Whenever the server is booted, there are a few tasks it runs right at the
beginning, before accepting connections or getting the value of
#0.dump_interval to schedule the first checkpoint (see below for more
information on checkpoint scheduling).
First, the server calls
$user_disconnected() once for each user who
was connected at the time the database file was written; this allows for any
cleaning up that's usually done when users disconnect (e.g., moving their
player objects back to some `home' location, etc.).
Next, it checks for the existence of the verb
there is such a verb, then the server runs a task invoking that verb with no
arguments and with
player equal to
#-1. This is useful for
carefully scheduling checkpoints and for re-initializing any state that is not
properly represented in the database file (e.g., re-opening certain outbound
network connections, clearing out certain tables, etc.).