Bug #12267 Updated: Session (concurrency ?) problem
ID: 12267
Updated by: kalowsky
Reported By: thomas.morin@webmotion.com
Old Status: Open
Status: Bogus
Bug Type: Session related
Operating System: Linux
PHP Version: 4.0.6
New Comment:
marked as bogus according to Sascha Schumanns email pasted below:
Subject:
Re: [PHP-DEV] Bug #12267 Updated: Session (concurrency ?) problem
Date:
Fri, 20 Jul 2001 21:22:39 +0200 (MEST)
From:
Sascha Schumann <sascha@schumann.cx>
To:
<thomas.morin@webmotion.com>
CC:
<php-dev@lists.php.net>
This should not be a bug report. Please respond by email.
Previous Comments:
------------------------------------------------------------------------
[2001-07-20 11:15:36] thomas.morin@webmotion.com
I would tend to think that :
- make the file session handler race safe- make the mm session handler race safe
- make the a MySQL session handler race safe
- make the a PostgreSQL session handler race safe
- make whatever other session handlers race safe
- ...
...can become code functionnality duplication. No ?
Solving the problem for all handlers by locking the session at a higher level would appear to me as
the most reliable and elegant solution. But I have to admit I don't know the internals of php
to know if it is possible or not.
I'm really surprised, because when I saw the session_end and session_readonly documentation, I
thought that proper locking was made (or at least would be made at some point) in sessions, but your
are explaining to me that this is not the case... so I have to admit I don't really understand
what I should do...
Quote from http://www.ca.php.net/manual/en/function.session-end.php
:
<< [...]as session data is locked to prevent concurrent writes only one script may operate on
a session at any time >>
- For the mm handler, is a fix planned ?
- Is there a session handler which would be race safe (files ?) ?
------------------------------------------------------------------------
[2001-07-20 08:31:31] kalowsky@php.net
Comments from Sascha Schumann on the php-dev list:
> The fact is a similar problem is happening with the mm module,
> but here I can't insert error_log to be sure... is this session
> handler "race safe" ?
Nope.
> And I'm surprised that this concurrency issue has to be solved
> on a per handler basis : isn't it functionnality duplication ?
> isn't this a tricky trap for handler programmers ? is this
> mentionned in the documentation ?
Locking a record in your database is not duplication of
functionality.
------------------------------------------------------------------------
[2001-07-20 08:30:33] kalowsky@php.net
Comments on the php-dev list, by Sascha Schumann:
> This "solved" the problem and I concluded the bug was only due to my fault
> : I should have locked my session table (or row...) to avoid race
> conditions and concurrency problems.
That is right. The session storage handlers have to perform
locking themselves, if they are supposed to be suited for
concurrent accesses.
------------------------------------------------------------------------
[2001-07-19 16:57:40] thomas.morin@webmotion.com
The fact is a similar problem is happening with the mm module, but here I can't insert
error_log to be sure... is this session handler "race safe" ?
And I'm surprised that this concurrency issue has to be solved on a per handler basis :
isn't it functionnality duplication ? isn't this a tricky trap for handler programmers ?
is this mentionned in the documentation ?
------------------------------------------------------------------------
[2001-07-19 15:49:12] thomas.morin@webmotion.com
Sorry for the layout, my 2 columns are broken.
I also changed the 'Type' of the bug to 'Session related'.
------------------------------------------------------------------------
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the rest of the comments, please view the bug report online at
http://bugs.php.net/?id=12267
Edit this bug report at http://bugs.php.net/?id=12267&edit=1
Thread (11 messages)