gharris1727 commented on a change in pull request #8259: URL: https://github.com/apache/kafka/pull/8259#discussion_r585020737
########## File path: connect/runtime/src/test/java/org/apache/kafka/connect/runtime/isolation/SynchronizationTest.java ########## @@ -0,0 +1,468 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.kafka.connect.runtime.isolation; + +import static org.junit.Assert.fail; + +import java.lang.management.LockInfo; +import java.lang.management.ManagementFactory; +import java.lang.management.MonitorInfo; +import java.lang.management.ThreadInfo; +import java.net.URL; +import java.security.AccessController; +import java.security.PrivilegedAction; +import java.util.Arrays; +import java.util.Collections; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.concurrent.BrokenBarrierException; +import java.util.concurrent.CyclicBarrier; +import java.util.concurrent.LinkedBlockingDeque; +import java.util.concurrent.ThreadFactory; +import java.util.concurrent.ThreadPoolExecutor; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.TimeoutException; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.function.Predicate; +import java.util.stream.Collectors; +import org.apache.kafka.common.config.AbstractConfig; +import org.apache.kafka.common.config.ConfigDef; +import org.apache.kafka.common.config.ConfigDef.Importance; +import org.apache.kafka.common.config.ConfigDef.Type; +import org.apache.kafka.connect.runtime.WorkerConfig; +import org.junit.After; +import org.junit.Before; +import org.junit.Rule; +import org.junit.Test; +import org.junit.rules.TestName; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +public class SynchronizationTest { + + public static final Logger log = LoggerFactory.getLogger(SynchronizationTest.class); + + @Rule + public final TestName testName = new TestName(); + + private String threadPrefix; + private Plugins plugins; + private ThreadPoolExecutor exec; + private Breakpoint<String> dclBreakpoint; + private Breakpoint<String> pclBreakpoint; + + @Before + public void setup() { + TestPlugins.assertAvailable(); + Map<String, String> pluginProps = Collections.singletonMap( + WorkerConfig.PLUGIN_PATH_CONFIG, + String.join(",", TestPlugins.pluginPath()) + ); + threadPrefix = SynchronizationTest.class.getSimpleName() + + "." + testName.getMethodName() + "-"; + dclBreakpoint = new Breakpoint<>(); + pclBreakpoint = new Breakpoint<>(); + plugins = new Plugins(pluginProps) { + @Override + protected DelegatingClassLoader newDelegatingClassLoader(List<String> paths) { + return AccessController.doPrivileged( + (PrivilegedAction<DelegatingClassLoader>) () -> + new SynchronizedDelegatingClassLoader(paths) + ); + } + }; + exec = new ThreadPoolExecutor( + 2, + 2, + 1000L, + TimeUnit.MILLISECONDS, + new LinkedBlockingDeque<>(), + threadFactoryWithNamedThreads(threadPrefix) + ); + + } + + @After + public void tearDown() throws InterruptedException { + dclBreakpoint.clear(); + pclBreakpoint.clear(); + exec.shutdown(); + exec.awaitTermination(1L, TimeUnit.SECONDS); + } + + private static class Breakpoint<T> { + + private Predicate<T> predicate; + private CyclicBarrier barrier; + + public synchronized void clear() { + if (barrier != null) { + barrier.reset(); + } + predicate = null; + barrier = null; + } + + public synchronized void set(Predicate<T> predicate) { + clear(); + this.predicate = predicate; + // As soon as the barrier is tripped, the barrier will be reset for the next round. + barrier = new CyclicBarrier(2); + } + + /** + * From a thread under test, await for the test orchestrator to continue execution + * @param obj Object to test with the breakpoint's current predicate + */ + public void await(T obj) { + Predicate<T> predicate; + CyclicBarrier barrier; + synchronized (this) { + predicate = this.predicate; + barrier = this.barrier; + } + if (predicate != null && !predicate.test(obj)) { + return; + } + if (barrier != null) { + try { + barrier.await(); + } catch (InterruptedException | BrokenBarrierException e) { + throw new RuntimeException("Interrupted while waiting for load gate", e); + } + } + } + + /** + * From the test orchestrating thread, await for the test thread to continue execution + * @throws InterruptedException If the current thread is interrupted while waiting + * @throws BrokenBarrierException If the test thread is interrupted while waiting + * @throws TimeoutException If the barrier is not reached before 1s passes. + */ + public void testAwait() + throws InterruptedException, BrokenBarrierException, TimeoutException { + CyclicBarrier barrier; + synchronized (this) { + barrier = this.barrier; + } + Objects.requireNonNull(barrier, "Barrier must be set up before awaiting"); + barrier.await(1L, TimeUnit.SECONDS); + } + } + + private class SynchronizedDelegatingClassLoader extends DelegatingClassLoader { + + public SynchronizedDelegatingClassLoader(List<String> pluginPaths) { + super(pluginPaths); + } + + @Override + protected PluginClassLoader newPluginClassLoader( + URL pluginLocation, + URL[] urls, + ClassLoader parent + ) { + return AccessController.doPrivileged( + (PrivilegedAction<PluginClassLoader>) () -> + new SynchronizedPluginClassLoader(pluginLocation, urls, parent) + ); + } + + @Override + public PluginClassLoader pluginClassLoader(String name) { + dclBreakpoint.await(name); + dclBreakpoint.await(name); + return super.pluginClassLoader(name); + } + } + + private class SynchronizedPluginClassLoader extends PluginClassLoader { + { + ClassLoader.registerAsParallelCapable(); + } + + + public SynchronizedPluginClassLoader(URL pluginLocation, URL[] urls, ClassLoader parent) { + super(pluginLocation, urls, parent); + } + + @Override + protected Object getClassLoadingLock(String className) { + pclBreakpoint.await(className); + return super.getClassLoadingLock(className); + } + } + + @Test(timeout = 15000L) + // If the test times out, then there's a deadlock in the test but not necessarily the code + public void workerContextClassLoaderMismatch() throws Exception { + // Grab a reference to the target PluginClassLoader before activating breakpoints + ClassLoader connectorLoader = plugins.delegatingLoader() + .connectorLoader(TestPlugins.SAMPLING_CONVERTER); + + // Simulate Worker::startConnector that creates configs with the delegating classloader + Runnable delegatingToPlugin = () -> { + // Use the DelegatingClassLoader as the current context loader + ClassLoader savedLoader = Plugins.compareAndSwapLoaders(plugins.delegatingLoader()); + + // Load an isolated plugin from the delegating classloader, which will + // 1. Lock the DelegatingClassLoader (via Class.forName) + // 2. Wait for test to continue + // 3. Attempt to lock the PluginClassLoader (via PluginClassLoader::loadClass) + // 4. Deadlock + new AbstractConfig( + new ConfigDef().define("a.class", Type.CLASS, Importance.HIGH, ""), + Collections.singletonMap("a.class", TestPlugins.SAMPLING_CONVERTER)); + Plugins.compareAndSwapLoaders(savedLoader); + }; + // DelegatingClassLoader breakpoint will only trigger on this thread + dclBreakpoint.set(TestPlugins.SAMPLING_CONVERTER::equals); + + // Simulate Worker::startTask that creates configs with the plugin classloader + Runnable pluginToDelegating = () -> { + // Use the PluginClassLoader as the current context loader + ClassLoader savedLoader = Plugins.compareAndSwapLoaders(connectorLoader); + // Load a non-isolated class from the plugin classloader, which will + // 1. Lock the PluginClassLoader (via PluginClassLoader::loadClass) + // 2. Wait for the test to continue + // 3. Attempt to lock the DelegatingClassLoader (via ClassLoader::loadClass) + // 4. Deadlock + new AbstractConfig(new ConfigDef().define("a.class", Type.CLASS, Importance.HIGH, ""), + Collections.singletonMap("a.class", "org.apache.kafka.connect.storage.JsonConverter")); + Plugins.compareAndSwapLoaders(savedLoader); + }; + // PluginClassLoader breakpoint will only trigger on this thread + pclBreakpoint.set("org.apache.kafka.connect.storage.JsonConverter"::equals); + + // Step 1: Lock the delegating classloader and pause + exec.submit(delegatingToPlugin); + // d2p enters ConfigDef::parseType + // d2p enters DelegatingClassLoader::loadClass + dclBreakpoint.testAwait(); + dclBreakpoint.testAwait(); + // d2p exits DelegatingClassLoader::loadClass + // d2p enters Class::forName + // d2p LOCKS DelegatingClassLoader + // d2p enters DelegatingClassLoader::loadClass + dclBreakpoint.testAwait(); + // d2p waits in the delegating classloader while we set up the other thread + dumpThreads("d2p waiting with DelegatingClassLoader locked"); + + // Step 2: Lock the plugin classloader and then the delegating classloader + exec.submit(pluginToDelegating); + // p2d enters PluginClassLoader::loadClass + // p2d LOCKS PluginClassLoader + pclBreakpoint.testAwait(); + // p2d locks the class-specific classLoadingLock + // p2d falls through to ClassLoader::loadClass + pclBreakpoint.testAwait(); + // p2d locks the class-specific classLoadingLock + // p2d delegates upwards to DelegatingClassLoader::loadClass + // p2d enters ClassLoader::loadClass + // p2d LOCKS DelegatingClassLoader (starting the deadlock) + dumpThreads("p2d blocked trying to acquire the DelegatingClassLoader lock"); + + // Step 3: Resume the first thread and try to lock the plugin classloader + dclBreakpoint.testAwait(); + // d2p enters PluginClassLoader::loadClass + // d2p LOCKS PluginClassLoader (completing the deadlock) + dumpThreads("d2p blocked trying to acquire the PluginClassLoader lock"); + assertNoDeadlocks(); + } + + // This is an informative test that is supposed to fail, demonstrating that forName is + // locking the connectorLoader in this JVM implementation, when initialize is true. + @Test Review comment: This test was useful for narrowing down on the root-cause of the issue (forName locking the PCL) and it's nice to see that the deadlock in both tests was prevented by the fix. I think it was oversight on my part to mark it expected, as at the time I believed that it was the expected behavior. I realize now that it was a side-effect of the bug, and of the classloader not being marked parallel. At this time, I would call this test a targeted subset ("unit") of the above test ("integration"), and is pretty low-cost to keep around. ---------------------------------------------------------------- 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
