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.twill.internal.state; import com.google.common.base.Charsets; import com.google.common.base.Joiner; import com.google.common.base.Preconditions; import com.google.common.base.Suppliers; import com.google.common.util.concurrent.AbstractIdleService; import com.google.common.util.concurrent.FutureCallback; import com.google.common.util.concurrent.Futures; import com.google.common.util.concurrent.Service; import com.google.gson.Gson; import com.google.gson.JsonElement; import com.google.gson.JsonObject; import org.apache.twill.api.RunId; import org.apache.twill.internal.RunIds; import org.apache.twill.internal.ZKServiceDecorator; import org.apache.twill.internal.zookeeper.InMemoryZKServer; import org.apache.twill.zookeeper.NodeData; import org.apache.twill.zookeeper.ZKClientService; import org.apache.twill.zookeeper.ZKClients; import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.data.Stat; import org.junit.Assert; import org.junit.Test; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.util.concurrent.ExecutionException; import java.util.concurrent.Semaphore; import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeoutException; import java.util.concurrent.atomic.AtomicReference; /** * */ public class ZKServiceDecoratorTest { private static final Logger LOG = LoggerFactory.getLogger(ZKServiceDecoratorTest.class); @Test public void testStateTransition() throws InterruptedException, ExecutionException, TimeoutException { InMemoryZKServer zkServer = InMemoryZKServer.builder().build(); zkServer.startAndWait(); try { final String namespace = Joiner.on('/').join("/twill", RunIds.generate(), "runnables", "Runner1"); final ZKClientService zkClient = ZKClientService.Builder.of(zkServer.getConnectionStr()).build(); zkClient.startAndWait(); zkClient.create(namespace, null, CreateMode.PERSISTENT).get(); try { JsonObject content = new JsonObject(); content.addProperty("containerId", "container-123"); content.addProperty("host", "localhost"); RunId runId = RunIds.generate(); final Semaphore semaphore = new Semaphore(0); ZKServiceDecorator service = new ZKServiceDecorator(ZKClients.namespace(zkClient, namespace), runId, Suppliers.ofInstance(content), new AbstractIdleService() { @Override protected void startUp() throws Exception { Preconditions.checkArgument(semaphore.tryAcquire(5, TimeUnit.SECONDS), "Fail to start"); } @Override protected void shutDown() throws Exception { Preconditions.checkArgument(semaphore.tryAcquire(5, TimeUnit.SECONDS), "Fail to stop"); } }); final String runnablePath = namespace + "/" + runId.getId(); final AtomicReference<String> stateMatch = new AtomicReference<String>("STARTING"); watchDataChange(zkClient, runnablePath + "/state", semaphore, stateMatch); Assert.assertEquals(Service.State.RUNNING, service.start().get(5, TimeUnit.SECONDS)); stateMatch.set("STOPPING"); Assert.assertEquals(Service.State.TERMINATED, service.stop().get(5, TimeUnit.SECONDS)); } finally { zkClient.stopAndWait(); } } finally { zkServer.stopAndWait(); } } private void watchDataChange(final ZKClientService zkClient, final String path, final Semaphore semaphore, final AtomicReference<String> stateMatch) { Futures.addCallback(zkClient.getData(path, new Watcher() { @Override public void process(WatchedEvent event) { if (event.getType() == Event.EventType.NodeDataChanged) { watchDataChange(zkClient, path, semaphore, stateMatch); } } }), new FutureCallback<NodeData>() { @Override public void onSuccess(NodeData result) { String content = new String(result.getData(), Charsets.UTF_8); JsonObject json = new Gson().fromJson(content, JsonElement.class).getAsJsonObject(); if (stateMatch.get().equals(json.get("state").getAsString())) { semaphore.release(); } } @Override public void onFailure(Throwable t) { exists(); } private void exists() { Futures.addCallback(zkClient.exists(path, new Watcher() { @Override public void process(WatchedEvent event) { if (event.getType() == Event.EventType.NodeCreated) { watchDataChange(zkClient, path, semaphore, stateMatch); } } }), new FutureCallback<Stat>() { @Override public void onSuccess(Stat result) { if (result != null) { watchDataChange(zkClient, path, semaphore, stateMatch); } } @Override public void onFailure(Throwable t) { LOG.error(t.getMessage(), t); } }); } }); } }