概述

RabbitMQ 是一个开源的消息代理和队列服务器，它实现了 AMQP (Advanced Message Queuing Protocol) 1.0 标准。RabbitMQ 可以在多语言环境中作为中间件处理应用程序之间的消息传递。

本教程将带你从零开始学习如何使用 RabbitMQ 进行消息的发布与订阅。

环境准备

1. 安装 RabbitMQ

- [官方文档](https://www.rabbitmq.com/download.html) 提供了多种平台的安装指南。

2. 安装 Erlang

- RabbitMQ 基于 Erlang 开发，需要先安装 Erlang。

3. 安装客户端库

- 选择一种编程语言并安装相应的客户端库（例如 Python、Java）。

第一步：启动 RabbitMQ 服务

```bash

rabbitmq-server

```

第二步：创建用户和权限

```bash

rabbitmqctl add_user guest guest

rabbitmqctl set_permissions -p / guest ".*" ".*" ".*"

```

第三步：访问管理控制台

- 访问 http://localhost:15672/ （默认用户名和密码都是 `guest`）

基础概念

- Exchange (交换器): 决定消息发送到哪里。

- Queue (队列): 存储消息的地方。

- Binding: Exchange 和 Queue 之间的连接。

- Routing Key: Exchange 使用它来决定消息发送给哪个 Queue。

示例：Hello World

1. 发布者 (Publisher)

Python 代码

```python

import pika

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))

channel = connection.channel()

channel.queue_declare(queue='hello')

channel.basic_publish(exchange='',

routing_key='hello',

body='Hello World!')

print(" [x] Sent 'Hello World!'")

connection.close()

```

2. 消费者 (Consumer)

Python 代码

```python

import pika

def callback(ch, method, properties, body):

print(" [x] Received %r" % body)

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))

channel = connection.channel()

channel.queue_declare(queue='hello')

channel.basic_consume(queue='hello',

on_message_callback=callback,

auto_ack=True)

print(' [*] Waiting for messages. To exit press CTRL+C')

channel.start_consuming()

```

示例：工作队列

1. 发送任务

Python 代码

```python

import pika

import sys

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))

channel = connection.channel()

channel.queue_declare(queue='task_queue', durable=True)

message = ' '.join(sys.argv[1:]) or "Hello World!"

channel.basic_publish(

exchange='',

routing_key='task_queue',

body=message,

properties=pika.BasicProperties(

delivery_mode=2, # make message persistent

))

print(" [x] Sent %r" % message)

connection.close()

```

2. 处理任务

Python 代码

```python

import pika

import time

def callback(ch, method, properties, body):

print(" [x] Received %r" % body)

time.sleep(body.count(b'.'))

print(" [x] Done")

ch.basic_ack(delivery_tag=method.delivery_tag)

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))

channel = connection.channel()

channel.queue_declare(queue='task_queue', durable=True)

print(' [*] Waiting for messages. To exit press CTRL+C')

channel.basic_qos(prefetch_count=1)

channel.basic_consume(queue='task_queue', on_message_callback=callback)

channel.start_consuming()

```

示例：发布/订阅模式

1. 发布消息

Python 代码

```python

import pika

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))

channel = connection.channel()

channel.exchange_declare(exchange='logs', exchange_type='fanout')

message = "Info: Hello from the publisher"

channel.basic_publish(exchange='logs', routing_key='', body=message)

print(" [x] Sent %r" % message)

connection.close()

```

2. 订阅消息

Python 代码

```python

import pika

import sys

def callback(ch, method, properties, body):

print(" [x] %r" % body)

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))

channel = connection.channel()

channel.exchange_declare(exchange='logs', exchange_type='fanout')

result = channel.queue_declare(queue='', exclusive=True)

queue_name = result.method.queue

channel.queue_bind(exchange='logs', queue=queue_name)

print(' [*] Waiting for logs. To exit press CTRL+C')

channel.basic_consume(

queue=queue_name, on_message_callback=callback, auto_ack=True)

channel.start_consuming()