balena-cli/lib/utils/compose.coffee
Paulo Castro 7dd33adfd1 Fix 'balena build --emulated' on Windows (including default docker socket)
Change-type: patch
Signed-off-by: Paulo Castro <paulo@balena.io>
2019-10-09 13:10:49 +01:00

818 lines
24 KiB
CoffeeScript

###*
# @license
# Copyright 2017-2019 Balena Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
###
Promise = require('bluebird')
path = require('path')
exports.appendProjectOptions = appendProjectOptions = (opts) ->
opts.concat [
{
signature: 'projectName'
parameter: 'projectName'
description: 'Specify an alternate project name; default is the directory name'
alias: 'n'
},
]
exports.appendOptions = (opts) ->
appendProjectOptions(opts).concat [
{
signature: 'emulated'
description: 'Run an emulated build using Qemu'
boolean: true
alias: 'e'
},
{
signature: 'dockerfile'
parameter: 'Dockerfile'
description: 'Alternative Dockerfile name/path, relative to the source folder'
},
{
signature: 'logs'
description: 'Display full log output'
boolean: true
},
{
signature: 'registry-secrets'
alias: 'R'
parameter: 'secrets.yml|.json'
description: 'Path to a YAML or JSON file with passwords for a private Docker registry'
},
]
exports.generateOpts = (options) ->
fs = require('mz/fs')
fs.realpath(options.source || '.').then (projectPath) ->
projectName: options.projectName
projectPath: projectPath
inlineLogs: !!options.logs
dockerfilePath: options.dockerfile
compositionFileNames = [
'docker-compose.yml'
'docker-compose.yaml'
]
# look into the given directory for valid compose files and return
# the contents of the first one found.
exports.resolveProject = resolveProject = (rootDir) ->
fs = require('mz/fs')
Promise.any compositionFileNames.map (filename) ->
fs.readFile(path.join(rootDir, filename), 'utf-8')
# Parse the given composition and return a structure with info. Input is:
# - composePath: the *absolute* path to the directory containing the compose file
# - composeStr: the contents of the compose file, as a string
createProject = (composePath, composeStr, projectName = null) ->
yml = require('js-yaml')
compose = require('resin-compose-parse')
# both methods below may throw.
composition = yml.safeLoad(composeStr, schema: yml.FAILSAFE_SCHEMA)
composition = compose.normalize(composition)
projectName ?= path.basename(composePath)
descriptors = compose.parse(composition).map (descr) ->
# generate an image name based on the project and service names
# if one is not given and the service requires a build
if descr.image.context? and not descr.image.tag?
descr.image.tag = [ projectName, descr.serviceName ].join('_').toLowerCase()
return descr
return {
path: composePath,
name: projectName,
composition,
descriptors
}
# high-level function resolving a project and creating a composition out
# of it in one go. if image is given, it'll create a default project for
# that without looking for a project. falls back to creating a default
# project if none is found at the given projectPath.
exports.loadProject = (logger, projectPath, projectName, image, dockerfilePath) ->
{ validateSpecifiedDockerfile } = require('./compose_ts')
compose = require('resin-compose-parse')
logger.logDebug('Loading project...')
Promise.try ->
dockerfilePath = validateSpecifiedDockerfile(projectPath, dockerfilePath)
if image?
logger.logInfo("Creating default composition with image: #{image}")
return compose.defaultComposition(image)
logger.logDebug('Resolving project...')
resolveProject(projectPath)
.tap ->
if dockerfilePath
logger.logWarn("Ignoring alternative dockerfile \"#{dockerfilePath}\"\ because a docker-compose file exists")
else
logger.logInfo('Compose file detected')
.catch (e) ->
logger.logDebug("Failed to resolve project: #{e}")
logger.logInfo("Creating default composition with source: #{projectPath}")
return compose.defaultComposition(undefined, dockerfilePath)
.then (composeStr) ->
logger.logDebug('Creating project...')
