Rabbitmq学习笔记

RabbitMQ是AMQP（高级消息队列协议）的标准实现。如果不熟悉AMQP，直接看RabbitMQ的文档会比较困难。不过它也只有几个关键概念，这里简单介绍。

几个概念说明：

Broker：简单来说就是消息队列服务器实体。
Exchange：消息交换机，它指定消息按什么规则，路由到哪个队列。
Queue：消息队列载体，每个消息都会被投入到一个或多个队列。
Binding：绑定，它的作用就是把exchange和queue按照路由规则绑定起来。
Routing Key：路由关键字，exchange根据这个关键字进行消息投递。
vhost：虚拟主机，一个broker里可以开设多个vhost，用作不同用户的权限分离。
producer：消息生产者，就是投递消息的程序。
consumer：消息消费者，就是接受消息的程序。
channel：消息通道，在客户端的每个连接里，可建立多个channel，每个channel代表一个会话任务。

消息队列的使用过程大概如下：

   （1）客户端连接到消息队列服务器，打开一个channel。

（2）客户端声明一个exchange，并设置相关属性。

（3）客户端声明一个queue，并设置相关属性。

（4）客户端使用routing key，在exchange和queue之间建立好绑定关系。

（5）客户端投递消息到exchange。

exchange接收到消息后，就根据消息的key和已经设置的binding，进行消息路由，将消息投递到一个或多个队列里。

exchange也有几个类型，完全根据key进行投递的叫做Direct交换机，

例如，绑定时设置了routing key为”abc”，那么客户端提交的消息，只有设置了key为”abc”的才会投递到队列。

对key进行模式匹配后进行投递的叫做Topic交换机，符号”#”匹配一个或多个词，符号”*”匹配正好一个词。

例如”abc.#”匹配”abc.def.ghi”，”abc.*”只匹配”abc.def”。还有一种不需要key的，叫做Fanout交换机，它采取广播模式，一个消息进来时，投递到与该交换机绑定的所有队列。

RabbitMQ支持消息的持久化，也就是数据写在磁盘上，为了数据安全考虑，我想大多数用户都会选择持久化。消息队列持久化包括3个部分：

（1）exchange持久化，在声明时指定durable => 1
（2）queue持久化，在声明时指定durable => 1
（3）消息持久化，在投递时指定delivery_mode => 2（1是非持久化）

如果exchange和queue都是持久化的，那么它们之间的binding也是持久化的。如果exchange和queue两者之间有一个持久化，一个非持久化，就不允许建立绑定。

环境搭建

ubuntu

sudo apt-get install rabbitmq-server

RabbitMQ官网给的教程使用的pika连接RabbitMQ。 Devstack 默认的是用kombu连接RabbitMQ。所以先要安装pika。

sudo apt-get install python-pip git-core
sudo pip install pika==0.9.8

环境搭建起来后就可以按照教程试验了。

实例教程

3.1 生产/消费者

最简单的示例，先尝试发送一个message给接受者（这里的例子和官网教程有点差别，设置连接参数和官网不同，因为devstack默认安装的Rabbitmq时修改了guest的密码为nova）

receiver.py

#!/usr/bin/env python  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials    )  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.queue_declare(queue='hello')  

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

def callback(ch, method, properties, body):  
    print " [x] Received %r" % (body,)  

channel.basic_consume(callback,  
                      queue='hello',  
                      no_ack=True)  

channel.start_consuming()

send.py

#!/usr/bin/env python  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
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()

3.2 工作队列

生产者生产消息，放入由routing_key指定的队列。消费者绑定该queue消费message。

new_task.py

#!/usr/bin/env python  
import sys  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
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()

worker.py

#!/usr/bin/env python  
import time  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials    )  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.queue_declare(queue='task_queue', durable=True)  
print ' [*] Waiting for messages. To exit press CTRL+C'  

def callback(ch, method, properties, body):  
    print " [x] Received %r" % (body,)  
    time.sleep( body.count('.') )  
    print " [x] Done"  
    ch.basic_ack(delivery_tag = method.delivery_tag)  

channel.basic_qos(prefetch_count=1)  
channel.basic_consume(callback,  
                      queue='task_queue')  

channel.start_consuming()

shell1$ python worker.py
 [*] Waiting for messages. To exit press CTRL+C
shell2$ python worker.py
 [*] Waiting for messages. To exit press CTRL+C
shell3$ python new_task.py First message.
shell3$ python new_task.py Second message..
shell3$ python new_task.py Third message...
shell3$ python new_task.py Fourth message....
shell3$ python new_task.py Fifth message.....

3.2 发布订阅

发送者发送消息到制定的exchange，接受者绑定队列到exchange接受消息

emit_log.py

#!/usr/bin/env python  
import sys  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

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

message = ' '.join(sys.argv[1:]) or "info: Hello World!"  
channel.basic_publish(exchange='logs',  
                      routing_key='',  
                      body=message)  
print " [x] Sent %r" % (message,)  
connection.close()

receive_log.py

#!/usr/bin/env python  
import time  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials    )  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

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

result = channel.queue_declare(exclusive=True)  
queue_name = result.method.queue  

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

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

def callback(ch, method, properties, body):  
    print " [x] %r" % (body,)  

channel.basic_consume(callback,  
                      queue=queue_name,  
                      no_ack=True)  

channel.start_consuming()

