RabbitMQ广播：direct模式

一、

消息的广播需要exchange：exchange是一个转发器，其实把消息发给RabbitMQ里的exchange

fanout: 所有bind到此exchange的queue都可以接收消息，广播

direct: 通过routingKey和exchange决定的那个唯一的queue可以接收消息

topic:所有符合routingKey(此时可以是一个表达式)的routingKey所bind的queue可以接收消息

headers：通过headers来决定把消息发给哪些queue，用的比较少

原理：消息发布端分别发送INFO，WARNING，ERROR类型的消息，C1 C2 C3订阅了不同类型的消息

消息发送端：

'''
发布者publisher
'''
import pika
import sys

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs',
                         type='direct')  # 1、改成type='direct'
# 2、默认发送的消息级别为info，可以带参数，warning error等
severity = sys.argv[1] if len(sys.argv) > 1 else "info"

message = ' '.join(sys.argv[2:]) or " Hello World!"
channel.basic_publish(exchange='direct_logs',
                      routing_key=severity, # 3、把上面的消息发到这个queue中
                      body=message)
print("send :", message)
connection.close()

消息订阅者：

'''
订阅者subscriber
'''
import pika
import sys

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs',
                         type='direct')  # 4、改exchange的类型
result = channel.queue_declare(exclusive=True)
queue_name = result.method.queue

# 5、启动订阅端的时候，severities存放订阅端订阅了哪些级别
#    然后用routing_key把这些级别绑定到queue上，这些queue就放这些级别的消息
severities = sys.argv[1]
if not severities:
    sys.stderr.write("Usage: %s [info] [warning] [error]\n" % sys.argv[0])
    sys.exit(1)
for severity in severities:
    channel.queue_bind(exchange='direct_logs',
                       queue=queue_name,
                       routing_key=severity)
print("Wait for logs...")
# 6、使用method.routing_key可以得到消息的级别
def callback(ch, method, properties, body):
    print("received:", method.routing_key, body)
channel.basic_consume(callback,
                      queue=queue_name,
                      no_ack=True)
channel.start_consuming()

运行过程：

'''
启动订阅者1： python subscriber.py info
启动订阅者2：python subscriber.py info error
启动发布者1：python publisher.py info hello
启动发布者2：python publisher.py error  servicesdown
订阅者1收到消息：info b'hello'
订阅者2收到消息：info b'hello'    error b'servicesdown'
'''