[Xerte-dev] Re: Lockfiles

[Julian Tenney]

Didn't we get some improvements by making some assumptions to what 'stale' means, by looking at times / dates and comparing them to now.

So if lockfile made yesterday, probably not valid;
Etc

I'm way out of my comfort zone with this stuff, but do you get a session id, can you check to see if the creating session is still active when a new session attempts to open the file?

Is there a lockfile?
Which session made it?
Is that session still alive?

-----Original Message-----
From: xerte-dev-bounces at lists.nottingham.ac.uk [mailto:xerte-dev-bounces at lists.nottingham.ac.uk] On Behalf Of Pat Lockley
Sent: 29 February 2012 09:58
To: For Xerte technical developers
Subject: [Xerte-dev] Re: Lockfiles

That's the issue. I have a lock system already, and it suffers because they become stale.

On 29 Feb 2012, at 00:53, David Goodwin <david at palepurple.co.uk> wrote:

> Oh, it also looks like you need to explicitly call flock($fp, LOCK_UN) afterwards.
> 
> The alternative is, I guess, having a field in the DB to store who is currently editing a file - presumably storing a session_id in a field.
> The only problem with that is it would be possible on either a slow/busy/whatever webserver for two processes to think they had a "write" lock when in fact only one does, and you'd need some way of removing/detecting stale locks - so an LO isn't marked as being edited forever.
> 
> David
> 
> 
> On 29 Feb 2012, at 00:34, David Goodwin wrote:
> 
>> 
>> On 28 Feb 2012, at 23:50, Pat Lockley wrote:
>> 
>>> Stop concurrent access
>>> 
>> 
>> $fp = fopen('/path/to/something.xml.lock', 'w');
>> if(flock($fp, LOCK_EX, FALSE)) {
>>    // we have an exclusive lock on someting.xml.lock; within the scope of this webserver.
>> }
>> else {
>>   // someone else has access.
>> }
>> 
>> See also http://php.net/flock  - note it's behaviour is slightly different on Windows, and it wouldn't scale past more than one web server.
>> 
>> 
>> David.
>> 
>>> On 28 Feb 2012, at 23:45, David Goodwin <david at palepurple.co.uk> wrote:
>>> 
>>>> What do you mean by "lock an XML file down"
>>>> 
>>>> Are you trying to stop concurrent access to it, or something else?
>>>> 
>>>> David.
>>>> 
>>>> On 28 Feb 2012, at 22:26, Pat Lockley wrote:
>>>> 
>>>>> Hi all,
>>>>> 
>>>>> Thoughts on how to lock an XML file down?
>>>>> 
>>>>> I think it might be the session expiring, or the js might not fire properly. I am pretty sure the lockfile remove code doesn't use the session anymore.
>>>>> 
>>>>> 
>>>>> 
>>>> 
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>>>> 
>>>> 
>>>> 
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>> 'Business Web Application Development and Training in PHP'
>> 
>> http://www.palepurple.co.uk   
>> Office: 0845 0046746     Mobile: 07792380669 
>> 
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> 
> Pale Purple Ltd.  (Company No: 5580814)
> 'Business Web Application Development and Training in PHP'
> 
> http://www.palepurple.co.uk   
> Office: 0845 0046746     Mobile: 07792380669 
> 
> Follow us on Twitter: @PalePurpleLtd
> 
> 
> 
> 
> 
> 
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