createProject(projectPath, composeStr, projectName)
exports.tarDirectory = tarDirectory = (dir, preFinalizeCallback = null) ->
tar = require('tar-stream')
klaw = require('klaw')
path = require('path')
fs = require('mz/fs')
streamToPromise = require('stream-to-promise')
{ FileIgnorer } = require('./ignore')
{ toPosixPath } = require('resin-multibuild').PathUtils
getFiles = ->
streamToPromise(klaw(dir))
.filter((item) -> not item.stats.isDirectory())
.map((item) -> item.path)
ignore = new FileIgnorer(dir)
pack = tar.pack()
getFiles(dir)
.each (file) ->
type = ignore.getIgnoreFileType(path.relative(dir, file))
if type?
ignore.addIgnoreFile(file, type)
.filter(ignore.filter)
.map (file) ->
relPath = path.relative(path.resolve(dir), file)
Promise.join relPath, fs.stat(file), fs.readFile(file),
(filename, stats, data) ->
pack.entry({ name: toPosixPath(filename), size: stats.size, mode: stats.mode }, data)
.then ->
preFinalizeCallback?(pack)
.then ->
pack.finalize()
return pack
truncateString = (str, len) ->
return str if str.length < len
str = str.slice(0, len)
# return everything up to the last line. this is a cheeky way to avoid
# having to deal with splitting the string midway through some special
# character sequence.
return str.slice(0, str.lastIndexOf('\n'))
LOG_LENGTH_MAX = 512 * 1024 # 512KB
exports.buildProject = (
docker, logger,
projectPath, projectName, composition,
arch, deviceType,
emulated, buildOpts,
inlineLogs
) ->
_ = require('lodash')
humanize = require('humanize')
compose = require('resin-compose-parse')
builder = require('resin-multibuild')
transpose = require('docker-qemu-transpose')
{ BALENA_ENGINE_TMP_PATH } = require('../config')
{ checkBuildSecretsRequirements, makeBuildTasks } = require('./compose_ts')
qemu = require('./qemu-ts')
{ toPosixPath } = builder.PathUtils
logger.logInfo("Building for #{arch}/#{deviceType}")
imageDescriptors = compose.parse(composition)
imageDescriptorsByServiceName = _.keyBy(imageDescriptors, 'serviceName')
if inlineLogs
renderer = new BuildProgressInline(logger.streams['build'], imageDescriptors)
else
tty = require('./tty')(process.stdout)
renderer = new BuildProgressUI(tty, imageDescriptors)
renderer.start()
Promise.resolve(checkBuildSecretsRequirements(docker, projectPath))
.then -> qemu.installQemuIfNeeded(emulated, logger, arch, docker)
.tap (needsQemu) ->
return if not needsQemu
logger.logInfo('Emulation is enabled')
# Copy qemu into all build contexts
Promise.map imageDescriptors, (d) ->
return if not d.image.context? # external image
return qemu.copyQemu(path.join(projectPath, d.image.context), arch)
.then (needsQemu) ->
# Tar up the directory, ready for the build stream
tarDirectory(projectPath)
.then (tarStream) ->
Promise.resolve(makeBuildTasks(composition, tarStream, { arch, deviceType }, logger))
.map (task) ->
d = imageDescriptorsByServiceName[task.serviceName]
# multibuild parses the composition internally so any tags we've
# set before are lost; re-assign them here
task.tag ?= [ projectName, task.serviceName ].join('_').toLowerCase()
if d.image.context?
d.image.tag = task.tag
# configure build opts appropriately
task.dockerOpts ?= {}
_.merge(task.dockerOpts, buildOpts, { t: task.tag })
if d.image.context?.args?
task.dockerOpts.buildargs ?= {}
_.merge(task.dockerOpts.buildargs, d.image.context.args)
# Get the service-specific log stream
# Caveat: `multibuild.BuildTask` defines no `logStream` property
# but it's convenient to store it there; it's JS ultimately.
task.logStream = renderer.streams[task.serviceName]
task.logBuffer = []
# Setup emulation if needed
return [ task, null ] if task.external or not needsQemu
binPath = qemu.qemuPathInContext(path.join(projectPath, task.context))
transpose.transposeTarStream task.buildStream,
hostQemuPath: toPosixPath(binPath)
containerQemuPath: "/tmp/#{qemu.QEMU_BIN_NAME}"
qemuFileMode: 0o555
.then (stream) ->
task.buildStream = stream
.return([ task, binPath ])
.map ([ task, qemuPath ]) ->
Promise.resolve(task).tap (task) ->
captureStream = buildLogCapture(task.external, task.logBuffer)
if task.external
# External image -- there's no build to be performed,
# just follow pull progress.
captureStream.pipe(task.logStream)
task.progressHook = pullProgressAdapter(captureStream)
else
task.streamHook = (stream) ->
stream = createLogStream(stream)
if qemuPath?
