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Re: Test race condition? (unit test?)

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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.

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

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Test race condition? (unit test?) Simon <bad@example.com> - 2011-10-10 10:16 +0200
  Re: Test race condition? (unit test?) Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-10 08:36 -0400
    Re: Test race condition? (unit test?) Simon <bad@example.com> - 2011-10-10 15:48 +0200
      Re: Test race condition? (unit test?) The Natural Philosopher <tnp@invalid.invalid> - 2011-10-10 15:43 +0100
      Re: Test race condition? (unit test?) Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-10 13:42 -0400

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