Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ package org.apache.curator.framework.recipes.nodes; import com.google.common.base.Throwables; import com.google.common.collect.Lists; import org.apache.curator.framework.CuratorFramework; import org.apache.curator.framework.CuratorFrameworkFactory; import org.apache.curator.framework.api.ACLProvider; import org.apache.curator.framework.api.BackgroundCallback; import org.apache.curator.framework.api.CuratorEvent; import org.apache.curator.framework.state.ConnectionState; import org.apache.curator.framework.state.ConnectionStateListener; import org.apache.curator.retry.RetryOneTime; import org.apache.curator.test.BaseClassForTests; import org.apache.curator.test.KillSession; import org.apache.curator.test.Timing; import org.apache.curator.utils.CloseableUtils; import org.apache.curator.utils.ZKPaths; import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.Watcher.Event.EventType; import org.apache.zookeeper.ZooDefs; import org.apache.zookeeper.data.ACL; import org.apache.zookeeper.data.Stat; import org.testng.Assert; import org.testng.annotations.AfterMethod; import org.testng.annotations.Test; import java.io.IOException; import java.util.Arrays; import java.util.Collection; import java.util.Collections; import java.util.List; import java.util.concurrent.CountDownLatch; import java.util.concurrent.Semaphore; import java.util.concurrent.TimeUnit; import static org.testng.Assert.*; @SuppressWarnings("deprecation") public class TestPersistentEphemeralNode extends BaseClassForTests { private static final String DIR = "/test"; private static final String PATH = ZKPaths.makePath(DIR, "/foo"); private final Collection<CuratorFramework> curatorInstances = Lists.newArrayList(); private final Collection<PersistentEphemeralNode> createdNodes = Lists.newArrayList(); private final Timing timing = new Timing(); @AfterMethod public void teardown() throws Exception { for (PersistentEphemeralNode node : createdNodes) { node.close(); } for (CuratorFramework curator : curatorInstances) { curator.close(); } super.teardown(); } @Test public void testListenersReconnectedIsFast() throws Exception { server.stop(); CuratorFramework client = CuratorFrameworkFactory.newClient(server.getConnectString(), timing.session(), timing.connection(), new RetryOneTime(1)); try { client.start(); PersistentEphemeralNode node = new PersistentEphemeralNode(client, PersistentEphemeralNode.Mode.EPHEMERAL, "/abc/node", "hello".getBytes()); node.start(); final CountDownLatch connectedLatch = new CountDownLatch(1); final CountDownLatch reconnectedLatch = new CountDownLatch(1); ConnectionStateListener listener = new ConnectionStateListener() { @Override public void stateChanged(CuratorFramework client, ConnectionState newState) { if (newState == ConnectionState.CONNECTED) { connectedLatch.countDown(); } if (newState == ConnectionState.RECONNECTED) { reconnectedLatch.countDown(); } } }; client.getConnectionStateListenable().addListener(listener); timing.sleepABit(); server.restart(); Assert.assertTrue(timing.awaitLatch(connectedLatch)); timing.sleepABit(); Assert.assertTrue(node.waitForInitialCreate(timing.forWaiting().milliseconds(), TimeUnit.MILLISECONDS)); server.stop(); timing.sleepABit(); server.restart(); timing.sleepABit(); Assert.assertTrue(timing.awaitLatch(reconnectedLatch)); } finally { CloseableUtils.closeQuietly(client); } } @Test public void testNoServerAtStart() throws Exception { server.stop(); CuratorFramework client = CuratorFrameworkFactory.newClient(server.getConnectString(), timing.session(), timing.connection(), new RetryOneTime(1)); try { client.start(); PersistentEphemeralNode node = new PersistentEphemeralNode(client, PersistentEphemeralNode.Mode.EPHEMERAL, "/abc/node", "hello".getBytes()); node.start(); final CountDownLatch connectedLatch = new CountDownLatch(1); ConnectionStateListener listener = new ConnectionStateListener() { @Override public void stateChanged(CuratorFramework client, ConnectionState newState) { if (newState == ConnectionState.CONNECTED) { connectedLatch.countDown(); } } }; client.getConnectionStateListenable().addListener(listener); timing.sleepABit(); server.restart(); Assert.assertTrue(timing.awaitLatch(connectedLatch)); timing.sleepABit(); Assert.assertTrue(node.waitForInitialCreate(timing.forWaiting().milliseconds(), TimeUnit.MILLISECONDS)); } finally { CloseableUtils.closeQuietly(client); } } @Test(expectedExceptions = NullPointerException.class) public void testNullCurator() throws Exception { new PersistentEphemeralNode(null, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); } @Test(expectedExceptions = IllegalArgumentException.class) public void testNullPath() throws Exception { CuratorFramework curator = newCurator(); new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, null, new byte[0]); } @Test(expectedExceptions = NullPointerException.class) public void testNullData() throws Exception { CuratorFramework curator = newCurator(); new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, null); } @Test(expectedExceptions = NullPointerException.class) public void testNullMode() throws Exception { CuratorFramework curator = newCurator(); new PersistentEphemeralNode(curator, null, PATH, new byte[0]); } @Test public void testSettingDataSequential() throws Exception { setDataTest(PersistentEphemeralNode.Mode.EPHEMERAL_SEQUENTIAL); } @Test public void testSettingData() throws Exception { setDataTest(PersistentEphemeralNode.Mode.EPHEMERAL); } protected void setDataTest(PersistentEphemeralNode.Mode mode) throws Exception { PersistentEphemeralNode node = null; CuratorFramework client = CuratorFrameworkFactory.newClient(server.getConnectString(), timing.session(), timing.connection(), new RetryOneTime(1)); try { client.start(); node = new PersistentEphemeralNode(client, mode, PATH, "a".getBytes()); node.start(); Assert.assertTrue(node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS)); Assert.assertEquals(client.getData().forPath(node.getActualPath()), "a".getBytes()); final Semaphore semaphore = new Semaphore(0); Watcher watcher = new Watcher() { @Override public void process(WatchedEvent arg0) { semaphore.release(); } }; client.checkExists().usingWatcher(watcher).forPath(node.getActualPath()); node.setData("b".getBytes()); Assert.assertTrue(timing.acquireSemaphore(semaphore)); Assert.assertEquals(node.getActualPath(), node.getActualPath()); Assert.assertEquals(client.getData().usingWatcher(watcher).forPath(node.getActualPath()), "b".getBytes()); node.setData("c".getBytes()); Assert.assertTrue(timing.acquireSemaphore(semaphore)); Assert.assertEquals(node.getActualPath(), node.getActualPath()); Assert.assertEquals(client.getData().usingWatcher(watcher).forPath(node.getActualPath()), "c".getBytes()); node.close(); Assert.assertTrue(timing.acquireSemaphore(semaphore)); } finally { if (node != null) { node.close(); } client.close(); } } @Test public void testDeletesNodeWhenClosed() throws Exception { CuratorFramework curator = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); String path = null; try { node.waitForInitialCreate(5, TimeUnit.SECONDS); path = node.getActualPath(); assertNodeExists(curator, path); } finally { node.close(); // After closing the path is set to null... } assertNodeDoesNotExist(curator, path); } @Test public void testClosingMultipleTimes() throws Exception { CuratorFramework curator = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); String path = node.getActualPath(); node.close(); assertNodeDoesNotExist(curator, path); node.close(); assertNodeDoesNotExist(curator, path); } @Test public void testDeletesNodeWhenSessionDisconnects() throws Exception { CuratorFramework curator = newCurator(); CuratorFramework observer = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); assertNodeExists(observer, node.getActualPath()); // Register a watch that will fire when the node is deleted... Trigger deletedTrigger = Trigger.deleted(); observer.checkExists().usingWatcher(deletedTrigger).forPath(node.getActualPath()); killSession(curator); // Make sure the node got deleted assertTrue(deletedTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); } finally { node.close(); } } @Test public void testRecreatesNodeWhenSessionReconnects() throws Exception { CuratorFramework curator = newCurator(); CuratorFramework observer = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(5, TimeUnit.SECONDS); assertNodeExists(observer, node.getActualPath()); Trigger deletedTrigger = Trigger.deleted(); observer.checkExists().usingWatcher(deletedTrigger).forPath(node.getActualPath()); killSession(curator); // Make sure the node got deleted... assertTrue(deletedTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); // Check for it to be recreated... Trigger createdTrigger = Trigger.created(); Stat stat = observer.checkExists().usingWatcher(createdTrigger).forPath(node.getActualPath()); assertTrue(stat != null || createdTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); } finally { node.close(); } } @Test public void testRecreatesNodeWhenSessionReconnectsMultipleTimes() throws Exception { CuratorFramework curator = newCurator(); CuratorFramework observer = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); String path = node.getActualPath(); assertNodeExists(observer, path); // We should be able to disconnect multiple times and each time the node should be recreated. for (int i = 0; i < 5; i++) { Trigger deletionTrigger = Trigger.deleted(); observer.checkExists().usingWatcher(deletionTrigger).forPath(path); // Kill the session, thus cleaning up the node... killSession(curator); // Make sure the node ended up getting deleted... assertTrue(deletionTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); // Now put a watch in the background looking to see if it gets created... Trigger creationTrigger = Trigger.created(); Stat stat = observer.checkExists().usingWatcher(creationTrigger).forPath(path); assertTrue(stat != null || creationTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); } } finally { node.close(); } } @Test public void testRecreatesNodeWhenEphemeralOwnerSessionExpires() throws Exception { CuratorFramework curator = newCurator(); CuratorFramework nodeCreator = newCurator(); CuratorFramework observer = newCurator(); nodeCreator.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(PATH, new byte[0]); Trigger dataChangedTrigger = Trigger.dataChanged(); observer.getData().usingWatcher(dataChangedTrigger).forPath(PATH); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(5, TimeUnit.SECONDS); assertNodeExists(observer, node.getActualPath()); assertTrue(dataChangedTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); Trigger deletedTrigger = Trigger.deleted(); observer.checkExists().usingWatcher(deletedTrigger).forPath(node.getActualPath()); killSession(nodeCreator); // Make sure the node got deleted... assertTrue(deletedTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); // Check for it to be recreated... Trigger createdTrigger = Trigger.created(); Stat stat = observer.checkExists().usingWatcher(createdTrigger).forPath(node.getActualPath()); assertTrue(stat != null || createdTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); } finally { node.close(); } } @Test public void testRecreatesNodeWhenItGetsDeleted() throws Exception { CuratorFramework curator = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); String originalNode = node.getActualPath(); assertNodeExists(curator, originalNode); // Delete the original node... curator.delete().forPath(originalNode); // Since we're using an ephemeral node, and the original session hasn't been interrupted the name of the new // node that gets created is going to be exactly the same as the original. Trigger createdWatchTrigger = Trigger.created(); Stat stat = curator.checkExists().usingWatcher(createdWatchTrigger).forPath(originalNode); assertTrue(stat != null || createdWatchTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); } finally { node.close(); } } @Test public void testRecreatesNodeWhenItGetsDeletedAfterSetData() throws Exception { CuratorFramework curator = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); String originalNode = node.getActualPath(); assertNodeExists(curator, originalNode); Trigger dataChangedTrigger = Trigger.dataChanged(); curator.getData().usingWatcher(dataChangedTrigger).forPath(originalNode); // update the data of the node node.setData(new byte[0]); // wait for the data to be updated: assertTrue(dataChangedTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); // Delete the original node... curator.delete().forPath(originalNode); // Since we're using an ephemeral node, and the original session hasn't been interrupted the name of the new // node that gets created is going to be exactly the same as the original. Trigger createdWatchTrigger = Trigger.created(); Stat stat = curator.checkExists().usingWatcher(createdWatchTrigger).forPath(originalNode); assertTrue(stat != null || createdWatchTrigger.firedWithin(timing.forWaiting().seconds(), TimeUnit.SECONDS)); } finally { node.close(); } } @Test public void testNodesCreateUniquePaths() throws Exception { CuratorFramework curator = newCurator(); PersistentEphemeralNode node1 = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL_SEQUENTIAL, PATH, new byte[0]); node1.start(); try { node1.