private void exists()

in twill-zookeeper/src/main/java/org/apache/twill/internal/zookeeper/RewatchOnExpireWatcher.java [94:126]

27 lines of code
7 McCabe index (conditional complexity)


  private void exists() {
    Futures.addCallback(client.exists(path, this), new FutureCallback<Stat>() {
      @Override
      public void onSuccess(Stat stat) {
        // Since we know all callbacks and watcher are triggered from single event thread, there is no race condition.
        Object oldResult = lastResult.getReference();
        lastResult.compareAndSet(oldResult, null, true, false);

        if (stat != oldResult && (stat == null || !stat.equals(oldResult))) {
          if (stat == null) {
            // previous stat is not null, means node deleted
            process(new WatchedEvent(Event.EventType.NodeDeleted, Event.KeeperState.SyncConnected, path));
          } else if (oldResult == null) {
            // previous stat is null, means node created
            process(new WatchedEvent(Event.EventType.NodeCreated, Event.KeeperState.SyncConnected, path));
          } else {
            // Otherwise, something changed on the node
            process(new WatchedEvent(Event.EventType.NodeDataChanged, Event.KeeperState.SyncConnected, path));
          }
        }
      }

      @Override
      public void onFailure(Throwable t) {
        if (RetryUtils.canRetry(t)) {
          exists();
        } else {
          lastResult.set(null, false);
          LOG.error("Fail to re-set watch on exists for path " + path, t);
        }
      }
    });
  }