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https://issues.apache.org/jira/browse/KAFKA-9845?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Randall Hauch resolved KAFKA-9845.
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Fix Version/s: 2.7.0
Reviewer: Randall Hauch
Resolution: Fixed
Merged to `trunk`, and backported to `2.6` (for upcoming 2.6.0), `2.5` (for
upcoming 2.5.1), and `2.4` (for future 2.4.2).
> plugin.path property does not work with config provider
> -------------------------------------------------------
>
> Key: KAFKA-9845
> URL: https://issues.apache.org/jira/browse/KAFKA-9845
> Project: Kafka
> Issue Type: Bug
> Components: KafkaConnect
> Affects Versions: 2.3.0, 2.4.0, 2.3.1, 2.5.0, 2.4.1
> Reporter: Chris Egerton
> Assignee: Chris Egerton
> Priority: Minor
> Fix For: 2.6.0, 2.4.2, 2.5.1, 2.7.0
>
>
> The config provider mechanism doesn't work if used for the {{plugin.path}}
> property of a standalone or distributed Connect worker. This is because the
> {{Plugins}} instance which performs plugin path scanning is created using the
> raw worker config, pre-transformation (see
> [ConnectStandalone|https://github.com/apache/kafka/blob/371ad143a6bb973927c89c0788d048a17ebac91a/connect/runtime/src/main/java/org/apache/kafka/connect/cli/ConnectStandalone.java#L79]
> and
> [ConnectDistributed|https://github.com/apache/kafka/blob/371ad143a6bb973927c89c0788d048a17ebac91a/connect/runtime/src/main/java/org/apache/kafka/connect/cli/ConnectDistributed.java#L91]).
> Unfortunately, because config providers are loaded as plugins, there's a
> circular dependency issue here. The {{Plugins}} instance needs to be created
> _before_ the {{DistributedConfig}}/{{StandaloneConfig}} is created in order
> for the config providers to be loaded correctly, and the config providers
> need to be loaded in order to perform their logic on any properties
> (including the {{plugin.path}} property).
> There is no clear fix for this issue in the code base, and the only known
> workaround is to refrain from using config providers for the {{plugin.path}}
> property.
> A couple improvements could potentially be made to improve the UX when this
> issue arises:
> # Alter the config logging performed by the {{DistributedConfig}} and
> {{StandaloneConfig}} classes to _always_ log the raw value for the
> {{plugin.path}} property. Right now, the transformed value is logged even
> though it isn't used, which is likely to cause confusion.
> # Issue a {{WARN}}- or even {{ERROR}}-level log message when it's detected
> that the user is attempting to use config providers for the {{plugin.path}}
> property, which states that config providers cannot be used for that specific
> property, instructs them to change the value for the property accordingly,
> and/or informs them of the actual value that the framework will use for that
> property when performing plugin path scanning.
> We should _not_ throw an error on startup if this condition is detected, as
> this could cause previously-functioning, benignly-misconfigured Connect
> workers to fail to start after an upgrade.
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