Drupal 7 sessions wiped after changing settings.php Yesterday afternoon I had an administrator uncomment and modify the $base_url variable in our production environment. Any changes made in the repository fires off a redeployment which has never been an issue. Upon the server coming back up, we started receiving complaints that user's who were now logged out.

Does changing settings.php do something behind the scenes that I'm unaware about (session.cookie_lifetime or session.gc_max_life).

I do not have access to the database nor can I retrieve it from our prod environment. 

Any help is appreciated so that we don't run into this issue again!
This is likely due to the value changing, which changes the way they are recorded:

https://api.drupal.org/api/drupal/includes!bootstrap.inc/function/drupal_settings_initialize/7.x

$base_url and $cookie_domain - changing these values in settings.php will affect any user who was authenticated before if the values change, and will need to re-authenticate.