=false
key.converter=io.confluent.connect.avro.AvroConverter
key.converter.schema.registry.url=http://localhost:8081
value.converter=io.confluent.connect.avro.AvroConverter
value.converter.schema.registry.url=http://localhost:8081
im lost already, any suggestion would be nice

Answer 1

Your avro-console-consumer output shows correctly that the value is Avro - but ksqlDB writes message keys as a string, not Avro.
Replace these two lines
key.converter=io.confluent.connect.avro.AvroConverter
key.converter.schema.registry.url=http://localhost:8081
with
key.converter=org.apache.kafka.connect.storage.StringConverter

Answer 2

I was also having the same issue. In my case, I was sending plain-text and AVRO messages on the same topic, so that's why consumer was not able to deserialize the data because the consumer was thinking to get only AVRO messages but it was receiving both(AVRO and normal messages).
How I fixed this: I deleted the topic and send only the AVRO messages and my issue got fixed.