Yii memcache session got invalidated after deployment

Question

Every time I deploy my Yii app, I change the symbolic link of the /var/www. Something similar like this

rm -f /var/www
ln -s /var/app-version /var/www

But every time I do this, the user sessions got invalidated (i.e. all of the users got logged out and CSRF tokens were reset).

For the session I use CCacheHttpSession. Something like below in the main.php

'components' => [
    'memcache' => [
        'class' => 'CMemCache',
        'servers' => [
            [
                'host' => 'localhost',
                'port' => 11211,
            ]
        ]
    ],
    'user' => [
        'class' => 'WebUser',
        'allowAutoLogin' => true,
    ],
    'session' => [
        'class' => 'CCacheHttpSession',
        'cacheID' => 'memcache'
    ]
]

I'm not sure whether this misconfiguration is in PHP-level or Yii-level, but what did I do wrong?

Answer 1

By default CCache will use a keyPrefix that contains Yii::app()->id. This unique ID is calculated as a hash of the current basePath plus the name of the application. If you look at setBasePath() you see, that it will use the realpath(). This causes symlinks to be resolved to their origin.

So if the origin of your symlink changes, this will lead to a different application ID, which again leads to a changed cache key prefix. And this invalidates your cache content.

To fix this, you can either

• Set a static id on the application in your main.php configuration, or
• Set a static keyPrefix on your memcache component.

The latter is recommended anyway, if you have more than one server that all should access the same memcached pool.