klaudworks opened a new issue, #515:
URL: https://github.com/apache/flink-agents/issues/515
## Summary
When `flink-agents-dist.jar` is deployed in `/opt/flink/lib` (which is
required), user-defined resource classes (e.g., custom `ChatModel`
implementations) cannot be loaded from user JARs uploaded via the REST API,
resulting in `ClassNotFoundException`.
## Error Message
```
java.lang.ClassNotFoundException: com.example.AzureOpenAIChatModelSetup
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown
Source)
at
java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown
Source)
at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Unknown Source)
at
org.apache.flink.agents.plan.resourceprovider.JavaResourceProvider.provide(JavaResourceProvider.java:40)
```
## Root Cause
The framework code in `/opt/flink/lib` is loaded by the **System
ClassLoader**. User JARs uploaded at runtime are loaded by Flink's **User
ClassLoader** (a child of the System ClassLoader).
The existing code uses `Class.forName(className)` which defaults to the
caller's classloader (System ClassLoader). Due to Java's parent-first
delegation model, the System ClassLoader cannot see classes in its child
classloaders.
Affected locations:
- `JavaResourceProvider.java` - main resource instantiation
- `JavaSerializableResourceProvider.java` - serializable resource
deserialization
- `AgentPlan.java` - PythonResourceWrapper class checks
- `ActionJsonDeserializer.java` - parameter type and config deserialization
- `FunctionToolJsonDeserializer.java` - parameter type deserialization
- `EventLogRecordJsonDeserializer.java` - event class deserialization
## Solution
Use the **Thread Context ClassLoader (TCCL)** instead:
```java
Class.forName(className, true,
Thread.currentThread().getContextClassLoader())
```
Flink sets the TCCL to the User ClassLoader before executing user code,
making user-defined classes accessible to framework code.
## Workaround
Place user-defined resource classes in `/opt/flink/lib` alongside
`flink-agents-dist.jar`. However, this is inconvenient for deployment scenarios
where the platform cannot anticipate what users will run (e.g., would require
rebuilding Docker images for each custom resource).
## Fix
PR #514
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