[MUD-Dev] Server stability (was: Player statistics)

[Bruce]

"Koster, Raph" wrote:
> Bruce wrote:
> > Or the reverse ... are there people who feel that a server that
> > crashes once/week is fine, that the customers will still be happy
> > and life will go on, and so the invested effort (since time is
> > money) is overkill and doesn't pay off from a business perspective?
> > Maybe server stability really doesn't matter that much, so long as
> > data isn't lost often and the players can be kept happy.
> 
> The goal is always to get to 100% uptime and the servers just aren't
> there, but it's also true that these services make a habit of bringing
> down the servers frequently (weekly or more) anyway to do things like
> add content, do patches, etc. So there's a valid "why bother?"
> argument to be made, as long as the uptime exceeds the periodic
> downtime schedule.

This is interesting.

Having to restart a server just to add new content or install
bugfixes seems to a movement in opposition to the text-based MUD
community.  From my perspective, the move within the text-based
community has been towards less downtime and systems that can be
modified or have content changes done at runtime.

Am I leading -that- sheltered an existence by being used to make
almost any sort of change without needing to restart my server?

> Now, if it doesn't, customers get very unhappy. Especially in the case
> of something like UO, which like a MOO/MUSH, saves full world state
> for *everything* in the game. That comes out at (last I recall) 17
> million objects per server, or in real time terms, a 3 hour boot time
> to read it off of disk. :)

Ouch.  Sounds like your DB guys looked at MOO or something. :)

Cold hasn't got this 'problem', as it is a disk-based system, and
demand load objects from the on-disk database.  At startup, we
need only to read in the object index to build a bitmap
describing the real database's layout (which is used to know
where the free space in the binary file is).  The bitmap is a
design decision which is used in place of keeping track of the
free spaces with a free list. (There is some research being done
to determine whether a free list might perform better in some
circumstances.)

On The Etenal City, our database of objects is around 1.3 gigs,
while the object index is around the index is 192M.  We could
further optimize our startup costs by saving the bitmap to disk
and loading that.  I'm not terribly inclined to do that though
because we don't crash or restart often enough for this to be a
worry. :)

(Thanks go out to Brad, one of my fellow occasional Cold
developers (and MUD-Dev lurker) for working through this topic
with me in discussions.)

 - Bruce
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