Session synchronization in WorldServer
There are two types of user sessions in WorldServer: a back-end session (the WorldServer legacy session) and a UI session (managed by Spring). The two sessions are synchronized through calls to the REST API and the session.synchronization.rate property in the ui.properties file determines when those calls are made.
For example, let's assume that you set both the back-end session and the UI session to 600 seconds. If it is not absolute, the back-end session can be extended by 600 seconds when a user performs an action. The UI session, however, uses a different logic, hence the need to synchronize the two sessions. If session.synchronization.rate=4, then a call is made to the REST API when there are 600/4=150 seconds left of the initial UI session, to see if the back-end session has been extended and to synchronize the UI session with it. If the response is that the back-end session has been extended, then the UI session is extended as well, but only after a call. If a UI session has expired, but the back-end session hasn't expired, the login page is displayed and the user will still have to log in again.
The default value of the session.synchronization.rate property is 4 and you can specify values between 1 and 5. If you specify a value lower than 1 or higher than 5, the default minimum (1) or default maximum (5) value will be used instead.