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); String path1 = node1.getActualPath(); PersistentEphemeralNode node2 = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL_SEQUENTIAL, PATH, new byte[0]); node2.start(); try { node2.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); String path2 = node2.getActualPath(); assertFalse(path1.equals(path2)); } finally { node2.close(); } } finally { node1.close(); } } @Test public void testData() throws Exception { CuratorFramework curator = newCurator(); byte[] data = "Hello World".getBytes(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, data); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), data)); } finally { node.close(); } } /** * Test that if a persistent ephemeral node is created and the node already exists * that if data is present in the PersistentEphermalNode that it is still set. * @throws Exception */ @Test public void testSetDataWhenNodeExists() throws Exception { CuratorFramework curator = newCurator(); curator.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(PATH, "InitialData".getBytes()); byte[] data = "Hello World".getBytes(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, data); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), data)); } finally { node.close(); } } @Test public void testSetDataWhenDisconnected() throws Exception { CuratorFramework curator = newCurator(); byte[] initialData = "Hello World".getBytes(); byte[] updatedData = "Updated".getBytes(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, initialData); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), initialData)); server.stop(); final CountDownLatch dataUpdateLatch = new CountDownLatch(1); Watcher watcher = new Watcher() { @Override public void process(WatchedEvent event) { if (event.getType() == EventType.NodeDataChanged) { dataUpdateLatch.countDown(); } } }; curator.getData().usingWatcher(watcher).inBackground().forPath(node.getActualPath()); node.setData(updatedData); server.restart(); assertTrue(timing.awaitLatch(dataUpdateLatch)); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), updatedData)); } finally { node.close(); } } @Test public void testSetUpdatedDataWhenReconnected() throws Exception { CuratorFramework curator = newCurator(); byte[] initialData = "Hello World".getBytes(); byte[] updatedData = "Updated".getBytes(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, initialData); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), initialData)); node.setData(updatedData); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), updatedData)); server.restart(); final CountDownLatch dataUpdateLatch = new CountDownLatch(1); curator.getData().inBackground(new BackgroundCallback() { @Override public void processResult(CuratorFramework client, CuratorEvent event) throws Exception { dataUpdateLatch.countDown(); } }).forPath(node.getActualPath()); assertTrue(timing.awaitLatch(dataUpdateLatch)); assertTrue(Arrays.equals(curator.getData().forPath(node.getActualPath()), updatedData)); } finally { node.close(); } } /** * See CURATOR-190 * For protected nodes on reconnect the current protected name was passed to the create builder meaning that it got * appended to the new protected node name. This meant that a new node got created on each reconnect. * @throws Exception */ @Test public void testProtected() throws Exception { CuratorFramework curator = newCurator(); PersistentEphemeralNode node = new PersistentEphemeralNode(curator, PersistentEphemeralNode.Mode.PROTECTED_EPHEMERAL, PATH, new byte[0]); node.start(); try { node.waitForInitialCreate(timing.forWaiting().seconds(), TimeUnit.SECONDS); assertNodeExists(curator, node.getActualPath()); server.restart(); curator.blockUntilConnected(5, TimeUnit.SECONDS); assertNodeExists(curator, node.getActualPath()); //There should only be a single child, the persisted ephemeral node List<String> children = curator.getChildren().forPath(DIR); assertFalse(children == null); assertEquals(children.size(), 1); } finally { node.close(); } } @Test public void testNoCreatePermission() throws Exception { CuratorFrameworkFactory.Builder builder = CuratorFrameworkFactory.builder(); CuratorFramework client = builder.connectString(server.getConnectString()) .authorization("digest", "me1:pass1".getBytes()).retryPolicy(new RetryOneTime(1)).build(); client.start(); ACL acl = new ACL(ZooDefs.Perms.WRITE, ZooDefs.Ids.AUTH_IDS); List<ACL> aclList = Lists.newArrayList(acl); client.create().withACL(aclList).forPath(DIR, new byte[0]); client.close(); PersistentEphemeralNode node = null; try { //New client without authentication client = newCurator(); node = new PersistentEphemeralNode(client, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); node.waitForInitialCreate(timing.seconds(), TimeUnit.SECONDS); assertNodeDoesNotExist(client, PATH); assertTrue(node.isAuthFailure()); } finally { if (node != null) { node.close(); } client.close(); } } @Test public void testNoWritePermission() throws Exception { final ACLProvider aclProvider = new ACLProvider() { final ACL acl = new ACL(ZooDefs.Perms.READ | ZooDefs.Perms.CREATE | ZooDefs.Perms.DELETE, ZooDefs.Ids.ANYONE_ID_UNSAFE); final List<ACL> aclList = Collections.singletonList(acl); @Override public List<ACL> getDefaultAcl() { return aclList; } @Override public List<ACL> getAclForPath(String path) { return aclList; } }; CuratorFrameworkFactory.Builder builder = CuratorFrameworkFactory.builder(); CuratorFramework client = builder.connectString(server.getConnectString()).aclProvider(aclProvider) .retryPolicy(new RetryOneTime(1)).build(); PersistentEphemeralNode node = null; try { client.start(); node = new PersistentEphemeralNode(client, PersistentEphemeralNode.Mode.EPHEMERAL, PATH, new byte[0]); node.start(); assertTrue(node.waitForInitialCreate(timing.seconds(), TimeUnit.SECONDS), "Node not created"); assertNodeExists(client, PATH); assertFalse(node.isAuthFailure(), "AuthFailure when creating node."); byte[] NEW_DATA = "NEW_DATA".getBytes(); node.setData(NEW_DATA); timing.sleepABit(); byte[] read_data = client.getData().forPath(PATH); assertNotEquals(read_data, NEW_DATA, "Data matches - write went through."); assertTrue(node.isAuthFailure(), "AuthFailure response not received."); } finally { CloseableUtils.closeQuietly(node); CloseableUtils.closeQuietly(client); } } private void assertNodeExists(CuratorFramework curator, String path) throws Exception { assertNotNull(path); assertTrue(curator.checkExists().forPath(path) != null); } private void assertNodeDoesNotExist(CuratorFramework curator, String path) throws Exception { assertTrue(curator.checkExists().forPath(path) == null); } private CuratorFramework newCurator() throws IOException { CuratorFramework client = CuratorFrameworkFactory.newClient(server.getConnectString(), timing.session(), timing.connection(), new RetryOneTime(1)); client.start(); curatorInstances.add(client); return client; } public void killSession(CuratorFramework curator) throws Exception { KillSession.kill(curator.getZookeeperClient().getZooKeeper(), curator.getZookeeperClient().getCurrentConnectionString()); } private static final class Trigger implements Watcher { private final Event.EventType type; private final CountDownLatch latch; public Trigger(Event.EventType type) { assertNotNull(type); this.type = type; this.latch = new CountDownLatch(1); } @Override public void process(WatchedEvent event) { if (type == event.getType()) { latch.countDown(); } } public boolean firedWithin(long duration, TimeUnit unit) { try { return latch.await(duration, unit); } catch (InterruptedException e) { throw Throwables.propagate(e); } } private static Trigger created() { return new Trigger(Event.EventType.NodeCreated); } private static Trigger deleted() { return new Trigger(Event.EventType.NodeDeleted); } private static Trigger dataChanged() { return new Trigger(EventType.NodeDataChanged); } } }