| /* |
| * 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.cassandra.simulator.test; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import org.junit.Assert; |
| import org.junit.Test; |
| |
| import org.apache.cassandra.concurrent.ExecutorFactory; |
| import org.apache.cassandra.concurrent.ExecutorPlus; |
| import org.apache.cassandra.distributed.api.IIsolatedExecutor; |
| |
| // A simple demonstration of manipulating the order of JVM level events using the simulation framework |
| public class MonitorMethodTransformerTest extends SimulationTestBase |
| { |
| @Test |
| public void testSynchronizedMethod() |
| { |
| // This verifies that the simulation does introduce some change to the order in which |
| // system events are scheduled. Ordinarily, we would expect each runnable to execute |
| // in a purely serial manner. However, injecting them into the simulated system adds |
| // a degree of (pseudorandom) non-determinism around the ordering of: |
| // * the scheduling of the threads executing the tasks, when they park / unpark |
| // * the fairness of acquiring the monitor needed to enter the synchronized method |
| // so we expect to see an interleaving of the thread ids executing the synchronized |
| // method. |
| // The simulated system doesn't alter the semantics of the JVM however, so |
| // synchronization still ensures single threaded access to critical sections. The |
| // synchronized method itself includes a check to verify this. |
| ClassWithSynchronizedMethods.executions.clear(); |
| IIsolatedExecutor.SerializableRunnable[] runnables = new IIsolatedExecutor.SerializableRunnable[10]; |
| for (int j = 0; j < 10; j++) |
| { |
| int thread = j; |
| runnables[j] = () -> { |
| for (int iteration = 0; iteration < 10; iteration++) |
| { |
| ClassWithSynchronizedMethods.synchronizedMethodWithParams(thread, iteration); |
| } |
| }; |
| } |
| |
| simulate(runnables, |
| () -> checkInterleavings()); |
| } |
| |
| @Test |
| public void testSynchronizedMethodMultiThreaded() |
| { |
| // Similar to the method above, but this test adds submission of tasks to an Executor |
| // within the simulated system, effectively adding another layer of scheduling to be |
| // perturbed. The same invariants should preserved as in the previous test. |
| simulate(() -> { |
| ExecutorPlus executor = ExecutorFactory.Global.executorFactory().pooled("name", 10); |
| int threads = 10; |
| for (int i = 0; i < threads; i++) |
| { |
| int thread = i; |
| executor.submit(() -> { |
| for (int iteration = 0; iteration < 10; iteration++) |
| ClassWithSynchronizedMethods.synchronizedMethodWithParams(thread, iteration); |
| }); |
| } |
| }, |
| () -> checkInterleavings()); |
| } |
| |
| public static void checkInterleavings() |
| { |
| List<Integer> seenThreads = new ArrayList<>(); |
| // check if synchronized methods called by different threads did interleave |
| for (ClassWithSynchronizedMethods.Execution execution : ClassWithSynchronizedMethods.executions) |
| { |
| int idx = seenThreads.indexOf(execution.thread); |
| if (seenThreads.size() > 1) |
| { |
| // This thread was present in the list, and it is not the last one |
| if (idx > 0 && idx != seenThreads.size() - 1) |
| { |
| System.out.println(String.format("Detected interleaving between %d and %d", |
| execution.thread, seenThreads.get(seenThreads.size() - 1))); |
| return; |
| } |
| } |
| |
| if (idx == -1) |
| seenThreads.add(execution.thread); |
| } |
| Assert.fail("No interleavings detected"); |
| } |
| } |
| |