devserver.py

#!/usr/bin/python

# Copyright (c) 2009-2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Chromium OS development server that can be used for all forms of update.

This devserver can be used to perform system-wide autoupdate and update
of specific portage packages on devices running Chromium OS derived operating
systems. It mainly operates in two modes:

1) archive mode: In this mode, the devserver is configured to stage and
serve artifacts from Google Storage using the credentials provided to it before
it is run. The easiest way to understand this is that the devserver is
functioning as a local cache for artifacts produced and uploaded by build
servers. Users of this form of devserver can either download the artifacts
from the devservers static directory OR use the update RPC to perform a
system-wide autoupdate. Archive mode is always active.

2) artifact-generation mode: in this mode, the devserver will attempt to
generate update payloads and build artifacts when requested. This mode only
works in the Chromium OS chroot as it uses build tools only present in the
chroot (emerge, cros_generate_update_payload, etc.). By default, when a device
requests an update from this form of devserver, the devserver will attempt to
discover if a more recent build of the board has been built by the developer
and generate a payload that the requested system can autoupdate to. In addition,
it accepts gmerge requests from devices that will stage the newest version of
a particular package from a developer's chroot onto a requesting device. Note
if archive_dir is specified, this mode is disabled.

For example:
gmerge gmerge -d <devserver_url>

devserver will see if a newer package of gmerge is available. If gmerge is
cros_work'd on, it will re-build gmerge. After this, gmerge will install that
version of gmerge that the devserver just created/found.

For autoupdates, there are many more advanced options that can help specify
how to update and which payload to give to a requester.
"""


import json
import optparse
import os
import re
import shutil
import socket
import subprocess
import sys
import tempfile
import threading
import types
from logging import handlers

import cherrypy
import cherrypy._cplogging

import autoupdate
import common_util
import downloader
import log_util
import xbuddy

# Module-local log function.
def _Log(message, *args):
  return log_util.LogWithTag('DEVSERVER', message, *args)


CACHED_ENTRIES = 12

TELEMETRY_FOLDER = 'telemetry_src'
TELEMETRY_DEPS = ['dep-telemetry_dep.tar.bz2',
                  'dep-page_cycler_dep.tar.bz2',
                  'dep-chrome_test.tar.bz2',
                  'dep-perf_data_dep.tar.bz2']

# Sets up global to share between classes.
updater = None

# Log rotation parameters.  These settings correspond to once a week
# at midnight between Friday and Saturday, with about three months
# of old logs kept for backup.
#
# For more, see the documentation for
# logging.handlers.TimedRotatingFileHandler
_LOG_ROTATION_TIME = 'W4'
_LOG_ROTATION_BACKUP = 13


class DevServerError(Exception):
  """Exception class used by this module."""
  pass


def _LeadingWhiteSpaceCount(string):
  """Count the amount of leading whitespace in a string.

  Args:
    string: The string to count leading whitespace in.
  Returns:
    number of white space chars before characters start.
  """
  matched = re.match('^\s+', string)
  if matched:
    return len(matched.group())

  return 0


def _PrintDocStringAsHTML(func):
  """Make a functions docstring somewhat HTML style.

  Args:
    func: The function to return the docstring from.
  Returns:
    A string that is somewhat formated for a web browser.
  """
  # TODO(scottz): Make this parse Args/Returns in a prettier way.
  # Arguments could be bolded and indented etc.
  html_doc = []
  for line in func.__doc__.splitlines():
    leading_space = _LeadingWhiteSpaceCount(line)
    if leading_space > 0:
      line = '&nbsp;' * leading_space + line

    html_doc.append('<BR>%s' % line)

  return '\n'.join(html_doc)


def _GetConfig(options):
  """Returns the configuration for the devserver."""

  # On a system with IPv6 not compiled into the kernel,
  # AF_INET6 sockets will return a socket.error exception.
  # On such systems, fall-back to IPv4.
  socket_host = '::'
  try:
    socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
  except socket.error:
    socket_host = '0.0.0.0'

  base_config = { 'global':
                  { 'server.log_request_headers': True,
                    'server.protocol_version': 'HTTP/1.1',
                    'server.socket_host': socket_host,
                    'server.socket_port': int(options.port),
                    'response.timeout': 6000,
                    'request.show_tracebacks': True,
                    'server.socket_timeout': 60,
                    'tools.staticdir.root':
                      os.path.dirname(os.path.abspath(sys.argv[0])),
                  },
                  '/api':
                  {
                    # Gets rid of cherrypy parsing post file for args.
                    'request.process_request_body': False,
                  },
                  '/build':
                  {
                    'response.timeout': 100000,
                  },
                  '/update':
                  {
                    # Gets rid of cherrypy parsing post file for args.
                    'request.process_request_body': False,
                    'response.timeout': 10000,
                  },
                  # Sets up the static dir for file hosting.
                  '/static':
                  { 'tools.staticdir.dir': 'static',
                    'tools.staticdir.on': True,
                    'response.timeout': 10000,
                  },
                }
  if options.production:
    base_config['global'].update({'server.thread_pool': 75})

