Moleculer-state-machine NPM

Moleculer State Machine

Moleculer State Machine is an add on for the Moleculer microservices framework that allows services to be extended with finite-state machine behavior. It does so by acting as a high level wrapper for javascript-state-machine.

Basic Usage

Moleculer State Machine will look in the service settings for the state machine options:

const StateMachine = require("moleculer-state-machine");

{
    name: "service-with-state-machine",
    mixins: [
        StateMachine
    ],
    settings: {
        initialState: "new",
        stateTransitions: [
            {name: "age", from: "new", to: "old"}
        ]
    }
}

In this example calling age() on the service will trigger a transition from "new" to "old".

Delegations

The mixin delegates the methods is, can, cannot, transitions, allTransitions, allStates, and the state property to an internal instance of javascript-state-machine that is created on service creation.

Events

The mixin emits all javascript-stage-machine events as service events prefixed by the service name. The onBeforeTransition event for example will emit on the broker test.onBeforeTransition. The event payload will be as follows:

{
    event: ..., // the name fo the event
    transition: ..., // the name of the transition function
    from: ... // the state being transitioned from
    to: ... // the state being transitioned to
}

See javascript-state-machine lifecylce events for more details.

Callbacks

Methods can be defined on the service that will be called when a specific state machine event occurs. These callbacks are called with the same arguments as as events.

See javascript-state-machine lifecylce events for more details.