lib/src/lifecycle/Unit.ts

import {AppClass} from './AppClass'

/**
 * The various statuses of a Unit.
 */
export enum UnitStatus {
    Starting,
    Started,
    Stopping,
    Stopped,
    Error,
}

/**
 * Base class for a service that can be registered with the application
 * that is started and stopped during the application lifecycle.
 */
export abstract class Unit extends AppClass {
    /** The current status of the unit. */
    public status: UnitStatus = UnitStatus.Stopped

    /**
     * This method is called to start the unit when the application is booting.
     * Here, you should do any setup required to get the package up and running.
     */
    public up(): Promise<void> | void {}  // eslint-disable-line @typescript-eslint/no-empty-function

    /**
     * This method is called to stop the unit when the application is shutting down.
     * Here, you should do any teardown required to stop the package cleanly.
     *
     * IN PARTICULAR take care to free blocking resources that could prevent the
     * process from exiting without a kill.
     */
    public down(): Promise<void> | void {}  // eslint-disable-line @typescript-eslint/no-empty-function
}