[GitHub] [flink] XComp commented on a diff in pull request #22764: [FLINK-32314][rpc] Ignore classloading errors after actorsystem shutdown

["XComp (via GitHub)" <gi...@apache.org>]

XComp commented on code in PR #22764:
URL: https://github.com/apache/flink/pull/22764#discussion_r1228191494


##########
flink-rpc/flink-rpc-akka/src/main/java/org/apache/flink/runtime/rpc/akka/RobustActorSystem.java:
##########
@@ -85,17 +86,52 @@ private static RobustActorSystem create(
                                 .map(BootstrapSetup::defaultExecutionContext)
                                 .flatMap(RobustActorSystem::toJavaOptional));
 
+        final PostShutdownClassLoadingErrorFilter postShutdownClassLoadingErrorFilter =
+                new PostShutdownClassLoadingErrorFilter(uncaughtExceptionHandler);
+
         final RobustActorSystem robustActorSystem =
                 new RobustActorSystem(name, appConfig, classLoader, defaultEC, setup) {
                     @Override
                     public Thread.UncaughtExceptionHandler uncaughtExceptionHandler() {
-                        return uncaughtExceptionHandler.getOrElse(super::uncaughtExceptionHandler);
+                        return postShutdownClassLoadingErrorFilter;
                     }
                 };
+        robustActorSystem.registerOnTermination(
+                postShutdownClassLoadingErrorFilter::notifyShutdownComplete);
+
         robustActorSystem.start();
         return robustActorSystem;
     }
 
+    private static class PostShutdownClassLoadingErrorFilter
+            implements Thread.UncaughtExceptionHandler {
+
+        private final AtomicBoolean shutdownComplete = new AtomicBoolean();
+        private final Thread.UncaughtExceptionHandler uncaughtExceptionHandler;
+
+        public PostShutdownClassLoadingErrorFilter(
+                Thread.UncaughtExceptionHandler uncaughtExceptionHandler) {
+            this.uncaughtExceptionHandler = uncaughtExceptionHandler;
+        }
+
+        public void notifyShutdownComplete() {
+            shutdownComplete.set(true);
+        }
+
+        @Override
+        public void uncaughtException(Thread t, Throwable e) {
+            if (shutdownComplete.get()
+                    && (e instanceof NoClassDefFoundError || e instanceof ClassNotFoundException)) {

Review Comment:
   I'm wondering whether we should make this more restrictive (checking that the thread's name includes the `akka` keyword). So far, we have seen only `flink-akka` and `flink-metrics-akka` as the current thread in issues reported under FLINK-32189.



##########
flink-rpc/flink-rpc-akka/src/main/java/org/apache/flink/runtime/rpc/akka/RobustActorSystem.java:
##########


Review Comment:
   It's not part of the change but why do we have to declare `RobustActorSystem` as abstract and overwriting the `uncaughtExceptionHandler()` instead of setting the exception handler through the constructor and implementing the method properly? :thinking: 



##########
flink-rpc/flink-rpc-akka/src/test/java/org/apache/flink/runtime/rpc/akka/RobustActorSystemTest.java:
##########
@@ -84,6 +84,34 @@ void testUncaughtExceptionHandlerFromActor() {
         assertThat(uncaughtException).isSameAs(error);
     }
 
+    @Test
+    void testHonorClassloadingErrorBeforeShutdown() {
+        robustActorSystem
+                .uncaughtExceptionHandler()
+                .uncaughtException(Thread.currentThread(), new NoClassDefFoundError(""));
+
+        assertThat(testingUncaughtExceptionHandler.findUncaughtExceptionNow()).isPresent();
+    }
+
+    @Test
+    void testIgnoreClassloadingErrorAfterShutdown() {

Review Comment:
   nit: this test could be split up in two test methods (or through a parameterized test), e.g.:
   
   ```
       @ParameterizedTest
       @ValueSource(classes = {NoClassDefFoundError.class, ClassNotFoundException.class})
       void testIgnoreClassloadingErrorAfterShutdown(Class<? extends Throwable> clazz)
               throws InstantiationException, IllegalAccessException {
           // wait for termination
           robustActorSystem.terminate();
           robustActorSystem.getWhenTerminated().toCompletableFuture().join();
   
           robustActorSystem
                   .uncaughtExceptionHandler()
                   .uncaughtException(Thread.currentThread(), clazz.newInstance());
   
           assertThat(testingUncaughtExceptionHandler.findUncaughtExceptionNow()).isEmpty();
       }
   ```



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