$ python emit_log.py
$ python receive_logs.py

3.2 消息路由

发送者不但可以指定消息的exchange，还可以指定消息的routing_key。进一步增加了消息投递的灵活性。

emit_logs_direct.py

#!/usr/bin/env python  
import sys  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.exchange_declare(exchange='direct_logs',  
                         type='direct')  
severity = sys.argv[1] if len(sys.argv) > 1 else 'info'  
message = ' '.join(sys.argv[2:]) or "info: Hello World!"  
channel.basic_publish(exchange='direct_logs',  
                      routing_key=severity,  
                      body=message)  
print " [x] Sent %r:%r" % (severity,message)  
connection.close()

receive_logs_direct.py

#!/usr/bin/env python  
import sys  
import time  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials    )  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.exchange_declare(exchange='direct_logs',  
                         type='direct')  

result = channel.queue_declare(exclusive=True)  
queue_name = result.method.queue  
severities = sys.argv[1:]  
if not severities:  
    print >> sys.stderr, "Usage: %s [info] [warning] [error]" % \  
                         (sys.argv[0],)  
    sys.exit(1)  

for severity in severities:  
    channel.queue_bind(exchange='direct_logs',  
                       queue=queue_name,  
                       routing_key=severity)  

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

def callback(ch, method, properties, body):  
    print " [x] %r:%r" % (method.routing_key, body,)  

channel.basic_consume(callback,  
                      queue=queue_name,  
                      no_ack=True)  

channel.start_consuming()

$ python receive_logs_direct.py info warning error
 [*] Waiting for logs. To exit press CTRL+C
$ python emit_log_direct.py error "Run. Run. Or it will explode."
 [x] Sent 'error':'Run. Run. Or it will explode.'

3.2 Topics

比exchange+routing_key更加灵活，routing_key可以支持通配符。

emit_logs_topic.py

#!/usr/bin/env python  
import pika  
import sys  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.exchange_declare(exchange='topic_logs',  
                         type='topic')  

routing_key = sys.argv[1] if len(sys.argv) > 1 else 'anonymous.info'  
message = ' '.join(sys.argv[2:]) or 'Hello World!'  
channel.basic_publish(exchange='topic_logs',  
                      routing_key=routing_key,  
                      body=message)  
print " [x] Sent %r:%r" % (routing_key, message)  
connection.close()

receive_logs_topic.py

#!/usr/bin/env python  
import pika  
import sys  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.exchange_declare(exchange='topic_logs',  
                         type='topic')  

result = channel.queue_declare(exclusive=True)  
queue_name = result.method.queue  

binding_keys = sys.argv[1:]  
if not binding_keys:  
    print >> sys.stderr, "Usage: %s [binding_key]..." % (sys.argv[0],)  
    sys.exit(1)  

for binding_key in binding_keys:  
    channel.queue_bind(exchange='topic_logs',  
                       queue=queue_name,  
                       routing_key=binding_key)  

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

def callback(ch, method, properties, body):  
    print " [x] %r:%r" % (method.routing_key, body,)  

channel.basic_consume(callback,  
                      queue=queue_name,  
                      no_ack=True)  

channel.start_consuming()

python emit_log_topic.py "kern.critical" "A critical kernel error"
python receive_logs_topic.py "kern.*" "*.critical"

3.2 远程过程调用

直接从一个进程调用另外一个进程。

rpc_client.py

#!/usr/bin/env python  
import pika  
import uuid  

class FibonacciRpcClient(object):  
    def __init__(self):  
        credentials = pika.PlainCredentials('guest', 'nova')  
        parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
        self.connection = pika.BlockingConnection(parameters)  
        self.channel = self.connection.channel()  

        result = self.channel.queue_declare(exclusive=True)  
        self.callback_queue = result.method.queue  

        self.channel.basic_consume(self.on_response, no_ack=True,  
                                   queue=self.callback_queue)  

    def on_response(self, ch, method, props, body):  
        if self.corr_id == props.correlation_id:  
            self.response = body  

    def call(self, n):  
        self.response = None  
        self.corr_id = str(uuid.uuid4())  
        self.channel.basic_publish(exchange='',  
                                   routing_key='rpc_queue',  
                                   properties=pika.BasicProperties(  
                                         reply_to = self.callback_queue,  
                                         correlation_id = self.corr_id,  
                                         ),  
                                   body=str(n))  
        while self.response is None:  
            self.connection.process_data_events()  
        return int(self.response)  

fibonacci_rpc = FibonacciRpcClient()  

print " [x] Requesting fib(30)"  
response = fibonacci_rpc.call(30)  
print " [.] Got %r" % (response,)

rpc_server.py

#!/usr/bin/env python  
import pika  

credentials = pika.PlainCredentials('guest', 'nova')  
parameters = pika.ConnectionParameters('localhost',5672,'/',credentials)  
connection = pika.BlockingConnection(parameters)  
channel = connection.channel()  

channel.queue_declare(queue='rpc_queue')  

def fib(n):  
    if n == 0:  
        return 0  
    elif n == 1:  
        return 1  
    else:  
        return fib(n-1) + fib(n-2)  

def on_request(ch, method, props, body):  
    n = int(body)  

    print " [.] fib(%s)"  % (n,)  
    response = fib(n)  

    ch.basic_publish(exchange='',  
                     routing_key=props.reply_to,  
                     properties=pika.BasicProperties(correlation_id = \  
                                                     props.correlation_id),  
                     body=str(response))  
    ch.basic_ack(delivery_tag = method.delivery_tag)  

channel.basic_qos(prefetch_count=1)  
channel.basic_consume(on_request, queue='rpc_queue')  

print " [x] Awaiting RPC requests"  
channel.start_consuming()

$ python rpc_server.py
 [x] Awaiting RPC requests
$ python rpc_client.py
 [x] Requesting fib(30)

3,结束

Rabbitmq的topics方式，远程过程调用方式在openstack的源码中大量使用，如果不理解这几种方式，理解openstack源码还是比较费力的。

kombu的例子直接在kombu官网可以找到，在devstack环境可以直接跑。这里就不列了。