buildThroughStream = transpose.getBuildThroughStream
hostQemuPath: toPosixPath(qemuPath)
containerQemuPath: "/tmp/#{qemu.QEMU_BIN_NAME}"
rawStream = stream.pipe(buildThroughStream)
else
rawStream = stream
# `stream` sends out raw strings in contrast to `task.progressHook`
# where we're given objects. capture these strings as they come
# before we parse them.
rawStream
.pipe(dropEmptyLinesStream())
.pipe(captureStream)
.pipe(buildProgressAdapter(inlineLogs))
.pipe(task.logStream)
.then (tasks) ->
logger.logDebug 'Prepared tasks; building...'
Promise.resolve(builder.performBuilds(tasks, docker, BALENA_ENGINE_TMP_PATH))
.map (builtImage) ->
if not builtImage.successful
builtImage.error.serviceName = builtImage.serviceName
throw builtImage.error
d = imageDescriptorsByServiceName[builtImage.serviceName]
task = _.find(tasks, serviceName: builtImage.serviceName)
image =
serviceName: d.serviceName
name: d.image.tag ? d.image
logs: truncateString(task.logBuffer.join('\n'), LOG_LENGTH_MAX)
props:
dockerfile: builtImage.dockerfile
projectType: builtImage.projectType
# Times here are timestamps, so test whether they're null
# before creating a date out of them, as `new Date(null)`
# creates a date representing UNIX time 0.
if (startTime = builtImage.startTime)
image.props.startTime = new Date(startTime)
if (endTime = builtImage.endTime)
image.props.endTime = new Date(endTime)
docker.getImage(image.name).inspect().get('Size').then (size) ->
image.props.size = size
.return(image)
.tap (images) ->
summary = _(images).map ({ serviceName, props }) ->
[ serviceName, "Image size: #{humanize.filesize(props.size)}" ]
.fromPairs()
.value()
renderer.end(summary)
.finally(renderer.end)
createRelease = (apiEndpoint, auth, userId, appId, composition) ->
_ = require('lodash')
crypto = require('crypto')
releaseMod = require('resin-release')
client = releaseMod.createClient({ apiEndpoint, auth })
releaseMod.create
client: client
user: userId
application: appId
composition: composition
source: 'local'
commit: crypto.pseudoRandomBytes(16).toString('hex').toLowerCase()
.then ({ release, serviceImages }) ->
release = _.omit(release, [
'created_at'
'belongs_to__application'
'is_created_by__user'
'__metadata'
])
serviceImages = _.mapValues serviceImages, (serviceImage) ->
_.omit(serviceImage, [
'created_at'
'is_a_build_of__service'
'__metadata'
])
return { client, release, serviceImages }
tagServiceImages = (docker, images, serviceImages) ->
Promise.map images, (d) ->
serviceImage = serviceImages[d.serviceName]
imageName = serviceImage.is_stored_at__image_location
# coffeelint: disable-next-line=check_scope ("Variable is assigned to but never read")
[ _match, registry, repo, tag = 'latest' ] = /(.*?)\/(.*?)(?::([^/]*))?$/.exec(imageName)
name = "#{registry}/#{repo}"
docker.getImage(d.name).tag({ repo: name, tag, force: true })
.then ->
docker.getImage("#{name}:#{tag}")
.then (localImage) ->
serviceName: d.serviceName
serviceImage: serviceImage
localImage: localImage
registry: registry
repo: repo
logs: d.logs
props: d.props
getPreviousRepos = (sdk, docker, logger, appID) ->
sdk.pine.get(
resource: 'release'
options:
$filter:
belongs_to__application: appID
status: 'success'
$select:
[ 'id' ]
$expand:
contains__image:
$expand: 'image'
$orderby: 'id desc'
$top: 1
)
.then (release) ->
# grab all images from the latest release, return all image locations in the registry
if release?.length > 0
images = release[0].contains__image
Promise.map images, (d) ->
imageName = d.image[0].is_stored_at__image_location
docker.getRegistryAndName(imageName)
.then ( registry ) ->
logger.logDebug("Requesting access to previously pushed image repo (#{registry.imageName})")
return registry.imageName
.catch (e) ->
logger.logDebug("Failed to access previously pushed image repo: #{e}")
authorizePush = (sdk, logger, tokenAuthEndpoint, registry, images, previousRepos) ->
_ = require('lodash')
if not _.isArray(images)
images = [ images ]
images.push previousRepos...
