RabbitMQ的幾種典型使用場景

RabbitMQ主頁：https://www.rabbitmq.com/

學習RabbitMQ的使用場景，來自官方教程：https://www.rabbitmq.com/getstarted.html

場景1：單發送單接收

使用場景：簡單的發送與接收，沒有特別的處理。

Producer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; public class Send { private final static String QUEUE_NAME = "hello"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.queueDeclare(QUEUE_NAME, false, false, false, null); String message = "Hello World!"; channel.basicPublish("", QUEUE_NAME, null, message.getBytes()); System.out.println(" [x] Sent '" + message + "'"); channel.close(); connection.close(); } }

Consumer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.QueueingConsumer; public class Recv { private final static String QUEUE_NAME = "hello"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.queueDeclare(QUEUE_NAME, false, false, false, null); System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); QueueingConsumer consumer = new QueueingConsumer(channel); channel.basicConsume(QUEUE_NAME, true, consumer); while (true) { QueueingConsumer.Delivery delivery = consumer.nextDelivery(); String message = new String(delivery.getBody()); System.out.println(" [x] Received '" + message + "'"); } } }

場景2：單發送多接收

使用場景：一個發送端，多個接收端，如分佈式的任務派發。爲了保證消息發送的可靠性，不丟失消息，使消息持久化了。同時爲了防止接收端在處理消息時down掉，只有在消息處理完成後才發送ack消息。

Producer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.MessageProperties; public class NewTask { private static final String TASK_QUEUE_NAME = "task_queue"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.queueDeclare(TASK_QUEUE_NAME, true, false, false, null); String message = getMessage(argv); channel.basicPublish( "", TASK_QUEUE_NAME, MessageProperties.PERSISTENT_TEXT_PLAIN, message.getBytes()); System.out.println(" [x] Sent '" + message + "'"); channel.close(); connection.close(); } private static String getMessage(String[] strings){ if (strings.length < 1) return "Hello World!"; return joinStrings(strings, " "); } private static String joinStrings(String[] strings, String delimiter) { int length = strings.length; if (length == 0) return ""; StringBuilder words = new StringBuilder(strings[0]); for (int i = 1; i < length; i++) { words.append(delimiter).append(strings[i]); } return words.toString(); } }

發送端和場景1不一樣點：

一、使用「task_queue」聲明瞭另外一個Queue，由於RabbitMQ不允許聲明2個相同名稱、配置不一樣的Queue

二、使"task_queue"的Queue的durable的屬性爲true，即便消息隊列durable

三、使用MessageProperties.PERSISTENT_TEXT_PLAIN使消息durable

When RabbitMQ quits or crashes it will forget the queues and messages unless you tell it not to. Two things are required to make sure that messages aren't lost: we need to mark both the queue and messages as durable.

Consumer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.QueueingConsumer; public class Worker { private static final String TASK_QUEUE_NAME = "task_queue"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.queueDeclare(TASK_QUEUE_NAME, true, false, false, null); System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); channel.basicQos(1); QueueingConsumer consumer = new QueueingConsumer(channel); channel.basicConsume(TASK_QUEUE_NAME, false, consumer); while (true) { QueueingConsumer.Delivery delivery = consumer.nextDelivery(); String message = new String(delivery.getBody()); System.out.println(" [x] Received '" + message + "'"); doWork(message); System.out.println(" [x] Done"); channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false); } } private static void doWork(String task) throws InterruptedException { for (char ch: task.toCharArray()) { if (ch == '.') Thread.sleep(1000); } } }

接收端和場景1不一樣點：

一、使用「task_queue」聲明消息隊列，並使消息隊列durable

二、在使用channel.basicConsume接收消息時使autoAck爲false，即不自動會發ack，由channel.basicAck()在消息處理完成後發送消息。

三、使用了channel.basicQos(1)保證在接收端一個消息沒有處理完時不會接收另外一個消息，即接收端發送了ack後纔會接收下一個消息。在這種狀況下發送端會嘗試把消息發送給下一個not busy的接收端。

注意點：

1）It's a common mistake to miss the basicAck. It's an easy error, but the consequences are serious. Messages will be redelivered when your client quits (which may look like random redelivery), but RabbitMQ will eat more and more memory as it won't be able to release any unacked messages.