  return base_config


def _PrepareToServeUpdatesOnly(image_dir, static_dir):
  """Sets up symlink to image_dir for serving purposes."""
  assert os.path.exists(image_dir), '%s must exist.' % image_dir
  # If  we're  serving  out  of  an archived  build  dir  (e.g.  a
  # buildbot), prepare this webserver's magic 'static/' dir with a
  # link to the build archive.
  _Log('Preparing autoupdate for "serve updates only" mode.')
  if os.path.lexists('%s/archive' % static_dir):
    if image_dir != os.readlink('%s/archive' % static_dir):
      _Log('removing stale symlink to %s' % image_dir)
      os.unlink('%s/archive' % static_dir)
      os.symlink(image_dir, '%s/archive' % static_dir)

  else:
    os.symlink(image_dir, '%s/archive' % static_dir)

  _Log('archive dir: %s ready to be used to serve images.' % image_dir)


def _GetRecursiveMemberObject(root, member_list):
  """Returns an object corresponding to a nested member list.

  Args:
    root: the root object to search
    member_list: list of nested members to search
  Returns:
    An object corresponding to the member name list; None otherwise.
  """
  for member in member_list:
    next_root = root.__class__.__dict__.get(member)
    if not next_root:
      return None
    root = next_root
  return root


def _IsExposed(name):
  """Returns True iff |name| has an `exposed' attribute and it is set."""
  return hasattr(name, 'exposed') and name.exposed


def _GetExposedMethod(root, nested_member, ignored=None):
  """Returns a CherryPy-exposed method, if such exists.

  Args:
    root: the root object for searching
    nested_member: a slash-joined path to the nested member
    ignored: method paths to be ignored
  Returns:
    A function object corresponding to the path defined by |member_list| from
    the |root| object, if the function is exposed and not ignored; None
    otherwise.
  """
  method = (not (ignored and nested_member in ignored) and
            _GetRecursiveMemberObject(root, nested_member.split('/')))
  if (method and type(method) == types.FunctionType and _IsExposed(method)):
    return method


def _FindExposedMethods(root, prefix, unlisted=None):
  """Finds exposed CherryPy methods.

  Args:
    root: the root object for searching
    prefix: slash-joined chain of members leading to current object
    unlisted: URLs to be excluded regardless of their exposed status
  Returns:
    List of exposed URLs that are not unlisted.
  """
  method_list = []
  for member in sorted(root.__class__.__dict__.keys()):
    prefixed_member = prefix + '/' + member if prefix else member
    if unlisted and prefixed_member in unlisted:
      continue
    member_obj = root.__class__.__dict__[member]
    if _IsExposed(member_obj):
      if type(member_obj) == types.FunctionType:
        method_list.append(prefixed_member)
      else:
        method_list += _FindExposedMethods(
            member_obj, prefixed_member, unlisted)
  return method_list


class ApiRoot(object):
  """RESTful API for Dev Server information."""
  exposed = True

  @cherrypy.expose
  def hostinfo(self, ip):
    """Returns a JSON dictionary containing information about the given ip.

    Args:
      ip: address of host whose info is requested
    Returns:
      A JSON dictionary containing all or some of the following fields:
        last_event_type (int):        last update event type received
        last_event_status (int):      last update event status received
        last_known_version (string):  last known version reported in update ping
        forced_update_label (string): update label to force next update ping to
                                      use, set by setnextupdate
      See the OmahaEvent class in update_engine/omaha_request_action.h for
      event type and status code definitions. If the ip does not exist an empty
      string is returned.

    Example URL:
      http://myhost/api/hostinfo?ip=192.168.1.5
    """
    return updater.HandleHostInfoPing(ip)

  @cherrypy.expose
  def hostlog(self, ip):
    """Returns a JSON object containing a log of host event.

    Args:
      ip: address of host whose event log is requested, or `all'
    Returns:
      A JSON encoded list (log) of dictionaries (events), each of which
      containing a `timestamp' and other event fields, as described under
      /api/hostinfo.

    Example URL:
      http://myhost/api/hostlog?ip=192.168.1.5
    """
    return updater.HandleHostLogPing(ip)

  @cherrypy.expose
  def setnextupdate(self, ip):
    """Allows the response to the next update ping from a host to be set.

