Moodle in English: Weird message in php error log file

Weird message in php error log file

by Mari Cruz García - Thursday, November 27, 2014, 8:41 PM

Hello,

I wonder if anybody could shred some light regarding the following problem:

A month ago I upgraded our Moodle production site to Moodle 2.6.5 which is a very solid a reliable version. Our site runs on a Windows Server 2008-IIS7 virtual machine. We use php 5.5.13 and I have configured opcache in php.ini by the book following the instructions in Moodle.org

https://docs.moodle.org/26/en/OPcache

The day before yesterday, I installed some Windows security updates in the virtual machine and I restarted windows. The free space in the hard disk that runs Windows is 45 GB and the used space is 55 GB. I reported this to the network technical but the free space is not a problem, apparently, and 45 GB is enough for keep running IIS7.

Yesterday, after the installation of the updates and after I restarted Windows, we started to experience very weird problems: Moodle did not upload the css elements with the frontpage (that is: the frontpage was uploaded without the css of our theme), the site was specially slow and if you click in a course or resource, the screen went black (although there were not error entries in the php error log file).

I looked at the entries in the php error log file for yesterday and this is what I found:

_______________________________________________________________________________________________________________________

[26-Nov-2014 19:10:49 Asia/Kuwait] Cannot obtain session lock for sid: pdgev7ood0n3egu82sgh1u4m62

[26-Nov-2014 19:12:38 Asia/Kuwait] Cannot obtain session lock for sid: pdgev7ood0n3egu82sgh1u4m62

[26-Nov-2014 19:12:47 Asia/Kuwait] Cannot obtain session lock for sid: pdgev7ood0n3egu82sgh1u4m62

[26-Nov-2014 19:13:06 Asia/Kuwait] Cannot obtain session lock for sid: pdgev7ood0n3egu82sgh1u4m62

_______________________________________________________________________________________________________________________

19:00 Kuwait time (where our server is hosted) corresponds to 4:00 UK time, when I restarted IIS logging into the Windows machine.

Restarting IIS seem to have sorted the problem so far, but I am very concerned that it may happen again.

Does anybody know what do the 'Cannot obtain session lock for sid:....' messages mean and this is a seriour error or not?

Thank you very much for your advice.

Mari Cruz

Re: Weird message in php error log file

by Jordi Pujol-Ahulló - Sunday, November 30, 2014, 5:52 PM

Hi,

Probably the state of the server after updating remained inconsistent in some way.

The kind of messages makes me think about session management based on files. And probably some kind of permissions was temporary denied or inconsistent due to the updating.

In my opinion, and according to my experience, keep an eye on that and if repeated, make a deep search in such a situation to find out what really happens.

Best,

Jordi

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Re: Weird message in php error log file

by Howard Miller - Monday, December 1, 2014, 7:15 PM

Where are you storing sessions? If using the database then don't!

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Re: Weird message in php error log file

by Mari Cruz García - Thursday, December 4, 2014, 11:58 PM

Thank you very much for reply.

How can I find out if I am storing sessions in the database, Howard?

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Re: Weird message in php error log file

by Mari Cruz García - Friday, December 5, 2014, 12:24 AM

I have found the information:

https://learning.health.org.kw/admin/settings.php?section=sessionhandling

I also found the following information in Moodle.org:

https://docs.moodle.org/26/en/Session_handling

However, I am confused about how to configure correctly config.php according to that page. We don't use a memcached server so my understanding is that the memcached configuration options in config.php are not applicable.

Are the options of 'Files' and 'Database' applicable:

$CFG->session_handler_class = '\core\session\file';
$CFG->session_file_save_path = $CFG->dataroot.'/sessions';

$CFG->session_handler_class = '\core\session\database';
$CFG->session_database_acquire_lock_timeout = 120;

The information says that the database driver was used for Moodle 2.0-2.5 installations, but not for Moodle 2.6

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Weird message in php error log file