RE: How to watch for events on all descendant nodes in ZooKeeper using curator?

[Senecal, Shaun | Shaun | BDD]

You need to set a child watcher on each node you want to watch.   So if you 
initially set a watch on "/rj/colo", then a new node is created (ie: 
"/rj/colo/phx") you need to add a new watch on the new node as well.


________________________________
From: Techy Teck [comptechge...@gmail.com]
Sent: Monday, November 18, 2013 1:35 PM
To: user
Subject: How to watch for events on all descendant nodes in ZooKeeper using 
curator?

I am working on a project in which I need to maintain a watches on a node, and 
that nodes children and that nodes children as well. I have tried using 
PathCache but I am not sure how to watch for childrens children here?

Here my root node is - "/rj/colo" and keeping a watch on that node as well.

Whenever I am adding any new node to "/rj/colo" such as "/rj/colo/phx", 
"/rj/colo/slc", "/rj/colo/lvs" then the watch gets triggered. But if I am 
adding any new node to "/rj/colo/phx" or "/rj/colo/slc", then no watches get 
triggerd and I am not sure how to add the code for that as well? Any thoughts 
how this can be done efficiently? May be if somebody has done this in the 
past.. So any example will be of great help to me..

Below is my code which works fine for "/rj/colo" children but not the childrens 
of "/rj/colo/phx" and etc etc.

    private static final String PATH = "/rj/colo";

    public static void main(String[] args) {
        CuratorFramework client = null;
        PathChildrenCache cache = null;
        try {
            client = CuratorClient.createSimple("localhost:2181");
            client.start();

            // in this example we will cache data. Notice that this is optional.
            cache = new PathChildrenCache(client, PATH, true);
            cache.start();

            addListener(cache);

            for(;;) {
                try {
                    Thread.sleep(50000);
                } catch(InterruptedException e) {
                }
            }

            // processCommands(client, cache);
        } catch (Exception e1) {
            e1.printStackTrace();
        }
    }

Below is my addListener method -

    private static void addListener(PathChildrenCache cache) {

        PathChildrenCacheListener listener = new PathChildrenCacheListener() {
            public void childEvent(CuratorFramework client, 
PathChildrenCacheEvent event) throws Exception {
                switch (event.getType()) {
                case CHILD_ADDED: {
                    System.out.println("Node added: " + 
ZKPaths.getNodeFromPath(event.getData().getPath()));
                    break;
                }

                case CHILD_UPDATED: {
                    System.out.println("Node changed: "    + 
ZKPaths.getNodeFromPath(event.getData().getPath()));
                    break;
                }

                case CHILD_REMOVED: {
                    System.out.println("Node removed: "    + 
ZKPaths.getNodeFromPath(event.getData().getPath()));
                    break;
                }
                default:
                    break;
                }
            }
        };
        cache.getListenable().addListener(listener);
    }