snehashisp commented on code in PR #16984:
URL: https://github.com/apache/kafka/pull/16984#discussion_r1873316820
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connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/Plugins.java:
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@@ -240,6 +261,21 @@ public Runnable withClassLoader(ClassLoader classLoader,
Runnable operation) {
};
}
+ public static LoaderSwap swapLoader(ClassLoader loader) {
Review Comment:
Actually, there are classloader swaps required in transformations as well. I
always wondered why separate plugins like connector and transformation, were
running under the connectors class loader in workertasks. I guess up until now
it would not cause issues as class loading would go via delegation to the
correct class loader. But with versioned plugins the delegation would end up on
the latest version of the plugin which can differ from the versioned plugin.
That was my reasoning for introducing loader swaps under converters and
transformations. The breath of places which required it led me to make it
static for easy access. Also, I did not unnecessarily want to inject the entire
plugin instance into those classes.
I think we would want to avoid the lookup cost of finding the classloader
from the plugins instance every time and then swapping the loader, so we would
need to maintain a set of extra class loader variables for each instance in the
worker tasks and transformations. I was thinking of exposing a `safeLoaderSwap`
java function like below and pass that on to the worker tasks and
transformations.
```
public Function<ClassLoader, LoaderSwap> safeLoaderSwapper() {
return loader -> {
if (!(loader instanceof PluginClassLoader)) {
loader = delegatingLoader;
}
return withClassLoader(loader);
};
}
```
That way we don't have to keep track of each class loader. wdyt?
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