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PHP sessions not being saved in memcache

Posted by: admin July 12, 2020 Leave a comment

Questions:

Running an application using php 5.4 on AWS using the Amazon Linux.

PHP version is PHP 5.4.28.
memcache lib installed from the AWS repo is php54-pecl-memcache-3.0.8-1.11.amzn1.x86_64

I have verified that php is using /etc/php.ini:

[[email protected]]# php -i | grep Config
Configuration File (php.ini) Path => /etc
Loaded Configuration File => /etc/php.ini

The setting show that I should be using memcache:

[[email protected] etc]# grep "^session.save" php.ini
session.save_handler="memcache"
session.save_path="tcp://<elasticache-endpoint>:11211"

[[email protected] php.d]# php -i | grep session.save
session.save_handler => memcache => memcache
session.save_path => tcp://<elasicache-endpoint>:11211?persistent=1&weight=1&timeout=1&retry_interval=15 => tcp://<elasticache-endpoint>:11211?persistent=1&weight=1&timeout=1&retry_interval=15

I can telnet from the box to the end point & port and connect properly, so the instance is able to connect to the memcached server.

Things that we have tried:

  • I have removed the tcp:// from the php.ini file, and that made no difference – sessions are still getting saved in files.
  • We have changed from session.save_handler=”memcache” to session.save_handler=”memcached”
  • each time we make a change, we stop the httpd server, and then start it again
  • we have even tried rebooting the servers

Regardless of what we’ve tried, sessions are stored on disk to /var/lib/php/sessions.
Is there something I’m missing, or is this a known 5.4 or AWS issue?

How to&Answers:

OK, we managed to figure out the issue.

First, we created a simple page that spit out phpinfo(). Note that it is important that you run this thru the web server – running php -i DOES NOT include any overrides that apache may add.

Under the session section, the output lists all the directives, and a “Local Value” and a “Master Value”.

The local values had:

session.save_handler    files
session.save_path   /var/lib/php/session

while the master values had:

session.save_handler    memcache
session.save_path   tcp://<endpoint>:11211

It turns out that there’s an override installed by default in /etc/httpd/conf.d/php.conf that specifies the files. This appears to be a Redhat/CentOS/Fedora thing.

Removing those values from php.conf fixed the problem.

Answer:

Both of the major memcache PHP PECL extensions have session handlers. Either will require you to install a PECL module before use.

The Memcache PECL extension session handler is enabled with the following in php.ini:

session.save_handler = "memcache"
session.save_path = "tcp://memcacheServerAddressHere:11211?persistent=1&weight=2&timeout=2&retry_interval=10"

The Memcached PECL extension session handler is enabled with the following in php.ini:

session.save_handler = "memcached"
session.save_path = "memcacheServerAddressHere:11211"

Note that the Memcache extension appears to allow more configuration of the Memcache environment.