虚拟化|Rabbitmq学习笔记中间件技术|openstack

【虚拟化|Rabbitmq学习笔记】1，基本概念

RabbitMQ是流行的开源消息队列系统，用erlang语言开发。我曾经对这门语言挺有兴趣，学过一段时间，后来没坚持。 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。 2，环境搭建因为最经工作在 Openstack的开发上，所以我直接在ubuntu上使用 devstack安装的 RabbitMQ。Ubuntu上也可以手动安装 RabbitMQ（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。 3，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）

文章图片

receiver.py

#!/usr/bin/env python import pikacredentials = 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 pikacredentials = 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()

python receiver.py python send.py 3.2 工作队列

文章图片

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 pikacredentials = 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 pikacredentials = 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

文章图片

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 pikacredentials = 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 pikacredentials = 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.queuechannel.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

文章图片

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 pikacredentials = 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 pikacredentials = 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

文章图片

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 syscredentials = 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 syscredentials = 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.queuebinding_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

文章图片

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 uuidclass 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.queueself.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 = bodydef 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 pikacredentials = 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()