testLateListenerIsOrderedCorrectly() — netty Function Reference

Source Code

common/src/test/java/io/netty/util/concurrent/DefaultPromiseTest.java lines 486–540

    private static void testLateListenerIsOrderedCorrectly(Throwable cause) throws InterruptedException {
        final EventExecutor executor = new TestEventExecutor();
        try {
            final AtomicInteger state = new AtomicInteger();
            final CountDownLatch latch1 = new CountDownLatch(1);
            final CountDownLatch latch2 = new CountDownLatch(2);
            final Promise<Void> promise = new DefaultPromise<Void>(executor);

            // Add a listener before completion so "lateListener" is used next time we add a listener.
            promise.addListener((FutureListener<Void>) future -> assertTrue(state.compareAndSet(0, 1)));

            // Simulate write operation completing, which will execute listeners in another thread.
            if (cause == null) {
                promise.setSuccess(null);
            } else {
                promise.setFailure(cause);
            }

            // Add a "late listener"
            promise.addListener((FutureListener<Void>) future -> {
                assertTrue(state.compareAndSet(1, 2));
                latch1.countDown();
            });

            // Wait for the listeners and late listeners to be completed.
            latch1.await();
            assertEquals(2, state.get());

            // This is the important listener. A late listener that is added after all late listeners
            // have completed, and needs to update state before a read operation (on the same executor).
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    promise.addListener((FutureListener<Void>) future -> {
                        assertTrue(state.compareAndSet(2, 3));
                        latch2.countDown();
                    });
                }
            });

            // Simulate a read operation being queued up in the executor.
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    // This is the key, we depend upon the state being set in the next listener.
                    assertEquals(3, state.get());
                    latch2.countDown();
                }
            });

            latch2.await();
        } finally {
            executor.shutdownGracefully(0, 0, TimeUnit.SECONDS).sync();
        }
    }