sdk.request.send
baseUrl: tokenAuthEndpoint
url: '/auth/v1/token'
qs:
service: registry
scope: images.map (repo) ->
"repository:#{repo}:pull,push"
.get('body')
.get('token')
.catchReturn({})
pushAndUpdateServiceImages = (docker, token, images, afterEach) ->
chalk = require('chalk')
{ DockerProgress } = require('docker-progress')
{ retry } = require('./helpers')
tty = require('./tty')(process.stdout)
opts = { authconfig: registrytoken: token }
progress = new DockerProgress(dockerToolbelt: docker)
renderer = pushProgressRenderer(tty, chalk.blue('[Push]') + ' ')
reporters = progress.aggregateProgress(images.length, renderer)
Promise.using tty.cursorHidden(), ->
Promise.map images, ({ serviceImage, localImage, props, logs }, index) ->
Promise.join(
localImage.inspect().get('Size')
retry(
-> progress.push(localImage.name, reporters[index], opts)
3 # `times` - retry 3 times
localImage.name # `label` included in retry log messages
2000 # `delayMs` - wait 2 seconds before the 1st retry
1.4 # `backoffScaler` - wait multiplier for each retry
).finally(renderer.end)
(size, digest) ->
serviceImage.image_size = size
serviceImage.content_hash = digest
serviceImage.build_log = logs
serviceImage.dockerfile = props.dockerfile
serviceImage.project_type = props.projectType
serviceImage.start_timestamp = props.startTime if props.startTime
serviceImage.end_timestamp = props.endTime if props.endTime
serviceImage.push_timestamp = new Date()
serviceImage.status = 'success'
)
.tapCatch (e) ->
serviceImage.error_message = '' + e
serviceImage.status = 'failed'
.finally ->
afterEach?(serviceImage, props)
exports.deployProject = (
docker, logger,
composition, images,
appId, userId, auth,
apiEndpoint,
skipLogUpload
) ->
_ = require('lodash')
chalk = require('chalk')
releaseMod = require('resin-release')
tty = require('./tty')(process.stdout)
prefix = chalk.cyan('[Info]') + ' '
spinner = createSpinner()
runloop = runSpinner(tty, spinner, "#{prefix}Creating release...")
createRelease(apiEndpoint, auth, userId, appId, composition)
.finally(runloop.end)
.then ({ client, release, serviceImages }) ->
logger.logDebug('Tagging images...')
tagServiceImages(docker, images, serviceImages)
.tap (images) ->
logger.logDebug('Authorizing push...')
sdk = require('balena-sdk').fromSharedOptions()
getPreviousRepos(sdk, docker, logger, appId)
.then (previousRepos) ->
authorizePush(sdk, logger, apiEndpoint, images[0].registry, _.map(images, 'repo'), previousRepos)
.then (token) ->
logger.logInfo('Pushing images to registry...')
pushAndUpdateServiceImages docker, token, images, (serviceImage) ->
logger.logDebug("Saving image #{serviceImage.is_stored_at__image_location}")
if skipLogUpload
delete serviceImage.build_log
releaseMod.updateImage(client, serviceImage.id, serviceImage)
.finally ->
logger.logDebug('Untagging images...')
