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Communication Layer
This document describes the communication layer in Clusterio and unless you're developing Clusterio it's probably not going to be very useful for you.
Communication is facilitated by the lib/link library and is based on three core abstractions: links, connectors and messages. Links represents one side of a two way communication pipe, connectors deal with connecting and establishing communication, and messages are the content sent over the link.
Link
The Link class represents one side of a two way communication channel where the actual communication is done by a connector associated with the link. The link also knows what the endpoint types it's connected to are via the source and target attributes.
The endpoint types currently implemented are controller, host, instance, and control. Although host and instances run in the same Node.js program they use virtual links to communicate between them in order to simplify the communication architecture.
Upon creation the link will register with the connector in order to receive and process messages from it. The messages received are validated using the validator registered for the type of the message. A message for which there is no validator for is considered an error.
Connector
The connector used with a link is responsible for establishing and/or maintain the connection that messages are sent over. Reconnect logic is expected to be implemented in the connector, though this has not yet been done.
There's also the virtual connector which lets two links in the same program be connected to each other without having to establish a network connection.
Message
There's two types of messages currently implemented apart from the Link builtin close message and that's Request and Event. The builtin messages are defined in packages/lib/src/link/messages.ts and are attached to links via the attachAllMessages function, which is usally called in the Link subclass constructor.
The messages define which links they are valid on and only attaches handlers for those links. There's also a forwarding mechanism for when a request or event is to be forwarded another hop.