    Takes the IP of the host and an update label as normally provided to the
    /update command.
    """
    body_length = int(cherrypy.request.headers['Content-Length'])
    label = cherrypy.request.rfile.read(body_length)

    if label:
      label = label.strip()
      if label:
        return updater.HandleSetUpdatePing(ip, label)
    raise cherrypy.HTTPError(400, 'No label provided.')


  @cherrypy.expose
  def fileinfo(self, *path_args):
    """Returns information about a given staged file.

    Args:
      path_args: path to the file inside the server's static staging directory
    Returns:
      A JSON encoded dictionary with information about the said file, which may
      contain the following keys/values:
        size (int):      the file size in bytes
        sha1 (string):   a base64 encoded SHA1 hash
        sha256 (string): a base64 encoded SHA256 hash

    Example URL:
      http://myhost/api/fileinfo/some/path/to/file
    """
    file_path = os.path.join(updater.static_dir, *path_args)
    if not os.path.exists(file_path):
      raise DevServerError('file not found: %s' % file_path)
    try:
      file_size = os.path.getsize(file_path)
      file_sha1 = common_util.GetFileSha1(file_path)
      file_sha256 = common_util.GetFileSha256(file_path)
    except os.error, e:
      raise DevServerError('failed to get info for file %s: %s' %
                           (file_path, e))

    is_delta = autoupdate.Autoupdate.IsDeltaFormatFile(file_path)

    return json.dumps({
        autoupdate.Autoupdate.SIZE_ATTR: file_size,
        autoupdate.Autoupdate.SHA1_ATTR: file_sha1,
        autoupdate.Autoupdate.SHA256_ATTR: file_sha256,
        autoupdate.Autoupdate.ISDELTA_ATTR: is_delta
    })


class DevServerRoot(object):
  """The Root Class for the Dev Server.

  CherryPy works as follows:
    For each method in this class, cherrpy interprets root/path
    as a call to an instance of DevServerRoot->method_name.  For example,
    a call to http://myhost/build will call build.  CherryPy automatically
    parses http args and places them as keyword arguments in each method.
    For paths http://myhost/update/dir1/dir2, you can use *args so that
    cherrypy uses the update method and puts the extra paths in args.
  """
  # Method names that should not be listed on the index page.
  _UNLISTED_METHODS = ['index', 'doc']

  api = ApiRoot()

  # Number of threads that devserver is staging images.
  _staging_thread_count = 0
  # Lock used to lock increasing/decreasing count.
  _staging_thread_count_lock = threading.Lock()

  def __init__(self, _xbuddy):
    self._builder = None
    self._telemetry_lock_dict = common_util.LockDict()
    self._xbuddy = _xbuddy

  @cherrypy.expose
  def build(self, board, pkg, **kwargs):
    """Builds the package specified."""
    import builder
    if self._builder is None:
      self._builder = builder.Builder()
    return self._builder.Build(board, pkg, kwargs)

  @staticmethod
  def _canonicalize_archive_url(archive_url):
    """Canonicalizes archive_url strings.

    Raises:
      DevserverError: if archive_url is not set.
    """
    if archive_url:
      if not archive_url.startswith('gs://'):
        raise DevServerError("Archive URL isn't from Google Storage.")

      return archive_url.rstrip('/')
    else:
      raise DevServerError("Must specify an archive_url in the request")

  @cherrypy.expose
  def download(self, **kwargs):
    """Downloads and archives full/delta payloads from Google Storage.

    THIS METHOD IS DEPRECATED: use stage(..., artifacts=...) instead.
    This methods downloads artifacts. It may download artifacts in the
    background in which case a caller should call wait_for_status to get
    the status of the background artifact downloads. They should use the same
    args passed to download.

    Args:
      archive_url: Google Storage URL for the build.

    Example URL:
      http://myhost/download?archive_url=gs://chromeos-image-archive/
      x86-generic/R17-1208.0.0-a1-b338
    """
    return self.stage(archive_url=kwargs.get('archive_url'),
                      artifacts='full_payload,test_suites,stateful')


  @cherrypy.expose
  def stage(self, **kwargs):
    """Downloads and caches the artifacts from Google Storage URL.

    Downloads and caches the artifacts Google Storage URL. Returns once these
    have been downloaded on the devserver. A call to this will attempt to cache
    non-specified artifacts in the background for the given from the given URL
    following the principle of spatial locality. Spatial locality of different
    artifacts is explicitly defined in the build_artifact module.

    These artifacts will then be available from the static/ sub-directory of
    the devserver.

    Args:
      archive_url: Google Storage URL for the build.
      artifacts: Comma separated list of artifacts to download.

