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Building Scaleable Middleware for MMORPGs
CowboyRobot writes "ACM Queue has an article exploring the challenges of developing a reliable platform for an MMORPG, specifically looking at Wish by Mutable Realms. From the article: 'A common scalability problem for distributed multiplayer games relates to managing distributed sets of objects... A player may not be a member of more than one guild, or a guild may have at most one level-5 mage (magician). In computing terms, implementing such behavior boils down to performing membership tests on sets of distributed objects.'"
I really think computing power is less significant than the overall game development design when it comes to MMORPGs. After design, bandwidth becomes a factor, and only then is computing power a factor. The only exception I can think of would be requiring power for encryption/decryption.
The notion of parsing datasets for something like guild membership is really trivial. If you want to design a solid MMORPG, it's going to come down to how the world, objects and players are represented.
I continue to be in awe of the capabilities of games like Everquest and SWG. SOE has really created a very robust MMORPG technology -- it's hard for any other game developer to really say they have anything comparable when they can't demonstrate superior performance under the same conditions due to no other MMORPG having anywhere near the quantity of simultaneous players (as Everquest).
IMO, the client side of EQ is pretty straightforward. What makes the game special is the server side and how they manage to manipulate so many players and objects in real time. People complain that too many objects/players per "zone" can lag things down, and that is true, but I have yet to see a better implementation than Everquest. SWG has done away with the concept of "zones" to some degree, but basically, they seem to have implemented some client-side intelligence to indicate at which point additional graphics and information on objects in the distance should be loaded or reported. There are still "zones" in all these games. Some of them implement noticeable loading lags, and others don't.
My outside impression of the technical layout of Everquest is something like this... and I'd love anyone with more info/insight to correct me or elaborate further. I ASSume their system is made up of racks of servers, running Solaris I think. The have some low-level, propietary engine that manages the objects in the world, probably to a back-end database like Oracle. The reason for zones in EQ is that when you enter a new zone, you may actually be switching from one physical server to another. Not only do they have different servers for different shards/worlds, but different servers for different zones. When I see a system message such as, "North Karana, Velketors and Plane of Mischief going down for a brief update", I think that perhaps that's one server they're rebooting, which runs those particular zones. I suspect they stagger high-traffic zones with low-traffic zones on servers, and occasionally when the X number of zones managed by a single server have an unusually high amount of traffic/visitors, you get lag.
What's interesting about MMORPG game design is the balance between handling as much client-side as possible without creating security issues. If the server keeps track of players, NPCs and objects, it's much more difficult for someone to hack, or at least, logs are available to identify issues. The more client-side processing done, the more likely the game can be inappropriately manipulated.
When you take into account the amount of real-time data that goes back and forth, EQ (and SWG) are quite impressive. I don't think database/dataset issues are really the problem as being able to efficiently encapsulate, protect and send/receive the large amounts of data in the real-time world.
You can find a PDF version of the full article (exactly as printed in the magazine) here.
Cheers,
Michi.