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Rabbitmq学习笔记

  • 分类:架构/云
  • 本文标签: RabbitMQ
  • 发布时间:2017-12-17 17:39:49
  • 查看数: 8

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。Ubuntu上也可以手动安装(sudo apt-get install rabbitmq-server)。
官网给的教程使用的pika连接。 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)

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()
python receiver.py
python send.py
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。

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