    Example:
      To download the autotest and test suites tarballs:
        http://devserver_url:<port>/stage?archive_url=gs://your_url/path&
            artifacts=autotest,test_suites
      To download the full update payload:
        http://devserver_url:<port>/stage?archive_url=gs://your_url/path&
            artifacts=full_payload

      For both these examples, one could find these artifacts at:
        http://devserver_url:<port>/static/archive/<relative_path>*

      Note for this example, relative path is the archive_url stripped of its
      basename i.e. path/ in the examples above. Specific example:

      gs://chromeos-image-archive/x86-mario-release/R26-3920.0.0

      Will get staged to:

      http://devserver_url:<port>/static/archive/x86-mario-release/R26-3920.0.0
    """
    archive_url = self._canonicalize_archive_url(kwargs.get('archive_url'))
    artifacts = kwargs.get('artifacts', '')
    if not artifacts:
      raise DevServerError('No artifacts specified.')

    with DevServerRoot._staging_thread_count_lock:
      DevServerRoot._staging_thread_count += 1
    try:
      downloader.Downloader(updater.static_dir, archive_url).Download(
          artifacts.split(','))
    finally:
      with DevServerRoot._staging_thread_count_lock:
        DevServerRoot._staging_thread_count -= 1
    return 'Success'


  @cherrypy.expose
  def setup_telemetry(self, **kwargs):
    """Extracts and sets up telemetry

    This method goes through the telemetry deps packages, and stages them on
    the devserver to be used by the drones and the telemetry tests.

    Args:
      archive_url: Google Storage URL for the build.

    Returns:
      Path to the source folder for the telemetry codebase once it is staged.
    """
    archive_url = kwargs.get('archive_url')
    self.stage(archive_url=archive_url, artifacts='autotest')

    build = '/'.join(downloader.Downloader.ParseUrl(archive_url))
    build_path = os.path.join(updater.static_dir, build)
    deps_path = os.path.join(build_path, 'autotest/packages')
    telemetry_path = os.path.join(build_path, TELEMETRY_FOLDER)
    src_folder = os.path.join(telemetry_path, 'src')

    with self._telemetry_lock_dict.lock(telemetry_path):
      if os.path.exists(src_folder):
        # Telemetry is already fully stage return
        return src_folder

      common_util.MkDirP(telemetry_path)

      # Copy over the required deps tar balls to the telemetry directory.
      for dep in TELEMETRY_DEPS:
        dep_path = os.path.join(deps_path, dep)
        if not os.path.exists(dep_path):
          # This dep does not exist (could be new), do not extract it.
          continue
        try:
          common_util.ExtractTarball(dep_path, telemetry_path)
        except common_util.CommonUtilError as e:
          shutil.rmtree(telemetry_path)
          raise DevServerError(str(e))

      # By default all the tarballs extract to test_src but some parts of
      # the telemetry code specifically hardcoded to exist inside of 'src'.
      test_src = os.path.join(telemetry_path, 'test_src')
      try:
        shutil.move(test_src, src_folder)
      except shutil.Error:
        # This can occur if src_folder already exists. Remove and retry move.
        shutil.rmtree(src_folder)
        raise DevServerError('Failure in telemetry setup for build %s. Appears'
                             ' that the test_src to src move failed.' % build)

      return src_folder

  @cherrypy.expose
  def wait_for_status(self, **kwargs):
    """Waits for background artifacts to be downloaded from Google Storage.

    THIS METHOD IS DEPRECATED: use stage(..., artifacts=...) instead.
    Args:
      archive_url: Google Storage URL for the build.

    Example URL:
      http://myhost/wait_for_status?archive_url=gs://chromeos-image-archive/
      x86-generic/R17-1208.0.0-a1-b338
    """
    return self.stage(archive_url=kwargs.get('archive_url'),
                      artifacts='full_payload,test_suites,autotest,stateful')

  @cherrypy.expose
  def stage_debug(self, **kwargs):
    """Downloads and stages debug symbol payloads from Google Storage.

    THIS METHOD IS DEPRECATED: use stage(..., artifacts=...) instead.
    This methods downloads the debug symbol build artifact
    synchronously, and then stages it for use by symbolicate_dump.

    Args:
      archive_url: Google Storage URL for the build.

    Example URL:
      http://myhost/stage_debug?archive_url=gs://chromeos-image-archive/
      x86-generic/R17-1208.0.0-a1-b338
    """
    return self.stage(archive_url=kwargs.get('archive_url'),
                      artifacts='symbols')

  @cherrypy.expose
  def symbolicate_dump(self, minidump, **kwargs):
    """Symbolicates a minidump using pre-downloaded symbols, returns it.

    Callers will need to POST to this URL with a body of MIME-type
    "multipart/form-data".
    The body should include a single argument, 'minidump', containing the
    binary-formatted minidump to symbolicate.

