producer and consumer how to exit gracefully?

Question

my task is improving efficiency of making rpc call. I believe I can use producer and consumer example. producer will get response, whereas consumer will write the received object to file.

I write a sample program for producer & consumer problem. It looks good. However, my question is that how does consumer know when to exit ?

here is my code:

  5 is_exit = False
  6 product = []
  7
  8 def consumer(cond):
  9     global product
 10     global is_exit
 11
 12     while True:
 13         cond.acquire()
 14         while len(product) == 0:
 15             cond.wait()
 16         product = product[1:]
 17         print 'consume one product'
 18         cond.release()
 19
 20 def producer(cond):
 21     global product
 22     global is_exit
 23
 24     for i in range(10):
 25         cond.acquire()
 26         print 'produce one good'
 27         product.append(199)
 28         cond.notify()
 29         cond.release()
  /// I use .join() to wait all threads to finish.

since producer will only produce 10 goods, there must be some way to notify consumer that producer will not produce anything and you should exit.

any advises will be helpful. Thanks a lot.

PS. what I mean 'gracefully' is that I want to consumer will not do any extra work as soon as producer tells him that there is no more goods to be produced.

score 3 · Accepted Answer · answered Feb 21 '13 at 20:24

The producer can send a special "poison pill" object down the queue, as a signal that no more data is coming and that the consumer should shut down. Obviously, the consumer will have to know about the poison pill (make it a global constant thing) and look out for it, and handle it correctly.

This is a common pattern for dealing with this kind of scenario.

producer and consumer how to exit gracefully?

1 Answers1