2）Note on message persistence

Marking messages as persistent doesn't fully guarantee that a message won't be lost. Although it tells RabbitMQ to save the message to disk, there is still a short time window when RabbitMQ has accepted a message and hasn't saved it yet. Also, RabbitMQ doesn't do fsync(2) for every message -- it may be just saved to cache and not really written to the disk. The persistence guarantees aren't strong, but it's more than enough for our simple task queue. If you need a stronger guarantee you can wrap the publishing code in atransaction.

3）Note about queue size

If all the workers are busy, your queue can fill up. You will want to keep an eye on that, and maybe add more workers, or have some other strategy.

場景3：Publish/Subscribe

使用場景：發佈、訂閱模式，發送端發送廣播消息，多個接收端接收。

Producer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; public class EmitLog { private static final String EXCHANGE_NAME = "logs"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.exchangeDeclare(EXCHANGE_NAME, "fanout"); String message = getMessage(argv); channel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes()); System.out.println(" [x] Sent '" + message + "'"); channel.close(); connection.close(); } private static String getMessage(String[] strings){ if (strings.length < 1) return "info: Hello World!"; return joinStrings(strings, " "); } private static String joinStrings(String[] strings, String delimiter) { int length = strings.length; if (length == 0) return ""; StringBuilder words = new StringBuilder(strings[0]); for (int i = 1; i < length; i++) { words.append(delimiter).append(strings[i]); } return words.toString(); } }

發送端：

發送消息到一個名爲「logs」的exchange上，使用「fanout」方式發送，即廣播消息，不須要使用queue，發送端不須要關心誰接收。

Consumer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.QueueingConsumer; public class ReceiveLogs { private static final String EXCHANGE_NAME = "logs"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.exchangeDeclare(EXCHANGE_NAME, "fanout"); String queueName = channel.queueDeclare().getQueue(); channel.queueBind(queueName, EXCHANGE_NAME, ""); System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); QueueingConsumer consumer = new QueueingConsumer(channel); channel.basicConsume(queueName, true, consumer); while (true) { QueueingConsumer.Delivery delivery = consumer.nextDelivery(); String message = new String(delivery.getBody()); System.out.println(" [x] Received '" + message + "'"); } } }

接收端：

一、聲明名爲「logs」的exchange的，方式爲"fanout"，和發送端同樣。

二、channel.queueDeclare().getQueue();該語句獲得一個隨機名稱的Queue，該queue的類型爲non-durable、exclusive、auto-delete的，將該queue綁定到上面的exchange上接收消息。

三、注意binding queue的時候，channel.queueBind()的第三個參數Routing key爲空，即全部的消息都接收。若是這個值不爲空，在exchange type爲「fanout」方式下該值被忽略！

場景4：Routing (按路線發送接收)

使用場景：發送端按routing key發送消息，不一樣的接收端按不一樣的routing key接收消息。

Producer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; public class EmitLogDirect { private static final String EXCHANGE_NAME = "direct_logs"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.exchangeDeclare(EXCHANGE_NAME, "direct"); String severity = getSeverity(argv); String message = getMessage(argv); channel.basicPublish(EXCHANGE_NAME, severity, null, message.getBytes()); System.out.println(" [x] Sent '" + severity + "':'" + message + "'"); channel.close(); connection.close(); } private static String getSeverity(String[] strings){ if (strings.length < 1) return "info"; return strings[0]; } private static String getMessage(String[] strings){ if (strings.length < 2) return "Hello World!"; return joinStrings(strings, " ", 1); } private static String joinStrings(String[] strings, String delimiter, int startIndex) { int length = strings.length; if (length == 0 ) return ""; if (length < startIndex ) return ""; StringBuilder words = new StringBuilder(strings[startIndex]); for (int i = startIndex + 1; i < length; i++) { words.append(delimiter).append(strings[i]); } return words.toString(); } }

