Comments on: MMO games are still screwed up in their database technology

By: Joe Hellerstein

Joe Hellerstein — Thu, 25 Jun 2009 00:53:38 +0000

ack.. here’s that link again to the Cornell Data-Driven Games project….

By: Joe Hellerstein

Joe Hellerstein — Thu, 25 Jun 2009 00:52:19 +0000

Have a look at some very interesting general trend toward declarative programming in research on achieving the next generation of scalable software.

By: Ben Werther

Ben Werther — Wed, 17 Jun 2009 02:25:03 +0000

This isn’t really DBMS related at all, but is kind of on topic–

There is a way to mostly escape the “choose 2 of the above” (in the previous comment).
When I was at There.com, Ken Duda (now VP of Eng at Arista) conceived of one of the most impressive pieces of technology I’ve ever come across – a massively scalable distributed physics simulation engine for MMOGs.

The servers would run the simulation and maintain the true state of the world (allowing high security). All clients would also simulate locally based on all the information they’d received. The challenge is how to hide latency so that everything moves smoothly but the user can control their avatar interactively without waiting for a round trip back from the server. The magic was a ‘relativistic’ model where objects further away from the user would run at the server’s clock, while anything closer to the user would shift into his local extrapolated timeframe. This means that everything runs smoothly without snapping, except in the case where two users’ actions interact at close quarters in a way that conflict (and so they snap when the server tells them what really happened).

With this model a user could play billiards in an MMOG with no local latency and fully correct collisions from the perspective of all observers. Only if two players hit balls within a few hundred milliseconds of each other would there be a chance for a momentary snap until each received each other’s event from the server. Amazing technology — and ahead of anything since as far as I’m aware.

http://www.google.com/patents?id=ZmUOAAAAEBAJ

By: Curt Monash

Curt Monash — Wed, 17 Jun 2009 02:03:57 +0000

That’s actually covered in one of my articles on Guild Wars, if you follow the links.

But classical DBMS transactions would seem to meet the test.

By: Pete Mancini

Pete Mancini — Wed, 17 Jun 2009 01:53:53 +0000

There is an additional dimension here that you are forgetting about. MMOs have to contend with active and malicious hackers. These dudes are active 24/7 trying to hack the game so they can win fights, have more loot, etc. A lot of rational technology fixes have to be thrown out completely because they open the door for the hackers to cause trouble. With in-game items selling for ACTUAL MONEY on sites like eBay there is plenty of motive for the hacker. The problem domain is pretty intense and beyond the normal $50/hr programmer or outsourced programming shop in Bongolesia. So highly lag free, highly secure and no data loss is one of those “choose 2 of the above” questions right now. If you can get the first two and make is so that important individual information is replicated locally that would give a means for getting the third item (albeit after the fact when the Server and Client do a sync after high traffic.) I am sure the software engineers at these MMO companies are as hard pressed to solve the problem as you are living it by playing the games.

By: Curt Monash

Curt Monash — Tue, 16 Jun 2009 17:22:13 +0000

There’s a thread on the LOTRO forums based on this post, but so far it’s generated more heat than light.

http://forums.lotro.com/showthread.php?t=273641

By: Curt Monash

Curt Monash — Tue, 16 Jun 2009 10:57:55 +0000

True, Dan, and up to a point “rubber-banding” is tolerated by players, if recent actions are lost.

LOTRO sometimes loses 15 minutes or more of play at a time. I never experienced more than half a minute or so of loss on Guild Wars.

Anyhow, I think the parts of LOTRO that are like OLTP transactions are sent out to different subsystems and perhaps different physical servers. And latency on them is often at the very annoying finger-tapping level.

By: Daniel Weinreb

Daniel Weinreb — Tue, 16 Jun 2009 10:16:21 +0000

But just moving a player from point A to point A + delta does not, and that’s what has the most stringent latency requirements.

By: Curt Monash

Curt Monash — Mon, 15 Jun 2009 13:17:14 +0000

Dan,

MMOs have what’s described as an “in-game economy”, with manufacturing and retail transactions resembling those of real life. Those need to be ACID for the same reasons they need to be ACID in the real world.

CAM

By: The database technology of Guild Wars | DBMS2 -- DataBase Management System Services

Mon, 15 Jun 2009 12:08:12 +0000

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