500 Response: "Unable to clear session lock record" during checkout when using Memcached for sessions

Red Hat Enterprise Linux Server release 6.8 (Santiago)
php-common-7.0.8-1.el6.remi.x86_64
php-pecl-memcached-3.0.0-0.1.20160217git6ace07d.el6.remi.7.0.x86_64
memcached-1.4.27-1.el6.remi.x86_64

Steps to reproduce using PHP 7.0.8 with Memcached 1.4.27 for Session Storage on RHEL 6.8 x64

1. Install Magento from 2.0, 2.1 and develop CE branch.
2. Ensure PHP Memcached Session Lock Wait Minimum is default value of 0

php -i|grep sess_lock_wait_min

memcached.sess_lock_wait_min = 0;
3. Add Configurable Product to the cart.
4. Attempt to complete checkout

Expected result

1. Checkout completes without any error responses from server.

Actual result

1. Occasionally, Error occurs: "500 Response" During AJAX Checkout Steps, No UI feedback.
2. Error is logged in var/report/$(date +%s)
   
   a:4:{i:0;s:187:"Warning: SessionHandler::read(): Unable to clear session lock record in /var/www/magento2/demo_example_com/lib/internal/Magento/Framework/Session/SaveHandler/Native.php on line 22";i:1;s:6232:"#0 [internal function]: Magento\Framework\App\ErrorHandler->handler(2, 'SessionHandler:...', '/var/www/magent...', 22, Array)

Possible Workaround

1. Edit /etc/php.d/50-memcached.ini
   
   - memcached.sess_lock_wait_min = 0;

+ memcached.sess_lock_wait_min = 250;
2. Restart PHP-FPM

As this setting was not identified as required in the following documents, I am curious if 250 milliseconds is a good value and if it may impact any other areas of functionality.
http://devdocs.magento.com/guides/v2.1/install-gde/system-requirements.html
http://devdocs.magento.com/guides/v2.0/install-gde/system-requirements.html

[martiGIT]

same issue at Magento 2.1 with memcached 1.4.21-1.1 at debian 8. Also changing memcached.sess_lock_wait_min to 250
memcached.sess_lock_wait_min = 250
does not resolve this issue.

a:4:{i:0;s:167:"Warning: SessionHandler::read(): Unable to clear session lock record in (...)/magento/framework/Session/SaveHandler/Native.php on line 22";i:1;s:5977:"#0 [internal function]: Magento\Framework\App\ErrorHandler->handler(2, 'SessionHandler:...', '(...)/publi...', 22, Array)

[hendywijaya]

Hi Guys,
I found the similar issue with Magento EE 1.14 setup
PHP 7.0.9
php-pecl-memcached-3.0.0-0.1.20160217git6ace07d.el6.remi.7.0.x86_64
libmemcached-0.31-1.1.el6.x86_64
memcached-1.4.25-1.el6.remi.x86_64

In Magento 1.14, this issue prevents the user to even login to the site, I managed to get this working by setting memcached.sess_locking = Off which is far from ideal, since this would be catastrophic during race / concurrent condition (trust me I've been there watching my quote session went haywire).

This may not be Magento 2 specific issue, but more of PHP7 + memcached session storage

[hendywijaya]

Hi Guys,

a bit of update, this happens on
php-pecl-memcached-3.0.0-0.1.20160217git6ace07d.el7.remi.7.0.x86_64

but not on
php-pecl-memcached-2.2.0-3.el6.remi.5.6.x86_64

so it's seems issue is related to pecl itself, haven't been able to replicate the issue using non-magento php script, but if you are to, you can report the issue to : https://github.com/php-memcached-dev/php-memcached

[tim-reynolds]

I wanted to add that I have a client on EE 2.1 and downgrading to the previous version of the module worked for us, as recommended by @hendywijaya

[peec]

Same issue here. Using memcached cluster client from AWS (memcached 2.1.0).

This error happens occasionally, and is very important to fix. The error can happen in both frontend and backend.

• Magento: 2.1.1
• Amazon linux ( EC2 )
• Nginx
• PHP 7 & php-fpm
• Memcached: https://github.com/awslabs/aws-elasticache-cluster-client-memcached-for-php ( which is in fact based on memcached 2.1.0 - https://github.com/php-memcached-dev/php-memcached. )

One of the methods that last caused this error:

1. Add a new configurable product
2. Add some data to the product, including some simple products in the configurable.
3. Try to save the product.
4. After a bit of waiting for the request to finish.. 500 error and "Unable to clear session lock record" in the log files.

Our temporary fix:

Use database for sessions, ugh..

[joates-ldg]

I'm running the same setup as @peec but with 2.1.3 and experiencing the same issue.

However I can login to the admin, we are instead receiving an error on the product overview page of the admin while trying to load an ajax page.

I've switched to DB for sessions, which has resolved the issue, however again I don't think this is a long term fix.

We had a recurrence of this issue with a client and, as @hendywijaya recommended, were unable to find a packaged 2.2.0 branch of PHP-Pecl-Memcached for PHP7 (without compiling). In order to resolve this issue we decided to implement Redis for session storage using the Magento 2 docs. The issue has not recurred since switching session storage to Redis. We will monitor this for a few days an post an update, but we believe we are simply avoiding memcache to avoid this issue.

needless to say, this has not recurred

[elyobo]

Probably caused by php-memcached-dev/php-memcached#266; workaround is to explicitly set memcached.sess_lock_expire (with the same value as max_execution_time being a sane default).

[ewbarnard]

We see the problem while upgrading Magento EE 1.14.0.1 using PHP 7.2 and the latest pecl memcached extension. Has "unable to clear session lock record" been solved? I've tried tweaking various php ini settings as described elsewhere to no avail.