Chris Egerton created KAFKA-13327:
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Summary: Preflight validations of connectors leads to 500 responses
Key: KAFKA-13327
URL: https://issues.apache.org/jira/browse/KAFKA-13327
Project: Kafka
Issue Type: Bug
Components: KafkaConnect
Reporter: Chris Egerton
Assignee: Chris Egerton
The Connect framework performs some preflight validations for all connectors
that are created in addition to allowing connectors to define their own custom
validation logic by providing a {{ConfigDef}} object in
[Connector::config|https://kafka.apache.org/30/javadoc/org/apache/kafka/connect/connector/Connector.html#config()]
and performing multi-property validation in
[Connector::validate|https://kafka.apache.org/30/javadoc/org/apache/kafka/connect/connector/Connector.html#validate(java.util.Map)].
When performed correctly, this validation information is surfaced to the user
in the form of a
[ConfigInfos|https://github.com/apache/kafka/blob/4eb386f6e060e12e1940c0d780987e3a7c438d74/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/entities/ConfigInfos.java]
object containing a list of [config
objects|https://github.com/apache/kafka/blob/4eb386f6e060e12e1940c0d780987e3a7c438d74/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/entities/ConfigInfo.java#L42-L45]
whose
[values|https://github.com/apache/kafka/blob/4eb386f6e060e12e1940c0d780987e3a7c438d74/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/entities/ConfigInfo.java#L42-L45]
contain one or more [error
messages|https://github.com/apache/kafka/blob/4eb386f6e060e12e1940c0d780987e3a7c438d74/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/entities/ConfigValueInfo.java#L61-L64].
This can be used as the response for a REST request to PUT
/connector-plugins/\{connectorType}/config/validate and allows programmatic UIs
to render error messages for every invalid property to the user.
However, some validations performed by the Connect framework do not follow this
pattern and instead result in a 500 response being returned to the user. For
example, logic specific to sink connectors (see
[AbstractHerder|https://github.com/apache/kafka/blob/4eb386f6e060e12e1940c0d780987e3a7c438d74/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L436]
and
[SinkConnectorConfig|https://github.com/apache/kafka/blob/4eb386f6e060e12e1940c0d780987e3a7c438d74/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/SinkConnectorConfig.java#L88-L125])
simply throws an exception instead of documenting the error with the offending
property and returning it in a standard response.
We should correct this logic wherever possible so that configurations that are
not fatally invalid (i.e., may have invalid properties but can still be
translated into a meaningful {{ConfigInfos}} response object) do not cause a
500 response to be returned to the user.
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