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Bug #37319 "MySQL server has gone away", with PDO::ATTR_PERSISTENT => true
Submitted: 2006-05-05 02:40 UTC Modified: 2006-12-12 01:00 UTC
Votes:15
Avg. Score:4.3 ± 0.8
Reproduced:14 of 14 (100.0%)
Same Version:2 (14.3%)
Same OS:1 (7.1%)
From: j8859 at clix dot pt Assigned: wez (profile)
Status: No Feedback Package: PDO related
PHP Version: 5.1.3 OS: Linux Slackware 10.2
Private report: No CVE-ID: None
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 [2006-05-05 02:40 UTC] j8859 at clix dot pt 
Description:
------------
This error also occurs with PHP 5.1.2, but with more frequency than with 5.1.3.

It occurs only if I use PDO::ATTR_PERSISTENT => true, and it never occurs with PDO::ATTR_PERSISTENT => false.

I have several databases in MySQL, several programs in PHP some using the classic MySQL functions, others using MySQLi, and one using PDO. This is the one which produces errors.

The MySQL version is 5.0.18. Apache/1.3.34.

If I do a MySQL Flush Tables, the error stops.
With PHP 5.1.2 I also need to do an Apache restart to get the error stop occurring.

The error never occurred with few MySQL tables opened.
I do a diary crontab backup with mysqldump, over the night, and in the morning there are about 220 opened tables.
Then, when I use my PDO application, I start getting "MySQL server has gone away" errors.

I changed to PDO::ATTR_PERSISTENT => false and the error never happened.
I changed back to PDO::ATTR_PERSISTENT => true and the error returned.

I know this can be difficult for you to reproduce it, because it is not a deterministic error, but I'm sure there is an error.

Reproduce code:
---------------
$bd = new PDO();
$query = "SELECT * FROM mytable";
$inst = $this->prepare($query);
if(!$inst) die ("ERROR: " . $query . ", " . __FILE__ . ", " .  __LINE__);
if(!$inst->execute()) { $inst->closeCursor(); return; }
while($reg = $inst->fetch(PDO::FETCH_ASSOC)) {
	// Process $reg
}
$inst->closeCursor();
$bd = null;

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 [2006-05-06 09:52 UTC] j8859 at clix dot pt 
It occurs also with PHP 5.1.4.
 [2006-05-24 22:27 UTC] wez@php.net 
Try following the tips here:
http://netevil.org/node.php?uuid=444a6017-0548-2459-2943-44a601714d58
 [2006-05-26 13:41 UTC] j8859 at clix dot pt 
Apparently the problem stopped occurring.
I'll see what happens in the next days.
Anyway, the solution you suggest 
-- $db->setAttribute(PDO::ATTR_EMULATE_PREPARES, true); --
is it a temporary or a definitive one?
 [2006-05-28 10:59 UTC] j8859 at clix dot pt 
After applying your suggestion, the problem didn't occur again.
Anyway, I guess this should only be a temporary solution, isn't it?
 [2006-12-04 15:12 UTC] iliaa@php.net 
Please try using this CVS snapshot:

  http://snaps.php.net/php5.2-latest.tar.gz
 
For Windows:
 
  http://snaps.php.net/win32/php5.2-win32-latest.zip
 [2006-12-12 01:00 UTC] php-bugs at lists dot php dot net 
No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".
 [2008-09-03 20:12 UTC] arsukdeo at technocorp dot com 
Sep 03, 2008:

This problem might not be specific to a given version of linux, but with respect to the nature of the web server handles processes with PDO.
 
I have a client running:  php 5.1.6 on centos (Linux -.-.- 2.6.18-92.1.6.el5 i686)with apache 2.0 and the "MySQL server has gone away" problem still occurs.

Interestingly, I developed a core framework with the necessary db "access code" using PDO on XP with IIS and I did not see a problem until I tried to run the code on centos.  The access code uses ATTR_PERSISTENT set to true.

At the moment, I haven't found the triggering mechanism.  The client's server was standalone and there was no load on it.

In any case, this is a real problem that requires investigation and it should be fixed ASAP.
 [2009-01-22 14:46 UTC] bsr at gmail dot com 
Can also add that I have the problem on Centos 5.2. For me, the problem exists whether persistent is set to true or false.
 
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