ImlightActor Fundamentals
Overview
Imlight is built on the Actor Model, a model that defines single units of computation called "actors."
An actor is an isolated, stateful component that:
- Process messages one at a time from its mailbox
- Maintains its own private state
- Can create child actors
- Communicates only through messages in lieu of calling methods/functions
Actor System
The Actor System is the top-level container for all actors in Imlight. It manages the lifecycle of actors, including their creation, supervision, and termination. Actors cannot exist on their own: they must be part of an Actor System, and as a child of another actor.
Actor Supervisors
Since actors are isolated and do not share state, they can fail independently. To handle failures gracefully, Imlight employs a supervision strategy where parent actors (supervisors) monitor their child actors. If a child actor fails, the supervisor can decide to restart it, stop it, or escalate the failure.
Actor Hierarchy in Imlight
Imlight consists of three main server types:
- Login Server: Handles user authentication, character selection, and initial connection to game servers.
- Game Server: Manages game worlds, zones, player interactions, NPCs, and game logic.
- Patch Server: Serves game patches and updates to clients.
INFO
The login server is the supervisor of all game servers. When a game server starts, it registers itself with the login server to make itself available for client connections.
The three server types define the same basic actor hierarchy:
- TcpListenerActor: Listens for incoming TCP connections.
- MessageServices: Handle specific functionalities (e.g., authentication, character management, quests).
- SocketListener and SocketSender: Manage low-level socket communication.
Hierarchy Diagram
For the sake of clarity, the aforementioned actors are not shown in the hierarchy below, but they exist in each server type.
Message Handling
In vanilla Akka.NET, actors communicate by sending and receiving untyped messages. Imlight extends this concept by implementing a strongly-typed message handling system that supports custom protocols and dispatchers.
Please review the Message Handling documentation for more details.
Session Actors
When a new client connects to a server, a Session Actor is created to manage the connection.