    Args:
      archive_url: Google Storage URL for the build.
      minidump: The binary minidump file to symbolicate.
    """
    # Ensure the symbols have been staged.
    archive_url = self._canonicalize_archive_url(kwargs.get('archive_url'))
    if self.stage(archive_url=archive_url, artifacts='symbols') != 'Success':
      raise DevServerError('Failed to stage symbols for %s' % archive_url)

    to_return = ''
    with tempfile.NamedTemporaryFile() as local:
      while True:
        data = minidump.file.read(8192)
        if not data:
          break
        local.write(data)

      local.flush()

      symbols_directory = os.path.join(downloader.Downloader.GetBuildDir(
          updater.static_dir, archive_url), 'debug', 'breakpad')

      stackwalk = subprocess.Popen(
          ['minidump_stackwalk', local.name, symbols_directory],
          stdout=subprocess.PIPE, stderr=subprocess.PIPE)

      to_return, error_text = stackwalk.communicate()
      if stackwalk.returncode != 0:
        raise DevServerError("Can't generate stack trace: %s (rc=%d)" % (
            error_text, stackwalk.returncode))

    return to_return

  @cherrypy.expose
  def latestbuild(self, **params):
    """Return a string representing the latest build for a given target.

    Args:
      target: The build target, typically a combination of the board and the
          type of build e.g. x86-mario-release.
      milestone: The milestone to filter builds on. E.g. R16. Optional, if not
          provided the latest RXX build will be returned.
    Returns:
      A string representation of the latest build if one exists, i.e.
          R19-1993.0.0-a1-b1480.
      An empty string if no latest could be found.
    """
    if not params:
      return _PrintDocStringAsHTML(self.latestbuild)

    if 'target' not in params:
      raise cherrypy.HTTPError('500 Internal Server Error',
                               'Error: target= is required!')
    try:
      return common_util.GetLatestBuildVersion(
          updater.static_dir, params['target'],
          milestone=params.get('milestone'))
    except common_util.CommonUtilError as errmsg:
      raise cherrypy.HTTPError('500 Internal Server Error', str(errmsg))

  @cherrypy.expose
  def controlfiles(self, **params):
    """Return a control file or a list of all known control files.

    Example URL:
      To List all control files:
      http://dev-server/controlfiles?board=x86-alex-release&build=R18-1514.0.0
      To return the contents of a path:
      http://dev-server/controlfiles?board=x86-alex-release&build=R18-1514.0.0&control_path=client/sleeptest/control

    Args:
      build: The build i.e. x86-alex-release/R18-1514.0.0-a1-b1450.
      control_path: If you want the contents of a control file set this
        to the path. E.g. client/site_tests/sleeptest/control
        Optional, if not provided return a list of control files is returned.
    Returns:
      Contents of a control file if control_path is provided.
      A list of control files if no control_path is provided.
    """
    if not params:
      return _PrintDocStringAsHTML(self.controlfiles)

    if 'build' not in params:
      raise cherrypy.HTTPError('500 Internal Server Error',
                               'Error: build= is required!')

    if 'control_path' not in params:
      return common_util.GetControlFileList(
          updater.static_dir, params['build'])
    else:
      return common_util.GetControlFile(
          updater.static_dir, params['build'], params['control_path'])

  @cherrypy.expose
  def stage_images(self, **kwargs):
    """Downloads and stages a Chrome OS image from Google Storage.

    THIS METHOD IS DEPRECATED: use stage(..., artifacts=...) instead.
    This method downloads a zipped archive from a specified GS location, then
    extracts and stages the specified list of images and stages them under
    static/BOARD/BUILD/. Download is synchronous.

    Args:
      archive_url: Google Storage URL for the build.
      image_types: comma-separated list of images to download, may include
                   'test', 'recovery', and 'base'

    Example URL:
      http://myhost/stage_images?archive_url=gs://chromeos-image-archive/
      x86-generic/R17-1208.0.0-a1-b338&image_types=test,base
    """
    image_types = kwargs.get('image_types').split(',')
    image_types_list = [image + '_image' for image in image_types]
    self.stage(archive_url=kwargs.get('archive_url'), artifacts=','.join(
        image_types_list))

  @cherrypy.expose
  def xbuddy(self, *args, **kwargs):
    """The full xBuddy call, returns resource specified by path_parts.