發送端和場景3的區別：

一、exchange的type爲direct

二、發送消息的時候加入了routing key

Consumer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.QueueingConsumer; public class ReceiveLogsDirect { private static final String EXCHANGE_NAME = "direct_logs"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.exchangeDeclare(EXCHANGE_NAME, "direct"); String queueName = channel.queueDeclare().getQueue(); if (argv.length < 1){ System.err.println("Usage: ReceiveLogsDirect [info] [warning] [error]"); System.exit(1); } for(String severity : argv){ channel.queueBind(queueName, EXCHANGE_NAME, severity); } System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); QueueingConsumer consumer = new QueueingConsumer(channel); channel.basicConsume(queueName, true, consumer); while (true) { QueueingConsumer.Delivery delivery = consumer.nextDelivery(); String message = new String(delivery.getBody()); String routingKey = delivery.getEnvelope().getRoutingKey(); System.out.println(" [x] Received '" + routingKey + "':'" + message + "'"); } } }

接收端和場景3的區別：

在綁定queue和exchange的時候使用了routing key，即從該exchange上只接收routing key指定的消息。

場景5：Topics (按topic發送接收)

使用場景：發送端不僅按固定的routing key發送消息，而是按字符串「匹配」發送，接收端一樣如此。

Producer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; public class EmitLogTopic { private static final String EXCHANGE_NAME = "topic_logs"; public static void main(String[] argv) { Connection connection = null; Channel channel = null; try { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); connection = factory.newConnection(); channel = connection.createChannel(); channel.exchangeDeclare(EXCHANGE_NAME, "topic"); String routingKey = getRouting(argv); String message = getMessage(argv); channel.basicPublish(EXCHANGE_NAME, routingKey, null, message.getBytes()); System.out.println(" [x] Sent '" + routingKey + "':'" + message + "'"); } catch (Exception e) { e.printStackTrace(); } finally { if (connection != null) { try { connection.close(); } catch (Exception ignore) {} } } } private static String getRouting(String[] strings){ if (strings.length < 1) return "anonymous.info"; return strings[0]; } private static String getMessage(String[] strings){ if (strings.length < 2) return "Hello World!"; return joinStrings(strings, " ", 1); } private static String joinStrings(String[] strings, String delimiter, int startIndex) { int length = strings.length; if (length == 0 ) return ""; if (length < startIndex ) return ""; StringBuilder words = new StringBuilder(strings[startIndex]); for (int i = startIndex + 1; i < length; i++) { words.append(delimiter).append(strings[i]); } return words.toString(); } }

發送端和場景4的區別：

一、exchange的type爲topic

二、發送消息的routing key不是固定的單詞，而是匹配字符串，如"*.lu.#"，*匹配一個單詞，#匹配0個或多個單詞。

Consumer：

import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.QueueingConsumer; public class ReceiveLogsTopic { private static final String EXCHANGE_NAME = "topic_logs"; public static void main(String[] argv) { Connection connection = null; Channel channel = null; try { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); connection = factory.newConnection(); channel = connection.createChannel(); channel.exchangeDeclare(EXCHANGE_NAME, "topic"); String queueName = channel.queueDeclare().getQueue(); if (argv.length < 1){ System.err.println("Usage: ReceiveLogsTopic [binding_key]..."); System.exit(1); } for(String bindingKey : argv){ channel.queueBind(queueName, EXCHANGE_NAME, bindingKey); } System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); QueueingConsumer consumer = new QueueingConsumer(channel); channel.basicConsume(queueName, true, consumer); while (true) { QueueingConsumer.Delivery delivery = consumer.nextDelivery(); String message = new String(delivery.getBody()); String routingKey = delivery.getEnvelope().getRoutingKey(); System.out.println(" [x] Received '" + routingKey + "':'" + message + "'"); } } catch (Exception e) { e.printStackTrace(); } finally { if (connection != null) { try { connection.close(); } catch (Exception ignore) {} } } } }

接收端和場景4的區別：

一、exchange的type爲topic

二、接收消息的routing key不是固定的單詞，而是匹配字符串。

注意點：

Topic exchange

Topic exchange is powerful and can behave like other exchanges. When a queue is bound with "#" (hash) binding key - it will receive all the messages, regardless of the routing key - like in fanout exchange. When special characters "*" (star) and "#" (hash) aren't used in bindings, the topic exchange will behave just like a direct one.

 

參考：https://www.rabbitmq.com/getstarted.html