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Provide automatic keepalive for certain groups, and session timeout notifications for everyone else.
Everyone knows how frustrating it is to be logged in, working on something important, only to learn that your session expired while you were working and all of your changes were lost. Session Keeper resolves that issue by allowing an administrator to specify which groups are to be kept alive automatically. Unlike other extensions that perform strange tests to figure out who is an admin, use wacky keepalive methods, or require you to enter a comma separated list of group ID numbers, this plugin allows an administrator to select from a multi-select list - exactly which groups are to be kept alive - and uses Joomla standard methods of keeping sessions active.
You might ask "But what about everyone else?"
An additional option of the plugin, is a notification message (JS confirm or Modal window with a countdown timer) that can appear at a configurable amount of time before the session expires - allowing the user to renew their session (without a page refresh). The user can also opt to dismiss the message (by cancelling or ignoring it) and their session will time out normally. When the session times out - the user will receive another notification that the session has timed out.
If you have the login module assigned to display on all pages, your logged in users will never see the warning message. This is because the Joomla login module enables keepalive for all pages where it appears. When keepalive is enabled on a page - the warning messages will not be displayed because the user will never time out. Either put the login module on specific pages only - or disable the warnings in this plugin.
Consider installing the RicheyWeb KeepaliveLight extension to benefit from the reduced resource use of KeepaliveLight vs the standard Keepalive mechanism built into Joomla.
With the option to use your own scripts, you no longer need to rely on Bootstrap to display a modal - you can trigger your own. While this may be beyond some users, I have created a non-Boostrap modal warning and expire notice that is ready to run now. Just unzip it somewhere in your Joomla media folder and use my HeadTag plugin to add it as a script for the "Registered" access level. Download the Reference Script - skreference.zip