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https://issues.apache.org/jira/browse/KAFKA-8407?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Randall Hauch resolved KAFKA-8407.
----------------------------------
Resolution: Fixed
Reviewer: Randall Hauch
Fix Version/s: 2.3.0
Merged onto the `trunk` and `2.3` branches.
> Connector client overrides broken on client configs with type 'Class' or
> 'List'
> -------------------------------------------------------------------------------
>
> Key: KAFKA-8407
> URL: https://issues.apache.org/jira/browse/KAFKA-8407
> Project: Kafka
> Issue Type: Bug
> Components: KafkaConnect
> Affects Versions: 2.3.0
> Reporter: Chris Egerton
> Assignee: Chris Egerton
> Priority: Blocker
> Labels: connect
> Fix For: 2.3.0
>
>
> When a connector request is submitted that overrides a client configuration
> that is meant to contain the name of a class (such as
> {{sasl.login.callback.handler.class}}), a 500 response is generated and the
> following stack trace can be found in the logs for Connect:
>
> {quote}[2019-05-22 14:51:36,123] ERROR Uncaught exception in REST call to
> /connectors
> (org.apache.kafka.connect.runtime.rest.errors.ConnectExceptionMapper:61)
> java.lang.ClassCastException: java.lang.String cannot be cast to
> java.lang.Class
> at
> org.apache.kafka.common.config.ConfigDef.convertToString(ConfigDef.java:774)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.convertConfigValue(AbstractHerder.java:491)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.validateClientOverrides(AbstractHerder.java:426)
> at
> org.apache.kafka.connect.runtime.AbstractHerder.validateConnectorConfig(AbstractHerder.java:342)
> at
> org.apache.kafka.connect.runtime.distributed.DistributedHerder$6.call(DistributedHerder.java:565)
> at
> org.apache.kafka.connect.runtime.distributed.DistributedHerder$6.call(DistributedHerder.java:562)
> at
> org.apache.kafka.connect.runtime.distributed.DistributedHerder.tick(DistributedHerder.java:292)
> at
> org.apache.kafka.connect.runtime.distributed.DistributedHerder.run(DistributedHerder.java:241)
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
> {quote}
> This appears to be limited only to client configs that are meant to be
> classes or lists due to the fact that {{ConfigDef.convertToString(...)}}
> assumes its first argument is an instance of {{Class<?>}} when its second
> argument is {{ConfigDef.Type.CLASS}} and then casts accordingly, and acts
> similarly for lists. If the second argument is anything else, {{toString()}}
> is invoked on it without any casting, avoiding any problems.
>
> The cause of this is due to the fact that the newly-introduced
> {{ConnectorClientConfigOverridePolicy}} interface returns a list of
> {{ConfigValue}} instances for its validation. The {{value()}} for each of
> these can be any type, although with the default implementations available
> ({{All}}, {{None}}, {{Principal}}) if one is returned at all it's just the
> same type of what was passed in for that particular config. In the case of
> the {{AbstractHerder.validateClientOverrides(...)}} method, the raw strings
> for the client configs are used. However, the
> {{AbstractHerder.convertConfigValue(...)}} is then called for those raw
> strings but with the {{ConfigDef.Type}} of the config based on the relevant
> client {{ConfigDef}} (i.e., {{ProducerConfig.configDef()}},
> {{ConsumerConfig.configDef()}}, or {{AdminClientConfig.configDef()}}). This
> in turn can and will result in
> {{ConfigDef.convertToString(someClassNameAsAString, ConfigDef.Type.CLASS)}}
> being invoked.
>
> Although this isn't technically a comprehensive fix, a quick option would be
> to invoke {{ConfigDef.parse(...)}} using the relevant client {{ConfigDef}}
> before passing overrides to the policy. Technically, this would still lead to
> problems if the policy decided to return just the name of a class for a
> config that of type class instead, so we may want to investigate other
> options as well.
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