I don't get it.
If the consumer and the producer are separate threads, why does the consumer thread block when the producer thread is generating a new board? Or why does it take forever for the producer thread to be pre-empted?
Also, I don't understand why the solution works. How does sleeping for .001 seconds right after putting a new board on the queue solve the problem?
Evan Simpson wrote:
WEBoggle needs a new game board every three minutes. Boards take an unpredictable (much less than 3min, but non-trivial) amount of time to generate. The system is driven by web requests, and I don't want the request that happens to trigger the need for the new board to have to pay the time cost of generating it.
I set up a producer thread that does nothing but generate boards and put them into a length-two Queue (blocking). At the rate that boards are pulled from the Queue, it's almost always full, but my poor consumer thread was still being blocked for "a long time" each time it fetched a board.
At this point I realized that q.get() on a full Queue immediately wakes up the producer, which has been blocked waiting to add a board to the Queue. It sets about generating the next board, and the consumer doesn't get to run again until the producer blocks again or is preempted.
The solution was simple: have the producer time.sleep(0.001) when q.put(board) returns.
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