So I'm working on a node.js game server application at the moment, and I've hit a bit of a wall here. My issue is that I'm using socket.io to accept inbound connections from game clients. These clients might be connected to one of several Zones or areas of the game world.
The basic architecture is displayed below. The master process forks a child process for each Zone of the game which runs the Zone Manager process; a process dedicated to maintaining the Zone data (3d models, positions of players/entities, etc). The master process then forks multiple "Communication Threads" for each Zone Manager it creates. These threads create an instance of socket.io and listen on the port for that Zone (multiple threads listening on a single port). These threads will handle the majority of the game logic in their own process as well as communicate with the database backing the game server. The only issue is that in some circumstances they may need to communicate with the Zone Manager to receive information about the Zone, players, etc.
As an example: A player wants to buy/sell/trade with a non-player character (NPC) in the Zone. The Zone Communication thread needs to ask the Zone Manager thread if the player is close enough to the NPC to make the trade before it allows the trade to take place.
The issue I'm running into here is that I was planning to make use of the node.js cluster functionality and use the send() and on() methods of the processes to handle passing messages back and forth. That would be fine except for one caveat I've run into with it. Since all child processes spun off with cluster.fork() can only communicate with the "master" process. The node.js root process becomes a bottleneck for all communication. I ran some benchmarks on my system using a script that literally just bounced a message back and forth using the cluster's Int