-
Notifications
You must be signed in to change notification settings - Fork 0
Introduction to servers in lordofpomelo
The server-side of lordofpomelo is a distributed server cluster, including serveral scenes servers, one or more pathfinding servers, chat server , gate server, global server, long connected servers, etc..
![Backend server] (http://pomelo.netease.com/resource/documentImage/lordofpomelo/backend.png)
Unlike the short web connection used in web server, in lordofpomelo, all connections between clients and servers are persistence connections. server network game connection. These connections require a certain amount of resources to keep alive. In lordofpomelo, we use websocket protocal to establish persistent connection between html5 game clients and the node.js game servers, the connections servers are used to maintain these connections, and transit message between clients and servers. The connection state is maintained by the form of player session, which is used to the user's login status, user's basic information, as well as the user's websocket connection information .
Gate server is the entrance for websocket clients. For there area always connectors, and a player will never know which one to connect. To solve this problem. gate server provide a fixed websocket port for all players : to establish a connector to lordofpomelo, first the client will connect to gate server, pass the auth verification and get a connector address provide by servers. Then the client will cut off the connect with gate server, and connect to a connectoion server.
Authentication server is responsible for user registration and authentication. It is the unified entrance of user authentication, and provide RPC interface for other servers. It is used to hide the details of authentication, and provide a uniform authentication interface.
In online game, a game world will divide into serveral areas, in consideration of the performance and load balance. In lordofpomelo, a game map is corresponding to a game scene, and sever by a single area server,. A game scene can not be divided, and also can not be simplely parallel extended. Therefore, the scene is the basic unit of the game world in lordofpomelo. A area server is responsible for maintaining all the entities, and integration of related services.
The the scene server handles almost all logic in the game interface to manipulate scene data, as well as other service providers. While the scene itself can not be divided in the lordofpomelo, but by adding new scenes to increase the capacity of the game scene services can also be run independently for horizontal expansion.
Pathfinding service is one of the basic services of a game server, it is the foundation of many player's basic action: moving, chazing and so on.Pathfinding is used to find the shortest path between two points in a game map. It is a typical stateless, compute-intensive calculations, in the lordofpomelo, we separate the pathfinding logic from scene logic, thereby reducing the load of the scene server. Becase the service is stateless,pathfinding server can be easily parallel extensions, you just need to add more servers, and they are all the same. The pathfinding use A* algorithm based on a metric of collisions, provides a general computing interface, and packaged as a independent module(see link).
The chat service is one of the basic services of the online games.In lordofpomelo, chat service is separation from scene logic, and powered by a separate chat server. Chat server maintains all the online player's information, and use these data to communicate with connector servers, to support the communication between players.
The lordofpomelo scene services area used to manage all the entities in the scene and the game world. For security and consistency, all the game logic are running or verifing at server side, and these game logic are running at the area server. So, the scence server is the core server of lordofpomelo, and the most complex server. in the following part, we will analysis on the area server in lordofpomelo:
In lordofpomelo, each game scene corresponding to a separate area server, all the business logics in a scene are implement in the server. Cross-scene operations are supportted by a global server. The following picture is the functionality inside an area server:
![Area] (http://pomelo.netease.com/resource/documentImage/lordofpomelo/area.png)
All entities in the game will be loaded into memory when enter the game scene, then all the modifications on these entities will be directly operate in memory, and usedata synchronization module ynchronize these changes to the database timingly. This design makes all the data manipulation in game scene into direct memory operations, improving overall performance by avoiding the solw IO operations.
All the definitions of entities in lordofpomelo are in the entity folder of domain directory, using object-oriented design philosophy.All the objects in the scene are inherited from the entity object. The adding and removing operation of entities are implement by a unified interface of area, thereby reducing the cost of objects management.
The message service in lordofpomelo can be divided into two different types: one-to-one RPC request-response, and one-to-many broadcast messages. Because the logic verification in lordofpomelo is running at service side, most of the client's requests need a response from server, these replies use request/response mode like web server.
In lordofpomelo, we use AOI based notification service. i.e: when the server side produce a broadcast message, we will use the aoi service to get a list of players need to notified, and then broadcast messge the list instead of all the players in the area, thereby greatly reducing the number of messages.
In a game, player's view is often far less than the size of the scene, the scene of most of the message, a simple scene broadcast is not necessary and can not afford. When news occurs, and how to determine the need to notify the object of the message is the AOI module.
The lordofpomelo achieve AOI service is based on the lighthouse, the basic way the entire map is divided into large tower, each tower service maintains a list of objects, object point in this tower range. Then, at the basis of this data structure up to trigger various AOI event.