Is this the right architecture for our MMORPG mobile game?_问答_开发者

These days I am trying to design architecture of a new MMORPG mobile game for my company. This game is similar to Mafia Wars, iMobsters, or RISK. Basic idea is to prepare an army to battle your opponents (online users).

Although I have previously worked on multiple mobile apps but this is something new to me. After a lot of struggle, I have come up with an architecture which is illustrated with the help of a high-level flow diagram:

Is this the right architecture for our MMORPG mobile game?

We have decided to go with client-server model. There will be a centralized database on server. Each client will have its own local database which will remain in sync with server. This database acts as a cache for storing things that do not change frequently e.g. maps, products, inventory etc.

With this model in place, I am not sure how to tackle following issues:

What would be the best way of synchronizing server and client databases?
Should an event get saved to local DB before updating it to server? What if app terminates for some reason before saving changes to centralized DB?
Will simple HTTP requests serve the purpose of synchronization?
How to know which users are currently logged in? (One way could be to have client keep on sending a request to server after every x minutes to notify that it is active. Otherwise consider a client inactive).
Are client side validations enough? If not, how to revert an action if server does not validate something?

I am not sure if this is an efficient solution and how it will scale. I would really appreciate if people who have already worked on such apps can share their experiences which might help me to come up with something better. Thanks in advance.

Additional Info:

Client-side is implemented in C++ game engine called marmalade. This is a cross platform game engine which means you can run your app on all major mobile OS. We certainly can achieve threading and which is also illustrated in my flow diagram. I am planning to use MySQL for server and SQLite for client.

This is not a turn based game so there is not much interaction with other players. Server will provide a list of online players and you can battle them by clicking battle button and after some animation, result will be announced.

For database synchronization I have two solutions in mind:

Store timestamp for each record. Also keep track of when local DB was last updated. When synchronizing, only select those rows that have a greater timestamp and send to local DB. Keep a isDeleted flag for deleted rows so every deletion simply behaves as an update. But I have serious doubts about performance as for every sync request we would have to scan the complete DB and look for updated rows.
Another technique might be to keep a log of each insertion or update that takes place against a user. When the client app asks for sync, go to this table and find out which rows of which table have been updated or inserted. Once these rows are successfully transferred to client remove this log. But then I think of what happens if a user uses ano开发者_如何学运维ther device. According to logs table all updates have been transferred for that user but actually that was done on another device. So we might have to keep track of device also. Implementing this technique is more time consuming but not sure if it out performs the first one.

I've actually worked on some of the titles you mentioned. I do not recommend using mysql, it doesn't scale up correctly, even if you shard. If you do you are loosing any benefits you might have in using a relational database. You are probably better off using a no-sql database. Its is faster to develop, easy to scale and it is simple to change the document structure which is a given for a game. If your game data is simple you might want to try couchDB, if you need advanced querying you are probably better of with MongoDB. Take care of security at the start. They will try to hack the game for sure and if you have a number of clients released it is hard to make security changes backward compatible. SSL won't do much as the end user is the problem not an eavesdropper. Signing or encrypting your data will make it harder for a user to add items and gold to their accounts. You should also define your architecture to support multiple clients without having a bunch of ifs and case statements. Read the client version and dispatch that client to the appropriate codebase. Have a maintenance mode with flags for upgrading, maintenance, etc. It will cut you some slack if you need to re-shard your DB or any other change that might require downtime. Client side validations are not enough, specially if using in app purchases. I agree with the above post. Server should control game logic. As for DB sync, its best to memcache read only data. Typical examples are buyable items, maps, news, etc. User data is harder as you might not be able to afford loosing any modified data. The easiest setup is to cache user data for a couple of hours and write directly to the DB every time. If you are using no-sql it will probably withstand a high load without the need of using a persistence queue.

I see two potential problem hidden in the fact that you store all the state on the client, and then update the state on the server using a background thread.

How can the server validate the data being posted? If someone hacked your application, they could modify the code so whenever they swing their sword (or whatever they do in your game), it is always a hit. Doing that in a single player game is not that big a deal, but doing that in an MMORPG can ruin the experience for everyone else. So the server should validate every update of data - or even better, the server should be in charge of every business rule. So when you swing your sword against an opponent, that should be a server call, and the server returns whether or not it is a hit, and how many hit points the opponent lost.
What about interaction with other players (since you say it is an MMORP, there will be interaction with other players)? Since you say that you update the server, and get updates in a background thread, interaction will be sluggish. When you communicate with another character you have first wait for you background thread to sync data, but you also have to wait on the background thread of the other player to sync data.

Looks nice. But what is the client-side made of ? Web ? Can you use threading to synchronize both DB ? I should make the game in that way that it interacts immediately with the local DB, and let some background mechanism do the sync (something like a snapshot). This leads me to think about mysql replication. I think it is worth to be tried, but I never did. It also brings you answers to other questions. But what about the charge (how many customers are connected together) ?

http://dev.mysql.com/doc/refman/5.0/en/replication.html

Make your client issue commands to the server ("hit player"), and server send (relevant) events to client ("player was killed"). I wouldn't advice going with data synchronization. Server should be responsible for all important game decisions.