Re: How to watch on descendant znodes using Curator PathCache?

[Jordan Zimmerman]

Do you need just the one level? If so, why not use PathChildrenCache: 
http://curator.apache.org/curator-recipes/path-cache.html

-JZ

From: Check Peck Check Peck
Reply: user@curator.apache.org user@curator.apache.org
Date: February 9, 2014 at 9:08:20 PM
To: user user@curator.apache.org
Subject:  How to watch on descendant znodes using Curator PathCache?  
I am working on a project in which I need to maintain a watches on a node, 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 - `"/my/test"` and I am keeping a watch on that node using 
the below code. What I want to do is, to keep the watch on `"/my/test"` znode. 
So suppose if these nodes gets added to my root node -

    "/my/test/test1"
    "/my/test/test2"
    "/my/test/test3"
   
Then I should get notified (till this part I am able to make it work) but if 
any new node gets added, updated or removed to `"/my/test/test1"`, 
`"/my/test/test2"` and `"/my/test/test3"` then I should also get notified and 
this is the part I am not able to understand how to make it work.

Whenever I am adding any new node to `"/my/test"` such as `"/my/test/test1"`, 
`"/my/test/test2"`, `"/my/test/test3"` then the watch gets triggered with the 
use of below code. But if I am adding any new node to `"/my/test/test1"` or 
`"/my/test/test2"`, 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?

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 `"/my/test"` children but not the 
childrens of `"/my/test/test1"` and etc etc.
  
    private static final String PATH = "/my/test";

    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) {
                }
            }
        } 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);
    }
   
Can anyone provide a simple example for this for my use case? I am using 
Curator 2.4.0 which got released recently.