Question

I have a queue which can contain max 4 queued objects. These objects are threads running web service requests. The thread part is OK.
I have followed many tutorials which talk about consumer and producer threads used to fill in and out the queue object.
My question is about the consumer part. In all these tutorials and regarding the python doc, the only way I have found to pile out objects from the queue is :

while len(requltArray) < amountOfThreads:
    thread = q.get(True)
    thread.join()

Imagine the q.get(True) piles out a thread with an invalid web service request. And imagine this thread have to wait for urllib timeout to end. My consumer will be blocked for some seconds. As my queue is limited to 4 threads and maybe the 3 others have ended yet, I waste time until consumer can continue the pile-outs (and producer can fill the queue).

Is there any way or well-known design pattern to avoid this waste of time ?

Thanks for your help

Answer 1

Maybe you could use conditions

Imagine you want to put a new thread into your queue but it is full. Then you could wait() for the condition object (pseudo code):

condition.acquire()
while not queue.has_free_place():
    condition.wait()
add_new_thread_to_queue()
condition.release()

And inside your queued threads you could place something like the following code at the end of execution:

condition.acquire()
remove_myself_from_queue()
condition.notify()
condition.release()