Add newTargetState event and use it for backup loading

Change-type: patch
Signed-off-by: Cameron Diver <cameron@balena.io>

src/api-binder.ts

@@ -8,8 +8,6 @@ import { PinejsClientRequest, StatusError } from 'pinejs-client-request';
 import * as url from 'url';
 import * as deviceRegister from './lib/register-device';
 
-import * as globalEventBus from './event-bus';
-
 import Config, { ConfigType } from './config';
 import Database from './db';
 import { EventTracker } from './event-tracker';
@@ -30,6 +28,7 @@ import { DeviceStatus, TargetState } from './types/state';
 import log from './lib/supervisor-console';
 
 import DeviceState from './device-state';
+import * as globalEventBus from './event-bus';
 import Logger from './logger';
 
 // The exponential backoff starts at 15s
@@ -207,11 +206,16 @@ export class APIBinder {
 		log.debug('Starting current state report');
 		await this.startCurrentStateReport();
 
-		await loadBackupFromMigration(
-			this.deviceState,
-			await this.getTargetState(),
-			bootstrapRetryDelay,
-		);
+		// When we've provisioned, try to load the backup. We
+		// must wait for the provisioning because we need a
+		// target state on which to apply the backup
+		globalEventBus.getInstance().once('targetStateChanged', async state => {
+			await loadBackupFromMigration(
+				this.deviceState,
+				state,
+				bootstrapRetryDelay,
+			);
+		});
 
 		this.readyForUpdates = true;
 		log.debug('Starting target state poll');

src/device-state.ts

@@ -17,6 +17,7 @@ import {
 	CompositionStepAction,
 } from './compose/composition-steps';
 import { loadTargetFromFile } from './device-state/preload';
+import * as globalEventBus from './event-bus';
 import * as hostConfig from './host-config';
 import constants = require('./lib/constants');
 import { InternalInconsistencyError, UpdatesLockedError } from './lib/errors';
@@ -447,6 +448,9 @@ export class DeviceState extends (EventEmitter as new () => DeviceStateEventEmit
 		this.failedUpdates = 0;
 
 		validateState(target);
+
+		globalEventBus.getInstance().emit('targetStateChanged', target);
+
 		const apiEndpoint = await this.config.get('apiEndpoint');
 
 		await this.usingWriteLockTarget(async () => {

src/event-bus.ts

@@ -1,9 +1,11 @@
 import { EventEmitter } from 'events';
 import * as _ from 'lodash';
 import StrictEventEmitter from 'strict-event-emitter-types';
+import { TargetState } from './types/state';
 
 export interface GlobalEvents {
 	deviceProvisioned: void;
+	targetStateChanged: TargetState;
 }
 
 type GlobalEventEmitter = StrictEventEmitter<EventEmitter, GlobalEvents>;