Examples of org.apache.zookeeper.ZooKeeper

org.apache.zookeeper.ZooKeeper
This is the main class of ZooKeeper client library. To use a ZooKeeper service, an application must first instantiate an object of ZooKeeper class. All the iterations will be done by calling the methods of ZooKeeper class.
Once a connection to a server is established, a session ID is assigned to the client. The client will send heart beats to the server periodically to keep the session valid.
The application can call ZooKeeper APIs through a client as long as the session ID of the client remains valid.
If for some reason, the client fails to send heart beats to the server for a prolonged period of time (exceeding the sessionTimeout value, for instance), the server will expire the session, and the session ID will become invalid. The client object will no longer be usable. To make ZooKeeper API calls, the application must create a new client object.
If the ZooKeeper server the client currently connects to fails or otherwise does not respond, the client will automatically try to connect to another server before its session ID expires. If successful, the application can continue to use the client.
Some successful ZooKeeper API calls can leave watches on the "data nodes" in the ZooKeeper server. Other successful ZooKeeper API calls can trigger those watches. Once a watch is triggered, an event will be delivered to the client which left the watch at the first place. Each watch can be triggered only once. Thus, up to one event will be delivered to a client for every watch it leaves.
A client needs an object of a class implementing Watcher interface for processing the events delivered to the client. When a client drops current connection and re-connects to a server, all the existing watches are considered as being triggered but the undelivered events are lost. To emulate this, the client will generate a special event to tell the event handler a connection has been dropped. This special event has type EventNone and state sKeeperStateDisconnected.

  private static final int ID_LENGTH_SIZE =  Bytes.SIZEOF_INT;


  public RecoverableZooKeeper(String quorumServers, int seesionTimeout,
      Watcher watcher, int maxRetries, int retryIntervalMillis) 
  throws IOException {
    this.zk = new ZooKeeper(quorumServers, seesionTimeout, watcher);
    this.retryCounterFactory =
      new RetryCounterFactory(maxRetries, retryIntervalMillis);
    this.retryIntervalMillis = retryIntervalMillis;


    // the identifier = processID@hostName

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   */
  public static void waitForBaseZNode(Configuration conf) throws IOException {
    LOG.info("Waiting until the base znode is available");
    String parentZNode = conf.get(HConstants.ZOOKEEPER_ZNODE_PARENT,
        HConstants.DEFAULT_ZOOKEEPER_ZNODE_PARENT);
    ZooKeeper zk = new ZooKeeper(ZKConfig.getZKQuorumServersString(conf),
        conf.getInt(HConstants.ZK_SESSION_TIMEOUT,
        HConstants.DEFAULT_ZK_SESSION_TIMEOUT), EmptyWatcher.instance);


    final int maxTimeMs = 10000;
    final int maxNumAttempts = maxTimeMs / HConstants.SOCKET_RETRY_WAIT_MS;


    KeeperException keeperEx = null;
    try {
      try {
        for (int attempt = 0; attempt < maxNumAttempts; ++attempt) {
          try {
            if (zk.exists(parentZNode, false) != null) {
              LOG.info("Parent znode exists: " + parentZNode);
              keeperEx = null;
              break;
            }
          } catch (KeeperException e) {
            keeperEx = e;
          }
          Threads.sleepWithoutInterrupt(HConstants.SOCKET_RETRY_WAIT_MS);
        }
      } finally {
        zk.close();
      }
    } catch (InterruptedException ex) {
      Thread.currentThread().interrupt();
    }

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    }
    return ensureExists(znode.substring(0, index));
  }


  private boolean ensureExists(final String znode) {
    ZooKeeper zk = wrapper.getZooKeeper();
    try {
      Stat stat = zk.exists(znode, false);
      if (stat != null) {
        return true;
      }
      zk.create(znode, new byte[0], Ids.OPEN_ACL_UNSAFE, 
        CreateMode.PERSISTENT);
      return true;
    } catch (KeeperException.NodeExistsException e) {
      return true;      // ok, move on.
    } catch (KeeperException.NoNodeException e) {

