cabal-state

Run a state machine inside a cabal-core channel

Status: Experimental

motivation

I wanted to create something less formal than a smart contract, but still does a shared vm and could be auditable.

Use cases could include:

• small group workflows. Lets take on docusign, voting, etc
• jackbox style p2p games with no host server. The shared game state runs over the cabal channel.
• more ideas to come...

usage

const Cabal = require('cabal-core')
const CabalState = require('cabal-state')
const RAM = require('random-access-memory')
const machineDfn = require('cabal-state-example-button')
const key = '0201400f1fa2e3076a3f17f4521b2cc41e258c446cdaa44742afe6e1b9fd5f82'
const cabal = Cabal(RAM, key)
const service = CabalState.fromJson(cabal, machineDfn, 'default')
service.onTransition(state => {
  console.log(state.value);
  console.log(state.context)
});
cabal.swarm(() => {})

API

const service = CabalState.fromJson(cabal, machineDfn, channel)

Create a running service, which is an instance of XState interpreter

• cabal is a cabal-core p2p database
• machineDfn json file that defines the state machine. It will run in a VM sandbox. See Creating the machineDfn
• channel channel name the state machine will listen for events to transition its current state.

Sandbox

Xstate allows for functions to execute as gaurd conditions, to compute state, and to have some side effects. Currently, we run all code in a vm2 sandbox, and only allow access to the console, and the things needed to mutate xstate context.

Its very important in a distributed environment that the state machine is side effect free. For example, adding fetch to the sandbox would cause many issues.

Creating The MachineDfn

The machine is defined in json, so it is portable. We have tools that help a developer write the machine in js and then build the json from that. The js is practically an Xstate machine with some limitations.

A machine is best published to npm (but does not have to be). This gives it a reasonable place to be versioned, publicly auditable, and easy to share. It the future we may build alternate repos for them. An example machine is the Example Button which will be reference below.

1. Create a folder for the machine
2. Create a xstate index.js machine. It is mostly xstate format, with the exception that all actions, assignments, and guards are reference by strings, and the function are objects with keys that match.
3. Run cabal-state index.js. This converts the js to a portable json format in the index.json file.
4. create a package.json file that exports the index.json file, eg "main": "index.json",
5. publish to npm