System variables blocks.
This is a very old and almost vestigial part of Megistos. It was modeled
after the corresponding part of the Major BBS. However, Megistos' design
was very different from the design that imposed the system variable block
on the Major BBS. As a result, this part of the system really shows its
age. It should be removed at some point, for a very large number of
reasons:
- Stability: even given the unbelievably paranoid backup policy of the
system variable file, this is the most common point-of-failure for the
BBS. It has numerous natural enemies, including stupidity, race conditions,
disk crashes, et cetera.
- It's a binary structure (and file) and that always spells disaster
for maintenance and recovery.
- Most of the fields no longer make sense. For that matter, many of the
fields found in Major's system variable block weren't really applicable
when I started programming the Major BBS in 1992. Having room for a single
voice phone is stupid, if your BBS has 32 lines and a telnet
connection. Having by-the-minute charges is silly, if you have monthly
subscriptions. Having charges is silly if you run a free system.
- All of the fields here should be present because there is absolutely
no other place to put them. This clearly does not hold for most
fields. Even the statistics block could easily be moved to the
data/stats directory where all the other statistics are. BBS names,
addresses, et cetera are handled by substitution variables. No need to
involve global state for things that are seldom needed.
- The system variable block was meant to service a centralised system,
where everything was a single process, with a single view of
memory. Megistos is pretty distributed. The BBS is split among different
processes, with global state (such as it is) being kept by the BBS daemon
(bbsd).
Given all that, I'm not going to document the entire structure.
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