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From Check Peck <comptechge...@gmail.com>
Subject How to watch on descendant znodes using Curator PathCache?
Date Mon, 10 Feb 2014 02:07:32 GMT
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.

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