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    }
  }


  @Override
  public User getUserForToken(String token) throws IOException {
    ZooKeeper zk = wrapper.getZooKeeper();
    try {
      byte[] data = zk.getData(usersZNode + "/" + token, null, null);
      if (data == null) {
        return null;
      }
      UserModel model = 
        unmarshaller.unmarshalFromJSON(new ByteArrayInputStream(data),

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  }


  private boolean ensureExists(final String znode, final CreateMode mode,
      final byte[] data) {
    try {
      ZooKeeper zk = wrapper.getZooKeeper();
      Stat stat = zk.exists(znode, false);
      if (stat != null) {
        zk.setData(znode, data, -1);
        return true;
      }
      zk.create(znode, data, Ids.OPEN_ACL_UNSAFE, mode);
      LOG.info("Created ZNode " + znode);
      return true;
    } catch (KeeperException.NodeExistsException e) {
      return true;      // ok, move on.
    } catch (KeeperException.NoNodeException e) {

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  @Override
  public void setUp() throws Exception {
    super.setUp();
    authenticator = new ZooKeeperAuthenticator(conf);
    ZooKeeper zk = authenticator.wrapper.getZooKeeper();
    JSONJAXBContext context =
      new JSONJAXBContext(JSONConfiguration.natural().build(),
          UserModel.class);
    JSONMarshaller marshaller = context.createJSONMarshaller();
    if (zk.exists(ZooKeeperAuthenticator.USERS_ZNODE_ROOT + "/" + 
          ADMIN_TOKEN, null) == null) {
      UserModel model = new UserModel();
      model.name = ADMIN_USERNAME;
      model.admin = true;
      ByteArrayOutputStream os = new ByteArrayOutputStream();
      marshaller.marshallToJSON(model, os);
      zk.create(ZooKeeperAuthenticator.USERS_ZNODE_ROOT + "/" + ADMIN_TOKEN, 
        os.toByteArray(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
    }
    if (zk.exists(ZooKeeperAuthenticator.USERS_ZNODE_ROOT + "/" + 
          USER_TOKEN, null) == null) {
      UserModel model = new UserModel();
      model.name = USER_USERNAME;
      ByteArrayOutputStream os = new ByteArrayOutputStream();
      marshaller.marshallToJSON(model, os);
      zk.create(ZooKeeperAuthenticator.USERS_ZNODE_ROOT + "/" + USER_TOKEN, 
        os.toByteArray(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
    }
    if (zk.exists(ZooKeeperAuthenticator.USERS_ZNODE_ROOT + "/" + 
          DISABLED_TOKEN, null) == null) {
      UserModel model = new UserModel();
      model.name = DISABLED_USERNAME;
      model.disabled = true;
      ByteArrayOutputStream os = new ByteArrayOutputStream();
      marshaller.marshallToJSON(model, os);
      zk.create(ZooKeeperAuthenticator.USERS_ZNODE_ROOT + "/" +DISABLED_TOKEN,
        os.toByteArray(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
    }
  }

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        IMocksControl c = EasyMock.createNiceControl();


        BundleContext ctx = c.createMock(BundleContext.class);
        ZooKeeperDiscovery zkd = c.createMock(ZooKeeperDiscovery.class);


        ZooKeeper zk = c.createMock(ZooKeeper.class);
        EasyMock.expect(zk.getState()).andReturn(ZooKeeper.States.CONNECTED).anyTimes();


        EasyMock.expect(zkd.getZookeeper()).andReturn(zk).anyTimes();


        EndpointListenerTrackerCustomizer.Interest interest = new EndpointListenerTrackerCustomizer.Interest();


        String scope = "(myProp=test)";
        String interf = "es.schaaf.test";
        String node = Util.getZooKeeperPath(interf);


        final InterfaceDataMonitorListenerImpl idmli = c.createMock(InterfaceDataMonitorListenerImpl.class);


        InterfaceMonitor im = new InterfaceMonitor(zk, interf, interest, scope, ctx) {
            @Override
            protected InterfaceDataMonitorListenerImpl createInterfaceDataMonitorListener(ZooKeeper zk,
                                                                                          String intf,
                                                                                          Interest zkd,
                                                                                          String scope,
                                                                                          BundleContext bctx) {
                return idmli;
            }
        };


        idmli.change();
        EasyMock.expectLastCall().once();


        zk.exists(EasyMock.eq(node), EasyMock.eq(im), EasyMock.eq(im), EasyMock.anyObject());
        EasyMock.expectLastCall().once();


