[jira] [Created] (KAFKA-9537) Abstract transformations in configurations cause unfriendly error message.

["Jeremy Custenborder (Jira)" <ji...@apache.org>]

Jeremy Custenborder created KAFKA-9537:
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             Summary: Abstract transformations in configurations cause unfriendly error message.
                 Key: KAFKA-9537
                 URL: https://issues.apache.org/jira/browse/KAFKA-9537
             Project: Kafka
          Issue Type: Bug
          Components: KafkaConnect
    Affects Versions: 2.4.0
            Reporter: Jeremy Custenborder
            Assignee: Jeremy Custenborder


I was working with a coworker who had a bash script posting a config to connect with
{code:java}org.apache.kafka.connect.transforms.ExtractField.$Key{code} in the script. Bash removed the $Key because it wasn't escaped properly.
{code:java}
org.apache.kafka.connect.transforms.ExtractField.{code}
is made it to the rest interface. A Class<?> was create for the abstract implementation of ExtractField and passed to getConfigDefFromTransformation. It tried to call newInstance which threw an exception. The following gets returned via the rest interface. 

{code}
{
  "error_code": 400,
  "message": "Connector configuration is invalid and contains the following 1 error(s):\nInvalid value class org.apache.kafka.connect.transforms.ExtractField for configuration transforms.extractString.type: Error getting config definition from Transformation: null\nYou can also find the above list of errors at the endpoint `/{connectorType}/config/validate`"
}
{code}

It would be a much better user experience if we returned something like 
{code}
{
  "error_code": 400,
  "message": "Connector configuration is invalid and contains the following 1 error(s):\nInvalid value class org.apache.kafka.connect.transforms.ExtractField for configuration transforms.extractString.type: Error getting config definition from Transformation: Transformation is abstract and cannot be created.\nYou can also find the above list of errors at the endpoint `/{connectorType}/config/validate`"
}
{code}

or
{code}
{
  "error_code": 400,
  "message": "Connector configuration is invalid and contains the following 1 error(s):\nInvalid value class org.apache.kafka.connect.transforms.ExtractField for configuration transforms.extractString.type: Error getting config definition from Transformation: Transformation is abstract and cannot be created. Did you mean ExtractField$Key, ExtractField$Value?\nYou can also find the above list of errors at the endpoint `/{connectorType}/config/validate`"
}
{code}





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