使用消息队列的线程同步不是为了

Question

以下代码是从Raymond's Pycon keynotes on cuncurrency，很棒的演示。这是一个有点长，所以我会用这个问题开始：

• 如果消息加到一起到队列，以前被认为是一个线程中完成的，怎么来的，他们都应该打印打印烂漫？在线程初始化之间添加一个100ms的延迟解决了这个问题，输出和预期的一样。

-

import Queue, time 

counter_queue = Queue.Queue() 
counter = 0 

def counter_manager(): 
    # I have EXCLUSIVE rights to update the counter variable 
    global counter 

    while True: 
     increment = counter_queue.get() 
     counter += 1 
     print_queue.put(['The count is {}\n'.format(counter), 
         '----------\n']) 
     counter_queue.task_done() 

t = threading.Thread(target=counter_manager) 
t.daemon = True 
t.start() 
del t 


print_queue = Queue.Queue() 

def print_manager(): 
    # I have EXCLUSIVE rights to call the print keyword 
    while True: 
     job = print_queue.get() 
     for line in job: 
      print line 
     print_queue.task_done() 

t = threading.Thread(target=print_manager) 
t.daemon = True 
t.start() 
del t 

def worker_threads(): 
    counter_queue.put(1) 

print_queue.put(['Starting up.. with message queues']) 
worker_threads = [] 
for i in range(10): 
    t = threading.Thread(target=worker) 
    worker_threads.append(t) 
    t.start() 
    # time.sleep(0.1) 
for t in worker_threads: 
    t.join() 

counter_queue.join() 
print_queue.put(['Finishing up']) 
print_queue.join() 

它使用counter_manager和print_queue作为后台从工作线程接收消息，并且顺序地执行它们。据我所知，这应该保持执行的顺序。但是，我得到以下输出：

Starting up.. with message queues 
The couns is 1The couns is 2 

-------------------- 

The couns is 3 
----------The couns is 4 
The couns is 5 
The couns is 6 
---------- 
---------- 
---------- 
The couns is 7 

----------The couns is 8 

The couns is 9---------- 

----------The couns is 10 

---------- 
Finishing up 

计数器正确递增，仍然打印消息被打乱。

如果我取消睡眠声明，线程初始化是由100ms的延迟，输出正确

Starting up.. with message queues 
The couns is 1 
---------- 
The couns is 2 
---------- 
The couns is 3 
---------- 
The couns is 4 
---------- 
The couns is 5 
---------- 
The couns is 6 
---------- 
The couns is 7 
---------- 
The couns is 8 
---------- 
The couns is 9 
---------- 
The couns is 10 
---------- 
Finishing up 

使用队列，版画应该是为了。这不正确吗？

---

工人代码

def worker(): 
    global counter 

    counter += 1 
    print 'The couns is {}'.format(counter) # read the var (race cond.) 
    print '----------' 

Answer 1

我无法复制的问题。为了让它运行，我添加了一个threading导入并将worker_threads函数重命名为worker。

输出有“couns”，但代码显示“count”。你可以验证你提供的输出和代码是否一致？

您的输出似乎只在行级交错。

我不知道以前版本的代码在counter_manager中有两个不同的.put（不是原子的），后来被合并为一个具有多行的.put？