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https://issues.apache.org/jira/browse/KAFKA-18211?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17904941#comment-17904941
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Greg Harris commented on KAFKA-18211:
-------------------------------------
This is a regression in plugin discovery behavior after the change to the
Classgraph library, which has not been released yet. It must be fixed before
the upcoming release.
> ClassGraph scanning does not correctly find isolated connect plugins
> --------------------------------------------------------------------
>
> Key: KAFKA-18211
> URL: https://issues.apache.org/jira/browse/KAFKA-18211
> Project: Kafka
> Issue Type: Bug
> Components: connect
> Affects Versions: 4.0.0
> Reporter: Snehashis Pal
> Priority: Blocker
> Fix For: 4.0.0
>
>
> Connect used to use reflections scanner for scanning and identifying connect
> plugins in its plugin.path. This would load said plugins in isolation via the
> use of a child first PluginClassloader, which is designed to load class from
> its set of URIs before delegating to parent, if not found. This effectively
> enforces that if a plugin and its dependencies are part of a plugin path it
> would not conflict with other plugins in the plugin path or plugins in
> classpath.
>
> GlassGraph was introduced as a replacement for the older reflections scanner
> in [KAFKA-15203 Use Classgraph since org.reflections is no longer under
> maintainence by PARADOXST · Pull Request #16604 ·
> apache/kafka|https://github.com/apache/kafka/pull/16604]. It is used in place
> of reflections scanner for finding plugins during plugin scanning. The issue
> here is that it is missing any plugins present in isolated plugin paths if
> its already present in classpath. We can repro this by adding the json
> converter under an isolated plugin path and starting connect with debug logs.
> We can see the logs from ReflectionsScanner and find that the ClassGraph
> loader is always fetching the plugin from the classpath even though the
> PluginClassLoader is provided. This is causing
> [kafka/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/ReflectionScanner.java
> at 520681c38dbefe497181c4fd5dfc793d54233408 ·
> apache/kafka|https://github.com/apache/kafka/blob/520681c38dbefe497181c4fd5dfc793d54233408/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/ReflectionScanner.java#L134]
> check to fail with the logs like.
> {code:java}
> [2024-12-11 07:29:28,968] DEBUG class
> org.apache.kafka.connect.json.JsonConverter from other classloader
> jdk.internal.loader.ClassLoaders$AppClassLoader@c387f44 is visible from
> C:\Users\user\Desktop\confluent\testing\plugins3\connect-file-1.2.1-T-0.9.0-P-3.1,
> excluding to prevent isolated loading
> (org.apache.kafka.connect.runtime.isolation.ReflectionScanner:135)
> [2024-12-11 07:29:28,969] DEBUG class
> org.apache.kafka.connect.json.JsonConverter from other classloader
> jdk.internal.loader.ClassLoaders$AppClassLoader@c387f44 is visible from
> C:\Users\user\Desktop\confluent\testing\plugins3\connect-file-1.2.1-T-0.9.0-P-3.1,
> excluding to prevent isolated loading
> (org.apache.kafka.connect.runtime.isolation.ReflectionScanner:135) {code}
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