上篇文章中，我們構建了一個簡單的日誌系統。接下來，我們將豐富它：能夠使用不同的severity來監聽不同等級的log。比如我們希望只有error的log才儲存到磁碟上。
1. Bindings繫結
上篇文章中我們是這麼做的繫結：
channel.queue_bind(exchange=exchange_name,
queue=queue_name)複製程式碼繫結其實就是關聯了exchange和queue。或者這麼說：queue對exchagne的內容感興趣，exchange要把它的Message deliver到queue中。
實際上，繫結可以帶routing_key 這個引數。其實這個引數的名稱和basic_publish 的引數名是相同了。為了避免混淆，我們把它成為binding key。
使用一個key來建立binding :
channel.queue_bind(exchange=exchange_name,
queue=queue_name,
routing_key='black')複製程式碼對於fanout的exchange來說，這個引數是被忽略的。
2. Direct exchange
Direct exchange的路由演算法非常簡單：通過binding key的完全匹配，可以通過下圖來說明。
exchange X和兩個queue繫結在一起。Q1的binding key是orange。Q2的binding key是black和green。
當P publish key是orange時，exchange會把它放到Q1。如果是black或者green那麼就會到Q2。其餘的Message都會被丟棄。
3. Multiple bindings
4. Emitting logs
首先是我們要建立一個direct的exchange：
channel.exchange_declare(exchange='direct_logs',
type='direct')複製程式碼我們將使用log的severity作為routing key，這樣Consumer可以針對不同severity的log進行不同的處理。
publish：
channel.basic_publish(exchange='direct_logs',
routing_key=severity,
body=message)複製程式碼我們使用三種severity：’info’, ‘warning’, ‘error’.
5. Subscribing
對於queue，我們需要繫結severity：
result = channel.queue_declare(exclusive=True)
queue_name = result.method.queue
for severity in severities:
channel.queue_bind(exchange='direct_logs',
queue=queue_name,
routing_key=severity)複製程式碼
6. 最終版本
The code for emit_log_direct.py:
#!/usr/bin/env python
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(
host='localhost'))
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 'Hello World!'
channel.basic_publish(exchange='direct_logs',
routing_key=severity,
body=message)
print " [x] Sent %r:%r" % (severity, message)
connection.close()複製程式碼The code for receive_logs_direct.py:
#!/usr/bin/env python
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(
host='localhost'))
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()複製程式碼我們想把warning和error的log記錄到一個檔案中：
$ python receive_logs_direct.py warning error > logs_from_rabbit.log複製程式碼列印所有log到螢幕：
$ python receive_logs_direct.py info warning error
[*] Waiting for logs. To exit press CTRL+C複製程式碼參考資料：
1. http://www.rabbitmq.com/tutorials/tutorial-four-python.html
2. http://blog.csdn.net/anzhsoft/article/details/19630147
