From: [EMAIL PROTECTED]
Operating system: Linux
PHP version: 4.0.6
PHP Bug Type: Unknown/Other Function
Bug description: Session (concurrency ?) problem
While testing a php apllication, I found that I had some trouble with
session variables (php4 native sessions, not phplib's crappy ones), at this
point I was using a custom MySQL session handler (with
session_set_save_handler).
After adding some error_log calls in my custom session handler functions, I
managed to see that the problem was coming from the fact that a session
was reopened before the current one was written to the database :
(in chronological order)
request A request B
HTTP request A is made on page1.php
session open by session_start:
session variable A equals 0
request A is being treated:
session variable A is set to 1
redirection is made with header()
to page2.php ------------------> request B is made on
page2.phpA
exit()
session open by session _start
session variable A equals 0
treatment made by my
application:
no change to make to
variable A if
variable A is 0
php saves the session
=> A is stored with value 1 exit()
php saves the session
=> A is stored with value 0
And in the end, A ends up being 0, which is not what it should be.
I found a way of making the bug go away (for a moment) : make a sleep(2) in
my session 'open' handler. :)))
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.
Then I thought that such a locking should have been done by the php session
layer itself, because this issue is common to all session handlers you can
use or define. And I found in the online documentation session_end and
session_readonly which seemingly were tackling with similar concurrency
issue, and I concluded this was worked on and would probably be solved in
some next release, but php 4.0.6 doesn't solve the problem, and the
session_end and session_readonly functions - though they appear in the
documentation - are not even appearing in the CVS code.
So my question : is this really a known issue ? is a fix for this planned
soon ?
Thank you !!
--
Edit bug report at: http://bugs.php.net/?id=12267&edit=1
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