Promise.map images, ({ localImage }) ->
localImage.remove()
.then ->
release.status = 'success'
.tapCatch ->
release.status = 'failed'
.finally ->
runloop = runSpinner(tty, spinner, "#{prefix}Saving release...")
release.end_timestamp = new Date()
releaseMod.updateRelease(client, release.id, release)
.finally(runloop.end)
.return(release)
# utilities
renderProgressBar = (percentage, stepCount) ->
_ = require('lodash')
percentage = _.clamp(percentage, 0, 100)
barCount = stepCount * percentage // 100
spaceCount = stepCount - barCount
bar = "[#{_.repeat('=', barCount)}>#{_.repeat(' ', spaceCount)}]"
return "#{bar} #{_.padStart(percentage, 3)}%"
pushProgressRenderer = (tty, prefix) ->
fn = (e) ->
{ error, percentage } = e
throw new Error(error) if error?
bar = renderProgressBar(percentage, 40)
tty.replaceLine("#{prefix}#{bar}\r")
fn.end = ->
tty.clearLine()
return fn
createLogStream = (input) ->
split = require('split')
stripAnsi = require('strip-ansi-stream')
return input.pipe(stripAnsi()).pipe(split())
dropEmptyLinesStream = ->
through = require('through2')
through (data, enc, cb) ->
str = data.toString('utf-8')
@push(str) if str.trim()
cb()
buildLogCapture = (objectMode, buffer) ->
through = require('through2')
through { objectMode }, (data, enc, cb) ->
# data from pull stream
if data.error
buffer.push("#{data.error}")
else if data.progress and data.status
buffer.push("#{data.progress}% #{data.status}")
else if data.status
buffer.push("#{data.status}")
# data from build stream
else
buffer.push(data)
cb(null, data)
buildProgressAdapter = (inline) ->
through = require('through2')
stepRegex = /^\s*Step\s+(\d+)\/(\d+)\s*: (.+)$/
[ step, numSteps, progress ] = [ null, null, undefined ]
through { objectMode: true }, (str, enc, cb) ->
return cb(null, str) if not str?
if inline
return cb(null, { status: str })
if /^Successfully tagged /.test(str)
progress = undefined
else
if (match = stepRegex.exec(str))
step = match[1]
numSteps ?= match[2]
str = match[3]
if step?
str = "Step #{step}/#{numSteps}: #{str}"
progress = parseInt(step, 10) * 100 // parseInt(numSteps, 10)
cb(null, { status: str, progress })
pullProgressAdapter = (outStream) ->
return ({ status, id, percentage, error, errorDetail }) ->
if status?
status = status.replace(/^Status: /, '')
if id?
status = "#{id}: #{status}"
if percentage is 100
percentage = undefined
outStream.write
status: status
progress: percentage
error: errorDetail?.message ? error
createSpinner = ->
chars = '|/-\\'
index = 0
-> chars[(index++) % chars.length]
runSpinner = (tty, spinner, msg) ->
runloop = createRunLoop ->
tty.clearLine()
tty.writeLine("#{msg} #{spinner()}")
tty.cursorUp()
runloop.onEnd = ->
tty.clearLine()
tty.writeLine(msg)
return runloop
createRunLoop = (tick) ->
timerId = setInterval(tick, 1000 / 10)
runloop = {
onEnd: ->
end: ->
clearInterval(timerId)
runloop.onEnd()
}
return runloop
class BuildProgressUI
constructor: (tty, descriptors) ->
_ = require('lodash')
chalk = require('chalk')
through = require('through2')
eventHandler = @_handleEvent
services = _.map(descriptors, 'serviceName')
streams = _(services).map (service) ->
stream = through.obj (event, _enc, cb) ->
eventHandler(service, event)
cb()
stream.pipe(tty.stream, end: false)
[ service, stream ]
.fromPairs()
.value()