    Args:
      path_parts: the path following xbuddy/ in the call url is split into the
        components of the path.
        The path can be understood as a build_id/artifact, build_id is
        composed of "board/version"

        path_parts[0], the board, is the familiar board name, optionally
          suffixed.
        path_parts[1], the version, can be the google storage version
          number, and may also be any of a number of xBuddy defined version
          aliases that will be translated into the latest built image that
          fits the description. defaults to latest.
        path_parts[2], the artifact, is one of a number of image or artifact
          aliases used by xbuddy, defined in xbuddy:ALIASES. Defaults to test

    Kwargs:
      return_dir: {true|false}
                  if set to true, returns the url to the update.gz
                  instead.

    Example URL:
      http://host:port/xbuddy/x86-generic/R26-4000.0.0/test
      or
      http://host:port/xbuddy/x86-generic/R26-4000.0.0/test?return_dir=true

    Returns:
      A redirect to the image or update file on the devserver.
      e.g. http://host:port/static/archive/x86-generic-release/
      R26-4000.0.0/chromium-test-image.bin
      or if return_dir is True, return path to the folder where
      image or update file is
      http://host:port/static/x86-generic-release/R26-4000.0.0/
    """
    boolean_string = kwargs.get('return_dir')
    return_dir = xbuddy.XBuddy.ParseBoolean(boolean_string)
    return_url = self._xbuddy.Get(args,
                                  return_dir)
    if return_dir:
      directory = os.path.join(cherrypy.request.base, return_url)
      _Log("Directory requested, returning: %s", directory)
      return directory
    else:
      return_url = '/' + return_url
      _Log("Payload requested, returning: %s", return_url)
      raise cherrypy.HTTPRedirect(return_url, 302)

  @cherrypy.expose
  def xbuddy_list(self):
    """Lists the currently available images & time since last access.

    @return: A string representation of a list of tuples
      [(build_id, time since last access),...]
    """
    return self._xbuddy.List()

  @cherrypy.expose
  def xbuddy_capacity(self):
    """Returns the number of images cached by xBuddy.

    @return: Capacity of this devserver.
    """
    return self._xbuddy.Capacity()

  @cherrypy.expose
  def index(self):
    """Presents a welcome message and documentation links."""
    return ('Welcome to the Dev Server!<br>\n'
            '<br>\n'
            'Here are the available methods, click for documentation:<br>\n'
            '<br>\n'
            '%s' %
            '<br>\n'.join(
                [('<a href=doc/%s>%s</a>' % (name, name))
                 for name in _FindExposedMethods(
                     self, '', unlisted=self._UNLISTED_METHODS)]))

  @cherrypy.expose
  def doc(self, *args):
    """Shows the documentation for available methods / URLs.

    Example:
      http://myhost/doc/update
    """
    name = '/'.join(args)
    method = _GetExposedMethod(self, name)
    if not method:
      raise DevServerError("No exposed method named `%s'" % name)
    if not method.__doc__:
      raise DevServerError("No documentation for exposed method `%s'" % name)
    return '<pre>\n%s</pre>' % method.__doc__

  @cherrypy.expose
  def update(self, *args):
    """Handles an update check from a Chrome OS client.

    The HTTP request should contain the standard Omaha-style XML blob. The URL
    line may contain an additional intermediate path to the update payload.

    Example:
      http://myhost/update/optional/path/to/payload
    """
    label = '/'.join(args)
    body_length = int(cherrypy.request.headers.get('Content-Length', 0))
    data = cherrypy.request.rfile.read(body_length)
    return updater.HandleUpdatePing(data, label)


  @cherrypy.expose
  def check_health(self):
    """Collect the health status of devserver to see if it's ready for staging.

    @return: A JSON dictionary containing all or some of the following fields:
        free_disk (int):            free disk space in GB
        staging_thread_count (int): number of devserver threads currently
            staging an image
    """
    # Get free disk space.
    stat = os.statvfs(updater.static_dir)
    free_disk = stat.f_bsize * stat.f_bavail / 1000000000

    return json.dumps({
        'free_disk': free_disk,
        'staging_thread_count': DevServerRoot._staging_thread_count,
    })


def _CleanCache(cache_dir, wipe):
  """Wipes any excess cached items in the cache_dir.

  Args:
    cache_dir: the directory we are wiping from.
    wipe: If True, wipe all the contents -- not just the excess.
  """
  if wipe:
    # Clear the cache and exit on error.
    cmd = 'rm -rf %s/*' % cache_dir
    if os.system(cmd) != 0:
      _Log('Failed to clear the cache with %s' % cmd)
      sys.exit(1)
  else:
    # Clear all but the last N cached updates
    cmd = ('cd %s; ls -tr | head --lines=-%d | xargs rm -rf' %
           (cache_dir, CACHED_ENTRIES))
    if os.system(cmd) != 0:
      _Log('Failed to clean up old delta cache files with %s' % cmd)
      sys.exit(1)