        EasyMock.expect(zk.exists(EasyMock.eq(node), EasyMock.eq(false))).andReturn(new Stat()).anyTimes();


        EasyMock.expect(zk.getChildren(EasyMock.eq(node), EasyMock.eq(im))).andReturn(Collections.EMPTY_LIST)
            .once();


        c.replay();


        im.start();

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        IMocksControl c = EasyMock.createNiceControl();


        BundleContext ctx = c.createMock(BundleContext.class);
        ZooKeeperDiscovery zkd = c.createMock(ZooKeeperDiscovery.class);


        ZooKeeper zk = c.createMock(ZooKeeper.class);


        EasyMock.expect(zkd.getZookeeper()).andReturn(zk).anyTimes();


        
        String path = "/osgi/service_registry/myClass/google.de#80##test";
        EasyMock.expect(
                        zk.create(EasyMock.eq(path),
                                  (byte[])EasyMock.anyObject(), EasyMock.eq(Ids.OPEN_ACL_UNSAFE), EasyMock
                                      .eq(CreateMode.EPHEMERAL))).andReturn("").once();
        
        zk.delete(EasyMock.eq("/osgi/service_registry/myClass/google.de#80##test"), EasyMock.eq(-1));
        EasyMock.expectLastCall().once();


        c.replay();


        EndpointListenerImpl eli = new EndpointListenerImpl(zkd, ctx);

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   */
  public static void waitForBaseZNode(Configuration conf) throws IOException {
    LOG.info("Waiting until the base znode is available");
    String parentZNode = conf.get(HConstants.ZOOKEEPER_ZNODE_PARENT,
        HConstants.DEFAULT_ZOOKEEPER_ZNODE_PARENT);
    ZooKeeper zk = new ZooKeeper(ZKConfig.getZKQuorumServersString(conf),
        conf.getInt(HConstants.ZK_SESSION_TIMEOUT,
        HConstants.DEFAULT_ZK_SESSION_TIMEOUT), EmptyWatcher.instance);


    final int maxTimeMs = 10000;
    final int maxNumAttempts = maxTimeMs / HConstants.SOCKET_RETRY_WAIT_MS;


    KeeperException keeperEx = null;
    try {
      try {
        for (int attempt = 0; attempt < maxNumAttempts; ++attempt) {
          try {
            if (zk.exists(parentZNode, false) != null) {
              LOG.info("Parent znode exists: " + parentZNode);
              keeperEx = null;
              break;
            }
          } catch (KeeperException e) {
            keeperEx = e;
          }
          Threads.sleepWithoutInterrupt(HConstants.SOCKET_RETRY_WAIT_MS);
        }
      } finally {
        zk.close();
      }
    } catch (InterruptedException ex) {
      Thread.currentThread().interrupt();
    }

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        System.out.println("In Old connection New session");
      }
    };
    _zkClient.subscribeStateChanges(listener);
    ZkConnection connection = ((ZkConnection) _zkClient.getConnection());
    ZooKeeper zookeeper = connection.getZookeeper();
    System.out.println("old sessionId= " + zookeeper.getSessionId());
    try
    {
      Watcher watcher = new Watcher(){
        @Override
        public void process(WatchedEvent event)
        {
          System.out.println("In New connection In process event:"+ event);
        }
      };
      ZooKeeper newZookeeper = new ZooKeeper(connection.getServers(),
          zookeeper.getSessionTimeout(), watcher , zookeeper.getSessionId(),
          zookeeper.getSessionPasswd());
      Thread.sleep(3000);
      System.out.println("New sessionId= " + newZookeeper.getSessionId());
      Thread.sleep(3000);
      newZookeeper.close();
      Thread.sleep(10000);
      connection = ((ZkConnection) _zkClient.getConnection());
      zookeeper = connection.getZookeeper();
      System.out.println("After session expiry sessionId= " + zookeeper.getSessionId());
    } catch (Exception e)

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