Redisson分佈式閉鎖RCountDownLatch的使用詳細講解

@Test
public void testRCountDownLatch() {
    Config config = new Config();
    config.useSingleServer().setAddress("redis://127.0.0.1:6379");
    RedissonClient redissonClient = Redisson.create(config);
    RCountDownLatch rCountDownLatch = redissonClient.getCountDownLatch("anyCountDownLatch");
    rCountDownLatch.trySetCount(5);
    for (int i = 1; i <= 5; i++) {
        new Thread(() -> {
            System.out.println(Thread.currentThread().getName() + "離開教師...");
            rCountDownLatch.countDown();
        }, "A" + i).start();
    }
    try {
        rCountDownLatch.await();
    } catch (InterruptedException e) {
        throw new RuntimeException(e);
    }
    System.out.println("班長鎖門...");
}

/**
 * 僅當先前的計數已達到零或根本未設置時才設置新的計數值。
 */
boolean trySetCount(long count);

public RFuture<Boolean> trySetCountAsync(long count) {
    return commandExecutor.evalWriteAsync(getRawName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
            // 往redis中寫入一個String類型的數據    anyCountDownLatch:5
            "if redis.call('exists', KEYS[1]) == 0 then "
                + "redis.call('set', KEYS[1], ARGV[2]); "
                + "redis.call('publish', KEYS[2], ARGV[1]); "
                + "return 1 "
            + "else "
                + "return 0 "
            + "end",
            Arrays.asList(getRawName(), getChannelName()), CountDownLatchPubSub.NEW_COUNT_MESSAGE, count);
}

public RFuture<Void> countDownAsync() {
    return commandExecutor.evalWriteNoRetryAsync(getRawName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
                    // 減少redis中計數器的值
                    "local v = redis.call('decr', KEYS[1]);" +
                    // 計數器減為0後，刪除對應的key        
                    "if v <= 0 then redis.call('del', KEYS[1]) end;" +
                    "if v == 0 then redis.call('publish', KEYS[2], ARGV[1]) end;",
                Arrays.<Object>asList(getRawName(), getChannelName()), CountDownLatchPubSub.ZERO_COUNT_MESSAGE);
}

public void await() throws InterruptedException {
    // 如果計數器為0，直接返回
    if (getCount() == 0) {
        return;
    }
    // 訂閱redisson_countdownlatch__channel__{anyCountDownLatch}的消息
    CompletableFuture<RedissonCountDownLatchEntry> future = subscribe();
    RedissonCountDownLatchEntry entry = commandExecutor.getInterrupted(future);
    try {
        // 不斷循環判斷計數器的值是否大於0，大於0說明還有線程沒執行完成，在這裡阻塞：LockSupport.park(this)
        while (getCount() > 0) {
            // waiting for open state
            entry.getLatch().await();
        }
    } finally {
        unsubscribe(entry);
    }
}