def _AddTestingOptions(parser):
  group = optparse.OptionGroup(
      parser, 'Advanced Testing Options', 'These are used by test scripts and '
      'developers writing integration tests utilizing the devserver. They are '
      'not intended to be really used outside the scope of someone '
      'knowledgable about the test.')
  group.add_option('--exit',
                   action='store_true',
                   help='do not start the server (yet pregenerate/clear cache)')
  group.add_option('--host_log',
                   action='store_true', default=False,
                   help='record history of host update events (/api/hostlog)')
  group.add_option('--max_updates',
                   metavar='NUM', default= -1, type='int',
                   help='maximum number of update checks handled positively '
                        '(default: unlimited)')
  group.add_option('--private_key',
                   metavar='PATH', default=None,
                   help='path to the private key in pem format. If this is set '
                   'the devserver will generate update payloads that are '
                   'signed with this key.')
  group.add_option('--proxy_port',
                   metavar='PORT', default=None, type='int',
                   help='port to have the client connect to -- basically the '
                   'devserver lies to the update to tell it to get the payload '
                   'from a different port that will proxy the request back to '
                   'the devserver. The proxy must be managed outside the '
                   'devserver.')
  group.add_option('--remote_payload',
                   action='store_true', default=False,
                   help='Payload is being served from a remote machine')
  group.add_option('-u', '--urlbase',
                   metavar='URL',
                     help='base URL for update images, other than the '
                     'devserver. Use in conjunction with remote_payload.')
  parser.add_option_group(group)


def _AddUpdateOptions(parser):
  group = optparse.OptionGroup(
      parser, 'Autoupdate Options', 'These options can be used to change '
      'how the devserver either generates or serve update payloads. Please '
      'note that all of these option affect how a payload is generated and so '
      'do not work in archive-only mode.')
  group.add_option('--board',
                   help='By default the devserver will create an update '
                   'payload from the latest image built for the board '
                   'a device that is requesting an update has. When we '
                   'pre-generate an update (see below) and we do not specify '
                   'another update_type option like image or payload, the '
                   'devserver needs to know the board to generate the latest '
                   'image for. This is that board.')
  group.add_option('--critical_update',
                   action='store_true', default=False,
                   help='Present update payload as critical')
  group.add_option('--for_vm',
                   dest='vm', action='store_true',
                   help='DEPRECATED: see no_patch_kernel.')
  group.add_option('--image',
                   metavar='FILE',
                   help='Generate and serve an update using this image to any '
                   'device that requests an update.')
  group.add_option('--no_patch_kernel',
                   dest='patch_kernel', action='store_false', default=True,
                   help='When generating an update payload, do not patch the '
                   'kernel with kernel verification blob from the stateful '
                   'partition.')
  group.add_option('--payload',
                   metavar='PATH',
                   help='use the update payload from specified directory '
                   '(update.gz).')
  group.add_option('-p', '--pregenerate_update',
                   action='store_true', default=False,
                   help='pre-generate the update payload before accepting '
                   'update requests. Useful to help debug payload generation '
                   'issues quickly. Also if an update payload will take a '
                   'long time to generate, a client may timeout if you do not'
                   'pregenerate the update.')
  group.add_option('--src_image',
                   metavar='PATH', default='',
                   help='If specified, delta updates will be generated using '
                   'this image as the source image. Delta updates are when '
                   'you are updating from a "source image" to a another '
                   'image.')
  parser.add_option_group(group)


def _AddProductionOptions(parser):
  group = optparse.OptionGroup(
      parser, 'Advanced Server Options', 'These options can be used to changed '
      'for advanced server behavior.')
  # TODO(sosa): Clean up the fact we have archive_dir and data_dir. It's ugly.
  # Should be --archive_mode + optional data_dir.
  group.add_option('--archive_dir',
                   metavar='PATH',
                   help='Enables archive-only mode. This disables any '
                   'update or package generation related functionality. This '
                   'mode also works without a Chromium OS chroot.')
  group.add_option('--clear_cache',
                   action='store_true', default=False,
                   help='At startup, removes all cached entries from the'
                   'devserver\'s cache.')
  group.add_option('--logfile',
                   metavar='PATH',
                   help='log output to this file instead of stdout')
  group.add_option('--production',
                   action='store_true', default=False,
                   help='have the devserver use production values when '
                   'starting up. This includes using more threads and '
                   'performing less logging.')
  parser.add_option_group(group)


def _MakeLogHandler(logfile):
  """Create a LogHandler instance used to log all messages."""
  hdlr_cls = handlers.TimedRotatingFileHandler
  hdlr = hdlr_cls(logfile, when=_LOG_ROTATION_TIME,
                  backupCount=_LOG_ROTATION_BACKUP)
  # The cherrypy documentation says to use the _cplogging module for
  # this, even though it's named as a private module.
  # pylint: disable=W0212
  hdlr.setFormatter(cherrypy._cplogging.logfmt)
  return hdlr