@_tty = tty
@_serviceToDataMap = {}
@_services = services
# Logger magically prefixes the log line with [Build] etc., but it doesn't
# work well with the spinner we're also showing. Manually build the prefix
# here and bypass the logger.
prefix = chalk.blue('[Build]') + ' '
offset = 10 # account for escape sequences inserted for colouring
@_prefixWidth = offset + prefix.length + _.max(_.map(services, 'length'))
@_prefix = prefix
# these are to handle window wrapping
@_maxLineWidth = null
@_lineWidths = []
@_startTime = null
@_ended = false
@_cancelled = false
@_spinner = createSpinner()
@streams = streams
_handleEvent: (service, event) =>
@_serviceToDataMap[service] = event
_handleInterrupt: =>
@_cancelled = true
@end()
process.exit(130) # 128 + SIGINT
start: =>
process.on('SIGINT', @_handleInterrupt)
@_tty.hideCursor()
@_services.forEach (service) =>
@streams[service].write({ status: 'Preparing...' })
@_runloop = createRunLoop(@_display)
@_startTime = Date.now()
end: (summary = null) =>
return if @_ended
@_ended = true
process.removeListener('SIGINT', @_handleInterrupt)
@_runloop.end()
@_runloop = null
@_clear()
@_renderStatus(true)
@_renderSummary(summary ? @_getServiceSummary())
@_tty.showCursor()
_display: =>
@_clear()
@_renderStatus()
@_renderSummary(@_getServiceSummary())
@_tty.cursorUp(@_services.length + 1) # for status line
_clear: ->
@_tty.deleteToEnd()
@_maxLineWidth = @_tty.currentWindowSize().width
_getServiceSummary: ->
_ = require('lodash')
services = @_services
serviceToDataMap = @_serviceToDataMap
_(services).map (service) ->
{ status, progress, error } = serviceToDataMap[service] ? {}
if error
return "#{error}"
else if progress
bar = renderProgressBar(progress, 20)
return "#{bar} #{status}" if status
return "#{bar}"
else if status
return "#{status}"
else
return 'Waiting...'
.map (data, index) ->
[ services[index], data ]
.fromPairs()
.value()
_renderStatus: (end = false) ->
moment = require('moment')
require('moment-duration-format')(moment)
@_tty.clearLine()
@_tty.write(@_prefix)
if end and @_cancelled
@_tty.writeLine('Build cancelled')
else if end
serviceCount = @_services.length
serviceStr = if serviceCount is 1 then '1 service' else "#{serviceCount} services"
runTime = Date.now() - @_startTime
durationStr = moment.duration(runTime // 1000, 'seconds').format()
@_tty.writeLine("Built #{serviceStr} in #{durationStr}")
else
@_tty.writeLine("Building services... #{@_spinner()}")
_renderSummary: (serviceToStrMap) ->
_ = require('lodash')
chalk = require('chalk')
truncate = require('cli-truncate')
strlen = require('string-width')
@_services.forEach (service, index) =>
str = _.padEnd(@_prefix + chalk.bold(service), @_prefixWidth)
str += serviceToStrMap[service]
if @_maxLineWidth?
str = truncate(str, @_maxLineWidth)
@_lineWidths[index] = strlen(str)
@_tty.clearLine()
@_tty.writeLine(str)
class BuildProgressInline
constructor: (outStream, descriptors) ->
_ = require('lodash')
through = require('through2')
services = _.map(descriptors, 'serviceName')
eventHandler = @_renderEvent
streams = _(services).map (service) ->
stream = through.obj (event, _enc, cb) ->
eventHandler(service, event)
cb()
stream.pipe(outStream, end: false)
[ service, stream ]
.fromPairs()
.value()
offset = 10 # account for escape sequences inserted for colouring
@_prefixWidth = offset + _.max(_.map(services, 'length'))
@_outStream = outStream
@_services = services
@_startTime = null
@_ended = false
@streams = streams
start: =>
@_outStream.write('Building services...\n')
@_services.forEach (service) =>
@streams[service].write({ status: 'Preparing...' })
@_startTime = Date.now()
end: (summary = null) =>
moment = require('moment')
require('moment-duration-format')(moment)
return if @_ended
@_ended = true
if summary?
@_services.forEach (service) =>
@_renderEvent(service, summary[service])
if @_cancelled
@_outStream.write('Build cancelled\n')
else
serviceCount = @_services.length
serviceStr = if serviceCount is 1 then '1 service' else "#{serviceCount} services"
runTime = Date.now() - @_startTime
durationStr = moment.duration(runTime // 1000, 'seconds').format()
@_outStream.write("Built #{serviceStr} in #{durationStr}\n")
_renderEvent: (service, event) =>
_ = require('lodash')
chalk = require('chalk')
str = do ->
{ status, error } = event
if error
return "#{error}"
else if status
return "#{status}"
else
return 'Waiting...'
prefix = _.padEnd(chalk.bold(service), @_prefixWidth)
@_outStream.write(prefix)
@_outStream.write(str)
@_outStream.write('\n')