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Recipe: Persistent Recursive Watcher

note

PersistentWatcher requires ZooKeeper 3.6+

Description​

A managed persistent watcher. The watch will be managed such that it stays set through connection lapses, etc.

Participating Classes​

  • PersistentWatcher

Creating a PersistentWatcher​

// Parameters:
// client - the client
// basePath - path to set the watch on
// recursive - ZooKeeper persistent watches can optionally be recursive
public PersistentWatcher(CuratorFramework client, String basePath, boolean recursive);

General Usage​

The instance must be started by calling start(). Call close() when you want to remove the watch.

PersistentWatcher presents two listener types:

  • Listenable<Watcher> getListenable() - Use this to add watchers. These will behave in the same manner that watchers added via ZooKeeper.addWatch() behave.
  • Listenable<Runnable> getResetListenable() - The Runnables added with this get called once the Persistent Watcher has been successfully set(or reset after a connection partition).

Error Handling​

PersistentWatcher instances internally monitor connection losses, etc. automatically resetting on reconnection.