Joker-5 commented on code in PR #15642:
URL: https://github.com/apache/kafka/pull/15642#discussion_r1547690392
##########
connect/runtime/src/test/java/org/apache/kafka/connect/integration/ConnectorValidationIntegrationTest.java:
##########
@@ -69,6 +69,9 @@ public static void setup() {
Map<String, String> workerProps = new HashMap<>();
workerProps.put(GROUP_ID_CONFIG, WORKER_GROUP_ID);
+ // Work around a circular-dependency in TestPlugins.
+ TestPlugins.pluginPath();
Review Comment:
If we don't add this, methods which use `TestPlugins` will have erroneous
behavior. In particular:
```
[2024-04-02 19:16:25,977] ERROR Could not set up plugin test jars
(org.apache.kafka.connect.runtime.isolation.TestPlugins:258)
java.lang.NullPointerException
at
org.apache.kafka.connect.runtime.isolation.TestPlugins$TestPlugin.values(TestPlugins.java:69)
at
org.apache.kafka.connect.runtime.isolation.TestPlugins.<clinit>(TestPlugins.java:251)
at
org.apache.kafka.connect.runtime.isolation.TestPlugins$TestPlugin.<clinit>(TestPlugins.java:128)
at
org.apache.kafka.connect.integration.ConnectorValidationIntegrationTest.testConnectorHasConverterWithNoSuitableConstructor(ConnectorValidationIntegrationTest.java:337)
...
```
I found the reason behind it:
>TL;DR
The whole error occurred because the circle: inner class(some field depend
on outer class in the \<clinit> method) -> outer class(some line in static code
block depend on inner class in the \<clinit> method) -> inner class
1. There's a `private final Predicate<String> removeRuntimeClasses` field in
the inner class
`org.apache.kafka.connect.runtime.isolation.TestPlugins.TestPlugin`.
2. Some enums such as `BAD_PACKAGING_MISSING_SUPERCLASS` in (1)'s field will
depend on `private static final Predicate<String> REMOVE_CLASS_FILTER = s ->
s.contains("NonExistentInterface")` in the outer
class(`org.apache.kafka.connect.runtime.isolation.TestPlugins`).
3. When test mothod such as
`testConnectorHasConverterWithNoSuitableConstructor` is running, JVM will call
\<clinit> method to initialize the inner
class(`org.apache.kafka.connect.runtime.isolation.TestPlugins.TestPlugin`).
4. But some enum use the field(`removeRuntimeClasses`) in the outer
class(`private static final Predicate<String> REMOVE_CLASS_FILTER = s ->
s.contains("NonExistentInterface")`), so at that time JVM has to call \<clinit>
method to initialize the outer
class(`org.apache.kafka.connect.runtime.isolation.TestPlugins`).
5. In the outer class, there's a static code block which used the inner
class. But the inner class have not been initialized, the circular-dependency
just happened, which result in that error log.
```java
static {
Throwable err = null;
Map<String, Path> pluginJars = new HashMap<>();
try {
for (TestPlugin testPlugin : TestPlugin.values()) { // see this
line
if (pluginJars.containsKey(testPlugin.resourceDir())) {
log.debug("Skipping recompilation of " +
testPlugin.resourceDir());
}
pluginJars.put(testPlugin.resourceDir(),
createPluginJar(testPlugin.resourceDir(), testPlugin.removeRuntimeClasses()));
}
} catch (Throwable e) {
log.error("Could not set up plugin test jars", e);
err = e;
}
PLUGIN_JARS = Collections.unmodifiableMap(pluginJars);
INITIALIZATION_EXCEPTION = err;
}
```
So that's why I added the code.
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