| Re: Test race condition? (unit test?) [message #175588 is a reply to message #175583] |
Mon, 10 October 2011 12:36   |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma:
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Senior Member |
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On 10/10/2011 4:16 AM, Simon wrote:
> Hi,
>
> I have written a very simple file based lock/unlock system.
> the way it works is as follows.
>
> process A looks for File 'X', if file 'X' does not exists it tries to
> creates an empty file, 'Xa', and locks it, it then creates file 'X' and
> deletes file 'Xa'.
>
> process B is also looking for File 'X', if file 'X' does not exists it
> tries to create 'Xa', on failure it waits for a seconds and tries to
> obtain the lock again. Once/if the lock is obtained, it looks for file
> 'X' again and either uses it or creates it.
>
> process C looks for file 'X', if file 'X' exists it will use it.
>
> I try to write as much unit tests as possible and, as this is an
> important process, I would like to test the process above.
>
> 1- Can you think of any way I could test the above? As far as I know you
> cannot start multiple threads in php, (even in a dev environment).
>
> 2- Is there a better way of getting a lock like I am doing above?
>
> Many thanks
>
> Simon
Race conditions are always difficult to duplicate and troubleshoot when
they occur. And although with some third party tools you could process
php scripts in different threads, you probably don't want to (locking
between threads is different than locking between processes). The way
to typically troubleshoot such problems is to run multiple copies of the
script/program with waits for input at critical places. Run the script
concurrently from multiple windows to emulate the system.
The real question here is - what is the problem you're trying to
resolve. Without knowing that, it's difficult to recommend if there is
a better way.
--
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
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