Examples of com.hazelcast.core.ISemaphore

com.hazelcast.core.ISemaphore
ISemaphore is a backed-up distributed alternative to the {@link java.util.concurrent.Semaphore}.
ISemaphore is a cluster-wide counting semaphore. Conceptually, it maintains a set of permits. Each {@link #acquire()} blocks if necessary untila permit is available, and then takes it. Each {@link #release()} adds a permit,potentially releasing a blocking acquirer. However, no actual permit objects are used; the semaphore just keeps a count of the number available and acts accordingly.
The Hazelcast distributed semaphore implementation guarantees that threads invoking any of the {@link #acquire() acquire} methods are selectedto obtain permits in the order in which their invocation of those methods was processed(first-in-first-out; FIFO). Note that FIFO ordering necessarily applies to specific internal points of execution within the cluster. So, it is possible for one member to invoke {@code acquire} before another, but reachthe ordering point after the other, and similarly upon return from the method.
This class also provides convenience methods to {@link #acquire(int) acquire} and {@link #release(int) release} multiplepermits at a time. Beware of the increased risk of indefinite postponement when using the multiple acquire. If a single permit is released to a semaphore that is currently blocking, a thread waiting for one permit will acquire it before a thread waiting for multiple permits regardless of the call order.
- Correct usage of a semaphore is established by programming convention in the application.

        assertTrue(semaphore.tryAcquire(1, TimeUnit.MILLISECONDS));
    }


    @Test
    public void testTryAcquire_whenUnAvailableWithTimeOut() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(0);
        assertFalse(semaphore.tryAcquire(1, TimeUnit.MILLISECONDS));
    }

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        assertFalse(semaphore.tryAcquire(1, TimeUnit.MILLISECONDS));
    }


    @Test
    public void testTryAcquireMultiPermits_whenAvailable() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(10);
        assertTrue(semaphore.tryAcquire(5));
    }

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        assertTrue(semaphore.tryAcquire(5));
    }


    @Test
    public void testTryAcquireMultiPermits_whenUnAvailable() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(5);
        assertFalse(semaphore.tryAcquire(10));
    }

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        assertFalse(semaphore.tryAcquire(10));
    }


    @Test
    public void testTryAcquireMultiPermits_whenAvailableWithTimeOut() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(10);
        assertTrue(semaphore.tryAcquire(5, 1, TimeUnit.MILLISECONDS));
    }

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        assertTrue(semaphore.tryAcquire(5, 1, TimeUnit.MILLISECONDS));
    }


    @Test
    public void testTryAcquireMultiPermits_whenUnAvailableWithTimeOut() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(5);
        assertFalse(semaphore.tryAcquire(10, 1, TimeUnit.MILLISECONDS));
    }

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        assertFalse(semaphore.tryAcquire(10, 1, TimeUnit.MILLISECONDS));
    }


    @Test
    public void testTryAcquire_afterRelease() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(0);
        semaphore.release();
        assertTrue(semaphore.tryAcquire());
    }

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        assertTrue(semaphore.tryAcquire());
    }


    @Test
    public void testMulitReleaseTryAcquire() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(0);
        semaphore.release(5);
        assertTrue(semaphore.tryAcquire(5));
    }

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        assertTrue(semaphore.tryAcquire(5));
    }


    @Test
    public void testAcquire_Threaded() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(0);


        final CountDownLatch latch = new CountDownLatch(1);
        new Thread(){
            public void run() {
                try {
                    semaphore.acquire();
                    latch.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }.start();
        Thread.sleep(1000);
        semaphore.release(2);


        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertEquals(1, semaphore.availablePermits());
    }

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        assertEquals(1, semaphore.availablePermits());
    }


    @Test
    public void tryAcquire_Threaded() throws Exception {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(0);


        final CountDownLatch latch = new CountDownLatch(1);
        new Thread(){
            public void run() {
                try {
                    if(semaphore.tryAcquire(1, 5, TimeUnit.SECONDS)){
                        latch.countDown();
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }.start();


        semaphore.release(2);
        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertEquals(1, semaphore.availablePermits());
    }

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    public void concurrent_trySemaphoreWithTimeOutTest() {
        concurrent_trySemaphoreTest(true);
    }


    public void concurrent_trySemaphoreTest(final boolean tryWithTimeOut) {
        final ISemaphore semaphore = client.getSemaphore(randomString());
        semaphore.init(1);
        final AtomicInteger upTotal = new AtomicInteger(0);
        final AtomicInteger downTotal = new AtomicInteger(0);


        final SemaphoreTestThread threads[] = new SemaphoreTestThread[8];
        for(int i=0; i<threads.length; i++){

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