The Importance of Session IDs

The Session Clustering (SC) process starts when a user’s browser sends a request to a web server. The Web Server then sends a request to the Session Server, which in turn checks if with the request there is, a cookie, specifically one containing a Session ID. If a Session ID is found, the web server can find the server by session and resume the previous session. If a Session ID is not found, the web server creates a new Session ID and sends a cookie containing the new Session ID to the browser.

Session Key Format

When a session is saved without Session Clustering (modfied php extension), you will see in the logs only in the Session Key.

The Session Key format is: Master-Port-Backup-Port-Version-Key. The backup port is only used for High Availability therefore, when HA is not in use, the session key will be: Master-Port-00000000-00000000-Version-Key.

HA Note:

The format Master-Port-00000000-00000000-Version-Key will also appear in HA mode if you are working on a cluster with only one available server or when evaluating the product with only one server.

To obtain SC functionality the SC module changes the Session ID’s standard format as follows:

1. Internal information is stored in the Session ID.

2. Session IDs are stored by the Session Cluster module and therefore do not resemble Session IDs created by other PHP session modules (e.g. mod_files).

As a result of these dependencies and changes, other modules should not use Session Clustering's Session IDs.

Important Note:

When deploying SC in an organization it is forbidden to change the Session ID for any reason and in any way (such as using the PHP function session_id() ).