zentol commented on a change in pull request #15039:
URL: https://github.com/apache/flink/pull/15039#discussion_r590139866
##########
File path:
flink-runtime/src/test/java/org/apache/flink/runtime/metrics/util/MetricUtilsTest.java
##########
@@ -243,4 +240,59 @@ public MetricGroup addGroup(String name) {
METRIC_GROUP_MEMORY,
METRIC_GROUP_MANAGED_MEMORY)));
}
+
+ // --------------- utility methods and classes ---------------
+
+ /**
+ * An extreme simple class with no dependencies outside "java" package to
ease re-defining from
+ * its bytecode.
+ */
+ private static class Dummy {}
+
+ /**
+ * Define an new class using {@link Dummy} class's name and bytecode to
consume Metaspace and
+ * NonHeap memory.
+ */
+ @SuppressWarnings("unchecked")
+ private static Class<Dummy> redefineDummyClass() throws
ClassNotFoundException {
+ Class<?> clazz = Dummy.class;
+ ChildFirstClassLoader classLoader =
+ new ChildFirstClassLoader(
+ ClassLoaderUtils.getClasspathURLs(),
+ clazz.getClassLoader(),
+ new String[] {"java."},
+ ignored -> {});
+
+ Class<?> newClass = Class.forName(clazz.getName(), true, classLoader);
+
+ Assert.assertNotSame(clazz, newClass);
+ Assert.assertEquals(clazz.getName(), newClass.getName());
+ return (Class<Dummy>) newClass;
+ }
Review comment:
```suggestion
private static Class<?> redefineDummyClass() throws
ClassNotFoundException {
Class<?> clazz = Dummy.class;
ChildFirstClassLoader classLoader =
new ChildFirstClassLoader(
ClassLoaderUtils.getClasspathURLs(),
clazz.getClassLoader(),
new String[] {"java."},
ignored -> {});
Class<?> newClass = Class.forName(clazz.getName(), true,
classLoader);
Assert.assertNotSame(clazz, newClass);
Assert.assertEquals(clazz.getName(), newClass.getName());
return newClass;
}
```
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