def main():
  usage = '\n\n'.join(['usage: %prog [options]', __doc__])
  parser = optparse.OptionParser(usage=usage)
  parser.add_option('--data_dir',
                    metavar='PATH',
                    default=os.path.dirname(os.path.abspath(sys.argv[0])),
                    help='writable directory where static lives')
  parser.add_option('--port',
                    default=8080, type='int',
                    help='port for the dev server to use (default: 8080)')
  parser.add_option('-t', '--test_image',
                    action='store_true',
                    help='If set, look for the chromiumos_test_image.bin file '
                    'when generating update payloads rather than the '
                    'chromiumos_image.bin which is the default.')
  _AddProductionOptions(parser)
  _AddUpdateOptions(parser)
  _AddTestingOptions(parser)
  (options, _) = parser.parse_args()

  # Handle options that must be set globally in cherrypy.  Do this
  # work up front, because calls to _Log() below depend on this
  # initialization.
  if options.production:
    cherrypy.config.update({'environment': 'production'})
  if not options.logfile:
    cherrypy.config.update({'log.screen': True})
  else:
    cherrypy.config.update({'log.error_file': '',
                            'log.access_file': ''})
    hdlr = _MakeLogHandler(options.logfile)
    # Pylint can't seem to process these two calls properly
    # pylint: disable=E1101
    cherrypy.log.access_log.addHandler(hdlr)
    cherrypy.log.error_log.addHandler(hdlr)
    # pylint: enable=E1101

  devserver_dir = os.path.dirname(os.path.abspath(sys.argv[0]))
  root_dir = os.path.realpath('%s/../..' % devserver_dir)
  serve_only = False

  static_dir = os.path.realpath('%s/static' % options.data_dir)
  os.system('mkdir -p %s' % static_dir)

  # TODO(sosa): Remove after deprecation.
  if options.vm:
    options.patch_kernel = False

  if options.archive_dir:
    # TODO(zbehan) Remove legacy support:
    #  archive_dir is the directory where static/archive will point.
    #  If this is an absolute path, all is fine. If someone calls this
    #  using a relative path, that is relative to src/platform/dev/.
    #  That use case is unmaintainable, but since applications use it
    #  with =./static, instead of a boolean flag, we'll make this
    #  relative to devserver_dir  to keep these unbroken. For now.
    archive_dir = options.archive_dir
    if not os.path.isabs(archive_dir):
      archive_dir = os.path.realpath(os.path.join(devserver_dir, archive_dir))
    _PrepareToServeUpdatesOnly(archive_dir, static_dir)
    static_dir = os.path.realpath(archive_dir)
    serve_only = True

  cache_dir = os.path.join(static_dir, 'cache')
  # If our devserver is only supposed to serve payloads, we shouldn't be
  # mucking with the cache at all. If the devserver hadn't previously
  # generated a cache and is expected, the caller is using it wrong.
  if serve_only:
    # Extra check to make sure we're not being called incorrectly.
    if (options.clear_cache or options.exit or options.pregenerate_update or
        options.board or options.image):
      parser.error('Incompatible flags detected for serve_only mode.')
  elif os.path.exists(cache_dir):
    _CleanCache(cache_dir, options.clear_cache)
  else:
    os.makedirs(cache_dir)

  _Log('Using cache directory %s' % cache_dir)
  _Log('Data dir is %s' % options.data_dir)
  _Log('Source root is %s' % root_dir)
  _Log('Serving from %s' % static_dir)

  # We allow global use here to share with cherrypy classes.
  # pylint: disable=W0603
  global updater
  updater = autoupdate.Autoupdate(
      root_dir=root_dir,
      static_dir=static_dir,
      serve_only=serve_only,
      urlbase=options.urlbase,
      test_image=options.test_image,
      forced_image=options.image,
      payload_path=options.payload,
      proxy_port=options.proxy_port,
      src_image=options.src_image,
      patch_kernel=options.patch_kernel,
      board=options.board,
      copy_to_static_root=not options.exit,
      private_key=options.private_key,
      critical_update=options.critical_update,
      remote_payload=options.remote_payload,
      max_updates=options.max_updates,
      host_log=options.host_log,
  )

  if options.pregenerate_update:
    updater.PreGenerateUpdate()

  if options.exit:
    return

  _xbuddy = xbuddy.XBuddy(static_dir)
  dev_server = DevServerRoot(_xbuddy)

  cherrypy.quickstart(dev_server, config=_GetConfig(options))


if __name__ == '__main__':
  main()