Share the code for fetching an image.

src/application.coffee

@@ -4,14 +4,15 @@ url = require 'url'
 knex = require './db'
 path = require 'path'
 config = require './config'
-{docker} = require './docker-utils'
+dockerUtils = require './docker-utils'
 PUBNUB = require 'pubnub'
 Promise = require 'bluebird'
-JSONStream = require 'JSONStream'
 PlatformAPI = require 'resin-platform-api/request'
 utils = require './utils'
 tty = require './tty'
 
+{docker} = dockerUtils
+
 PLATFORM_ENDPOINT = url.resolve(config.apiEndpoint, '/ewa/')
 resinAPI = new PlatformAPI(PLATFORM_ENDPOINT)
 
@@ -98,18 +99,7 @@ exports.start = start = (app) ->
 				utils.mixpanelTrack('Application install', app)
 				logSystemEvent('Installing application ' + app.imageId)
 				updateDeviceInfo(status: 'Downloading')
-				docker.createImageAsync(fromImage: app.imageId)
-				.then (stream) ->
-					return new Promise (resolve, reject) ->
-						if stream.headers['content-type'] is 'application/json'
-							stream.pipe(JSONStream.parse('error'))
-							.pipe(es.mapSync(reject))
-						else
-							stream.pipe es.wait (error, text) ->
-								if error
-									reject(text)
-
-						stream.on('end', resolve)
+				dockerUtils.fetchImage(app.imageId)
 			.then ->
 				console.log('Creating container:', app.imageId)
 				updateDeviceInfo(status: 'Starting')

src/docker-utils.coffee

@@ -1,6 +1,8 @@
 Docker = require 'dockerode'
 Promise = require 'bluebird'
 config = require './config'
+JSONStream = require 'JSONStream'
+es = require 'event-stream'
 
 docker = Promise.promisifyAll(new Docker(socketPath: config.dockerSocket))
 # Hack dockerode to promisify internal classes' prototypes
@@ -8,3 +10,16 @@ Promise.promisifyAll(docker.getImage().__proto__)
 Promise.promisifyAll(docker.getContainer().__proto__)
 
 exports.docker = docker
+exports.fetchImage = (image) ->
+	docker.createImageAsync(fromImage: image)
+	.then (stream) ->
+		return new Promise (resolve, reject) ->
+			if stream.headers['content-type'] is 'application/json'
+				stream.pipe(JSONStream.parse('error'))
+				.pipe(es.mapSync(reject))
+			else
+				stream.pipe es.wait (error, text) ->
+					if error
+						reject(text)
+
+			stream.on('end', resolve)

src/supervisor-update.coffee

@@ -1,10 +1,12 @@
 config = require './config'
-{docker} = require './docker-utils'
+dockerUtils = require './docker-utils'
 Promise = require 'bluebird'
 _ = require 'lodash'
 es = require 'event-stream'
 fs = Promise.promisifyAll(require('fs'))
 
+{docker} = dockerUtils
+
 localImage = config.localImage
 remoteImage = config.remoteImage
 
@@ -93,7 +95,6 @@ currentConfigPromise = currentContainerPromise.then (container) ->
 # This is a promise that resolves when we have fully initialised.
 exports.initialised = currentConfigPromise.then (currentSupervisor) ->
 	utils = require './utils'
-	JSONStream = require 'JSONStream'
 
 	supervisorUpdating = Promise.resolve()
 	exports.update = ->
@@ -102,18 +103,7 @@ exports.initialised = currentConfigPromise.then (currentSupervisor) ->
 		supervisorUpdating = supervisorUpdating.then ->
 			utils.mixpanelTrack('Supervisor update check')
 			console.log('Fetching supervisor:', remoteImage)
-			docker.createImageAsync(fromImage: remoteImage)
-		.then (stream) ->
-			return new Promise (resolve, reject) ->
-				if stream.headers['content-type'] is 'application/json'
-					stream.pipe(JSONStream.parse('error'))
-					.pipe(es.mapSync(reject))
-				else
-					stream.pipe es.wait (error, text) ->
-						if error
-							reject(text)
-
-				stream.on('end', resolve)
+			dockerUtils.fetchImage(remoteImage)
 		.then ->
 			console.log('Inspecting new supervisor:', remoteImage)
 			docker.getImage(remoteImage).inspectAsync()