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.jclouds.examples.rackspace.cloudqueues; import com.google.common.collect.ImmutableList; import com.google.common.io.Closeables; import org.jclouds.ContextBuilder; import org.jclouds.openstack.marconi.v1.MarconiApi; import org.jclouds.openstack.marconi.v1.domain.CreateMessage; import org.jclouds.openstack.marconi.v1.domain.Message; import org.jclouds.openstack.marconi.v1.domain.MessageStream; import org.jclouds.openstack.marconi.v1.features.MessageApi; import org.jclouds.openstack.marconi.v1.features.QueueApi; import org.jclouds.openstack.marconi.v1.options.StreamMessagesOptions; import java.io.Closeable; import java.io.IOException; import java.io.StringReader; import java.util.List; import java.util.Properties; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import static java.lang.String.format; import static org.jclouds.examples.rackspace.cloudqueues.Constants.MESSAGE_NUM; import static org.jclouds.examples.rackspace.cloudqueues.Constants.MESSAGE_TEXT; import static org.jclouds.examples.rackspace.cloudqueues.Constants.NAME; import static org.jclouds.examples.rackspace.cloudqueues.Constants.NUM_THREADS; import static org.jclouds.examples.rackspace.cloudqueues.Constants.PROVIDER; import static org.jclouds.examples.rackspace.cloudqueues.Constants.PUBLISHER_ID; import static org.jclouds.examples.rackspace.cloudqueues.Constants.PUBLISHER_NAME; import static org.jclouds.examples.rackspace.cloudqueues.Constants.SUBSCRIBER_ID; import static org.jclouds.examples.rackspace.cloudqueues.Constants.REGION; import static org.jclouds.openstack.marconi.v1.options.StreamMessagesOptions.Builder.limit; /** * Characteristics of the Publish/Subscribe model in Cloud Queues are: * * 1. All subscribers listen to the messages on the queue. * 2. Messages are not claimed. * 3. Subscribers can send a marker/cursor to skip messages already seen. * 4. TTL deletes messages eventually. * * Ideal for notification of events to multiple listeners at once. */ public class PublishSubscribe implements Closeable { private final MarconiApi marconiApi; private final QueueApi queueApi; /** * To get a username and API key see * http://apache.jclouds.org/documentation/quickstart/rackspace/ * * The first argument (args[0]) must be your username * The second argument (args[1]) must be your API key */ public static void main(String[] args) throws IOException { PublishSubscribe publishSubscribe = new PublishSubscribe(args[0], args[1]); try { publishSubscribe.createQueue(); publishSubscribe.publishAndSubscribe(); publishSubscribe.deleteQueue(); } catch (Exception e) { e.printStackTrace(); } finally { publishSubscribe.close(); } } public PublishSubscribe(String username, String apiKey) { // If this application we're running *inside* the Rackspace Cloud, you would want to use the InternalUrlModule // as below to have all of the Cloud Queues traffic go over the internal Rackspace Cloud network. // Iterable<Module> modules = ImmutableSet.<Module> of(new InternalUrlModule()); marconiApi = ContextBuilder.newBuilder(PROVIDER).credentials(username, apiKey) // .modules(modules) .buildApi(MarconiApi.class); queueApi = marconiApi.getQueueApi(REGION, PUBLISHER_ID); } private void createQueue() { queueApi.create(NAME); } private void publishAndSubscribe() throws ExecutionException, InterruptedException { System.out.format("Publisher Subscriber%n"); ExecutorService executorService = Executors.newFixedThreadPool(NUM_THREADS); executorService.execute(new Subscriber("1")); executorService.execute(new Subscriber("2")); Future<?> publisherFuture = executorService.submit(new Publisher("1")); publisherFuture.get(); executorService.shutdown(); } private void deleteQueue() { queueApi.delete(NAME); } /** * Always close your service when you're done with it. * * Note that closing quietly like this is not necessary in Java 7. * You would use try-with-resources in the main method instead. */ public void close() throws IOException { Closeables.close(marconiApi, true); } private void sleep(long millis) { try { Thread.sleep(millis); } catch (InterruptedException e) { e.printStackTrace(); } } public class Publisher implements Runnable { private final String publisherName; private final MessageApi messageApi; protected Publisher(String publisherName) { this.publisherName = publisherName; messageApi = marconiApi.getMessageApi(REGION, PUBLISHER_ID, NAME); } public void run() { for (int i = 0; i < 32; i++) { messageApi.create(publish(i)); sleep(200); } } private List<CreateMessage> publish(int messageNum) { StringBuilder bodyBuilder = new StringBuilder(); bodyBuilder.append(format("%s=%s%n", PUBLISHER_NAME, publisherName)) .append(format("%s=%d%n", MESSAGE_NUM, messageNum)) .append(format("%s=%s%n", MESSAGE_TEXT, "Read all about it")); CreateMessage message = CreateMessage.builder().ttl(300).body(bodyBuilder.toString()).build(); System.out.format(" Publisher %s Message %s:%d%n", publisherName, publisherName, messageNum); return ImmutableList.of(message); } } public class Subscriber implements Runnable { private final String subscriberName; private final MessageApi messageApi; private int consecutiveSleepCount = 0; protected Subscriber(String subscriberName) { this.subscriberName = subscriberName; messageApi = marconiApi.getMessageApi(REGION, SUBSCRIBER_ID, NAME); } /** * Process messages off the queue until we haven't seen any messages 3 times in a row. */ public void run() { StreamMessagesOptions streamMessagesOptions = limit(2); MessageStream stream = messageApi.stream(streamMessagesOptions); while (consecutiveSleepCount < 3) { if (stream.nextMarker().isPresent()) { process(stream); consecutiveSleepCount = 0; streamMessagesOptions = stream.nextStreamOptions(); } else { sleep(150); consecutiveSleepCount++; // leave the streamMessagesOptions from the previous loop as is so it can be used in the next loop } stream = messageApi.stream(streamMessagesOptions); } } private void process(MessageStream messageStream) { for (Message message : messageStream) { Properties props = loadStringProperties(message.getBody()); System.out.format(" Subscriber %s Message %s:%s (%s)%n", subscriberName, props.getProperty(PUBLISHER_NAME), props.getProperty(MESSAGE_NUM), props.getProperty(MESSAGE_TEXT)); } } private Properties loadStringProperties(String body) { Properties properties = new Properties(); try { properties.load(new StringReader(body)); } catch (IOException e) { // IOException will never occur here because we're loading directly from a String } return properties; } } }