Merge pull request #845 from balena-io/fix-download-race

Fix a race condition that could cause an unnecessary restart

src/application-manager.coffee

@@ -906,15 +906,19 @@ module.exports = class ApplicationManager extends EventEmitter
 			return Promise.reject(new Error("Invalid action #{step.action}"))
 		@actionExecutors[step.action](step, { force, skipLock })
 
-	getRequiredSteps: (currentState, targetState, ignoreImages = false) =>
+	getExtraStateForComparison: =>
 		@config.get('localMode').then (localMode) =>
-			Promise.join(
-				@images.isCleanupNeeded()
-				@images.getAvailable(localMode)
-				@images.getDownloadingImageIds()
-				@networks.supervisorNetworkReady()
-				@config.get('delta')
-				(cleanupNeeded, availableImages, downloading, supervisorNetworkReady, delta) =>
+			Promise.props({
+				cleanupNeeded: @images.isCleanupNeeded()
+				availableImages: @images.getAvailable(localMode)
+				downloading: @images.getDownloadingImageIds()
+				supervisorNetworkReady: @networks.supervisorNetworkReady()
+				delta: @config.get('delta')
+				localMode
+			})
+
+	getRequiredSteps: (currentState, targetState, extraState, ignoreImages = false) =>
+		{ cleanupNeeded, availableImages, downloading, supervisorNetworkReady, delta, localMode } = extraState
 		conf = _.mapValues({ delta, localMode }, (v) -> checkTruthy(v))
 		if conf.localMode
 			cleanupNeeded = false
@@ -925,7 +929,6 @@ module.exports = class ApplicationManager extends EventEmitter
 			@proxyvisor.getRequiredSteps(availableImages, downloading, currentState, targetState, nextSteps)
 			.then (proxyvisorSteps) ->
 				return nextSteps.concat(proxyvisorSteps)
-			)
 
 	serviceNameFromId: (serviceId) =>
 		@getTargetApps().then (apps) ->

src/device-state.coffee

@@ -584,17 +584,19 @@ module.exports = class DeviceState extends EventEmitter
 				@applyBlocker
 		.then =>
 			@usingInferStepsLock =>
-				Promise.join(
+				@applications.getExtraStateForComparison()
+				.then (extraState) =>
+					Promise.all([
 						@getCurrentForComparison()
 						@getTarget({ initial, intermediate })
-					(currentState, targetState) =>
+					])
+					.then ([ currentState, targetState ]) =>
 						@deviceConfig.getRequiredSteps(currentState, targetState)
 						.then (deviceConfigSteps) =>
 							if !_.isEmpty(deviceConfigSteps)
 								return deviceConfigSteps
 							else
-								@applications.getRequiredSteps(currentState, targetState, intermediate)
-				)
+								@applications.getRequiredSteps(currentState, targetState, extraState, intermediate)
 		.then (steps) =>
 			if _.isEmpty(steps)
 				@emitAsync('apply-target-state-end', null)