AHeise commented on a change in pull request #11303: [FLINK-16245] Decoupling
user classloader from context classloader.
URL: https://github.com/apache/flink/pull/11303#discussion_r393553966
##########
File path:
flink-runtime/src/main/java/org/apache/flink/runtime/execution/librarycache/FlinkUserCodeClassLoaders.java
##########
@@ -82,4 +89,61 @@ public static ResolveOrder fromString(String resolveOrder) {
super(urls, parent);
}
}
+
+ /**
+ * Ensures that holding a reference on the context class loader
outliving the scope of user code does not prevent
+ * the user classloader to be garbage collected (FLINK-16245).
+ *
+ * <p>This classloader delegates to the actual user classloader. Upon
{@link #close()}, the delegate is nulled
+ * and can be garbage collected. Additional class resolution will be
resolved solely through the bootstrap
+ * classloader and most likely result in ClassNotFound exceptions.
+ */
+ private static class SafetyNetWrapperClassLoader extends URLClassLoader
+ implements Closeable {
+ private static final Logger LOG =
LoggerFactory.getLogger(SafetyNetWrapperClassLoader.class);
+
+ private FlinkUserCodeClassLoader inner;
+
+ SafetyNetWrapperClassLoader(FlinkUserCodeClassLoader inner) {
+ super(new URL[0], null);
+ this.inner = inner;
+ }
+
+ @Override
+ public void close() {
+ if (inner != null) {
+ try {
+ inner.close();
+ } catch (IOException e) {
+ LOG.warn("Could not close user
classloader", e);
+ }
+ }
+ inner = null;
+ }
+
+ @Override
+ protected Class<?> loadClass(String name, boolean resolve)
throws ClassNotFoundException {
+ if (inner == null) {
+ return super.loadClass(name, resolve);
Review comment:
> Given that the CL is only closed when all tasks on the TE have stopped,
how could it affect a job? Leftover threads, sure, but what happens to those
shouldn't affect job execution, and failing as early as possible might actually
be a benefit.
I actually meant it the other way around. What happens if we have job1 and
job2, where the CL of job1 is leaked forward while executing job2. The TM would
die taking job2 with it with a somewhat unrelated error. In particular, I'd
think it would be pretty confusing/inperformant for larger batch clusters.
@StephanEwen WDYT?
But since I'm also a fan of failing early, I'd go that way once Stephan
agrees (I kinda had the impression that he wanted it to be graceful).
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