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_r394150929
########## 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: > No, with fail early I meant that the (leaked) thread with the leaked classloader reference would crash ASAP if it tries to load a class when the CL was closed. That sounds completely fine with me, but are we sure the CL is only leaked by leaking the thread? I understood that the Apache Commons Logging framework lives outside of the thread (in app classloader) and keeps the reference to the user classloader for the whole TM lifecycle. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services