python实现简单的redis 队列 SIMPLE PYTHON QUEUE WITH REDIS

lang110

The following article shows how to useredisto build a simple multi-producer, multi-consumer Queue with an interface similar to thepython
standardlib queue. With this queue you can easily share data between multiple processes or offload time consumig calculations to multiple worker processes.

To store the data we use theredis list data type. Redis Lists stores simple strings sorted by insertion order.

The following redis commands are used:

• 
  rpushInsert an element at the tail of the list
  
• 
  blpopGet an element from the head of the list, block if list is empty
  
• 
  lpopGet an element from the head of the list, return nothing list is empty
  
• 
  llenReturn the length of the list
  

The implementation uses theredis-pylibrary to talk to the server.



import redis
class RedisQueue(object):
"""Simple Queue with Redis Backend"""
def __init__(self, name, namespace='queue', **redis_kwargs):
"""The default connection parameters are: host='localhost', port=6379, db=0"""
self.__db= redis.Redis(**redis_kwargs)
self.key = '%s:%s' %(namespace, name)
def qsize(self):
"""Return the approximate size of the queue."""
return self.__db.llen(self.key)
def empty(self):
"""Return True if the queue is empty, False otherwise."""
return self.qsize() == 0
def put(self, item):
"""Put item into the queue."""
self.__db.rpush(self.key, item)
def get(self, block=True, timeout=None):
"""Remove and return an item from the queue.
If optional args block is true and timeout is None (the default), block
if necessary until an item is available."""
if block:
item = self.__db.blpop(self.key, timeout=timeout)
else:
item = self.__db.lpop(self.key)
if item:
item = item[1]
return item
def get_nowait(self):
"""Equivalent to get(False)."""
return self.get(False)


使用方法：



>>> from RedisQueue import RedisQueue
>>> q = RedisQueue('test')
>>> q.put('hello world')

Now if we have a look at the redis database with theredis-cliclient
it shows the expected results:



redis 127.0.0.1:6379> keys *
1) "queue:test"
redis 127.0.0.1:6379> type queue:test
list
redis 127.0.0.1:6379> llen queue:test
(integer) 1
redis 127.0.0.1:6379> lrange queue:test 0 1
1) "hello world"

We can get the item from a different script with:



>>> from RedisQueue import RedisQueue
>>> q = RedisQueue('test')
>>> q.get()
'hello world'


A subsequent call ofq.get()will block until anotherone puts a new item into the Queue.

The next step would be to an endoder/decoder (e.gpython-json) to the Queue so that you are not limited to send strings.

There alredy exists the nice and simplehotqueuelibrary which has the same interface as the above example and provides encoding/decoding.

Other mentionable queue implementations with a redis backend are:

• 
  flask-redisA basic Message Queue with Redis for flask.
  
• 
  celeryAn asynchronous task queue/job queue based on distributed message passing. Much more advanced. Can be used with different storage backends.
  
• 
  rqSimple python library for queueing jobs and processing them in the background with workers.
  
• 
  resqueis a Redis-backed Ruby library for creating background jobs, placing them on multiple queues, and processing them later. Used at github. Includes a nice monitoring
  web interface.
  
• 
  pyresA resque clone in python.
  

FRom：http://peter-hoffmann.com/2012/python-simple-queue-redis-queue.html