[ZOOKEEPER-3186] bug in barrier example code

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: documentation
• Assignee: Unassigned
• Reporter: cheng pan
• Created: 09/Nov/18 06:27
• Updated: 22/Nov/18 02:06

Description

the code given in the documentation

while (true) {
    synchronized (mutex) {
        List<String> list = zk.getChildren(root, true);
        if (list.size() < size) {
            mutex.wait();
        } else {
            return true;
        }
    }
}

When some nodes are not ready, the code calls mutex.wait() and waits for the watcher event to call mutex.notify() to wake it up. The problem is, we can't guarantee that mutex.notify() will definitely happen after mutex.wait(), which will cause client is stuck.
The solution might be CountDownLatch?