[KAFKA-9969] ConnectorClientConfigRequest is loaded in isolation and throws LinkageError

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.5.0, 2.4.1
• Fix Version/s: 2.3.2, 2.6.0, 2.4.2, 2.5.1
• Component/s: connect
• Assignee: Greg Harris
• Reporter: Greg Harris
• Reviewer: Konstantine Karantasis
• Created: 07/May/20 19:50
• Updated: 11/Jun/20 15:12
• Resolved: 11/Jun/20 15:12

Description

ConnectorClientConfigRequest (added by KIP-458) is a class in connect-api, and should always be loaded by the system classloader. If a plugin packages the connect-api jar, the REST API may fail with the following stacktrace:

java.lang.LinkageError: loader constraint violation: loader (instance of sun/misc/Launcher$AppClassLoader) previously initiated loading for a different type with name "org/apache/kafka/connect/connector/policy/ConnectorClientConfigRequest" at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:763) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:468) at java.net.URLClassLoader.access$100(URLClassLoader.java:74) at java.net.URLClassLoader$1.run(URLClassLoader.java:369) at java.net.URLClassLoader$1.run(URLClassLoader.java:363) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:362) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at org.apache.kafka.connect.runtime.AbstractHerder.validateClientOverrides(AbstractHerder.java:416) at org.apache.kafka.connect.runtime.AbstractHerder.validateConnectorConfig(AbstractHerder.java:342) at org.apache.kafka.connect.runtime.distributed.DistributedHerder$6.call(DistributedHerder.java:745) at org.apache.kafka.connect.runtime.distributed.DistributedHerder$6.call(DistributedHerder.java:742) at org.apache.kafka.connect.runtime.distributed.DistributedHerder.tick(DistributedHerder.java:342) at org.apache.kafka.connect.runtime.distributed.DistributedHerder.run(DistributedHerder.java:282) at java.util.concurrent.Executors$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) ... 1 more

It appears that the other class in org.apache.kafka.connect.connector.policy, ConnectorClientConfigOverridePolicy had a similar issue in KAFKA-8415, and received a fix.

Issue Links

• links to: GitHub Pull Request #8630