[JEXL-206] testCallableCancel() test hangs sporadically

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0
• Fix Version/s: 3.1
• Assignee: Henri Biestro
• Reporter: Dmitri Blinov
• Created: 12/Jul/16 09:02
• Updated: 29/Jun/21 06:59
• Resolved: 14/Jul/16 15:04

Description

I'm struggling with strange behaviour of the building process, it seems that time after time the process hangs somewhere in the middle of the tests stage. First I thought it was somehow related to memory problems so I changed fork mode of the test plugin by adding <forkMode>pertest</forkMode> to maven-surefire-plugin configuration. But that helped for a couple of times to cleanly build jexl and run all tests successfully. The other times it simply hanged on test stage. I have managed to detect that it is the testCallableCancel() test that hangs. One of its worker threads has a stack trace as follows:

org.apache.commons.jexl3.internal.Interpreter.visit(Interpreter.java:893)
org.apache.commons.jexl3.parser.ASTWhileStatement.jjtAccept(ASTWhileStatement.java:18)
org.apache.commons.jexl3.internal.Interpreter.visit(Interpreter.java:1119)
org.apache.commons.jexl3.parser.ASTJexlScript.jjtAccept(ASTJexlScript.java:55)
org.apache.commons.jexl3.internal.Interpreter.interpret(Interpreter.java:210)
org.apache.commons.jexl3.internal.Script$Callable.interpret(Script.java:364)
org.apache.commons.jexl3.internal.Script$Callable.call(Script.java:372)
   - locked org.apache.commons.jexl3.internal.Script$Callable@18399f62
java.util.concurrent.FutureTask.run(FutureTask.java:262)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
java.lang.Thread.run(Thread.java:745)

I have adjusted the test code with prinln() to dig further what is going on:

    @Test
    public void testCallableCancel() throws Exception {

        System.out.println("testCallableCancel(): started");

        JexlScript e = JEXL.createScript("while(true);");
        final Script.Callable c = (Script.Callable) e.callable(null);
        Object t = 42;
        Callable<Object> kc = new Callable<Object>() {
            @Override
            public Object call() throws Exception {
                System.out.println("testCallableCancel(): cancel() is called");
                return c.cancel();
            }

        };

        Callable<Object> xkc = new Callable<Object>() {
            @Override
            public Object call() throws Exception {
                System.out.println("testCallableCancel(): run() is called");
                return c.call();
            }

        };

        ExecutorService executor = Executors.newFixedThreadPool(2);
        Future<?> future = executor.submit(xkc);
        Future<?> kfc = executor.submit(kc);
        try {
            Assert.assertTrue((Boolean) kfc.get());

            System.out.println("testCallableCancel(): canceled()");

            t = future.get();
            Assert.fail("should have been cancelled");
        } catch (ExecutionException xexec) {
            // ok, ignore
            Assert.assertTrue(xexec.getCause() instanceof JexlException.Cancel);
        } finally {
            executor.shutdown();
        }
        Assert.assertTrue(c.isCancelled());

        System.out.println("testCallableCancel(): finished");
    }

If the test hangs it prints the following:

testCallableCancel(): started
testCallableCancel(): run() is called
testCallableCancel(): cancel() is called
testCallableCancel(): canceled()

If the test runs as normal and does not hang it prints the following:

testCallableCancel(): started
testCallableCancel(): run() is called
testCallableCancel(): cancel() is called
testCallableCancel(): canceled()
testCallableCancel(): finished