Queue enhancement suggestion

Hendrik van Rooyen mail at microcorp.co.za
Tue Apr 17 07:23:35 CEST 2007


"Antoon Pardon" <a..n at forel.vub.ac.be> wrote:


> The problem is this doesn't work well if you have multiple producers.
> One producer can be finished while the other is still putting values
> on the queue.
>
> The solution I have been thinking on is the following.
>
> Add an open and close operation. Only threads that have the queue
> open can access it. The open call should specify whether you
> want to read or write to the queue or both. When all writers
> have closed the queue and the queue is empty a q.get will
> raise an exception. This may be done by putting a sentinel
> on the queue when the last writer closed the queue.
>

This is beginning to look like a named pipe to me.

The nice thing about queues is that there is currently so little
BS about them - you just import the module, create one by binding
a name to it, and you are in business, and anyone can read and/or
write to it.

If I were faced with the sort of thing addressed by this thread, I would
probably use some sort of time out to decide when the end has happened.
After all - if the task is long running, it never stops (hopefully), and if its
a batch type job, it runs out of input and stops putting stuff on the queue.

It means you have to use non blocking gets and try - except, though.
But then - to use any of the methods put forward in this thread,
you have to use try - except anyway...

Why does this remind me of COBOL:

read input_file at end go to close_down  ?

: - )

- Hendrik







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