text: # coding: utf-8
  """A tornado based Jupyter server."""
  
  
  # This code is heaavily based on code from jupyter_server, copied under the
  # following license:
  #
  # This project is licensed under the terms of the Modified BSD License
  # (also known as New or Revised or 3-Clause BSD), as follows:
  #
  # - Copyright (c) 2001-2015, IPython Development Team
  # - Copyright (c) 2015-, Jupyter Development Team
  #
  # All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions are met:
  #
  # Redistributions of source code must retain the above copyright notice, this
  # list of conditions and the following disclaimer.
  #
  # Redistributions in binary form must reproduce the above copyright notice, this
  # list of conditions and the following disclaimer in the documentation and/or
  # other materials provided with the distribution.
  #
  # Neither the name of the Jupyter Development Team nor the names of its
  # contributors may be used to endorse or promote products derived from this
  # software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  # DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
  # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  
  from __future__ import absolute_import, print_function
  
  import binascii
  import datetime
  import errno
  import gettext
  import hashlib
  import hmac
  import importlib
  import io
  import ipaddress
  import json
  import logging
  import mimetypes
  import os
  import random
  import re
  import select
  import signal
  import socket
  import sys
  import threading
  import time
  import warnings
  import webbrowser
  
  # Workaround while lab code imports notebook code
  # TODO: Remove once lab uses jupyter_server
  import jupyter_server.prometheus.metrics
  import jupyter_server.prometheus.log_functions
  try:
      import notebook.prometheus
      import notebook.prometheus.metrics
      import notebook.prometheus.log_functions
  except ImportError:
      sys.modules['notebook.metrics'] = sys.modules['jupyter_server.prometheus.metrics']
      sys.modules['notebook.metrics'].update(sys.modules['jupyter_server.prometheus.log_functions'])
  except ValueError:
      sys.modules['notebook.prometheus.metrics'] = sys.modules['jupyter_server.prometheus.metrics']
      sys.modules['notebook.prometheus.log_functions'] = sys.modules['jupyter_server.prometheus.log_functions']
  
  
  try:  # PY3
      from base64 import encodebytes
  except ImportError:  # PY2
      from base64 import encodestring as encodebytes
  
  
  from jinja2 import Environment, FileSystemLoader
  
  from jupyter_server.transutils import trans, _
  
  # Install the pyzmq ioloop. This has to be done before anything else from
  # tornado is imported.
  from zmq.eventloop import ioloop
  
  ioloop.install()
  
  # check for tornado 3.1.0
  try:
      import tornado
  except ImportError:
      raise ImportError(_("The Jupyter Server requires tornado >= 4.0"))
  try:
      version_info = tornado.version_info
  except AttributeError:
      raise ImportError(
          _("The Jupyter Server requires tornado >= 4.0, but you have < 1.1.0")
      )
  if version_info < (4, 0):
      raise ImportError(
          _("The Jupyter Server requires tornado >= 4.0, but you have %s")
          % tornado.version
      )
  
  from tornado import httpserver
  from tornado import web
  from tornado.httputil import url_concat
  from tornado.log import LogFormatter, app_log, access_log, gen_log
  
  from jupyter_server import (
      DEFAULT_STATIC_FILES_PATH,
      DEFAULT_TEMPLATE_PATH_LIST,
      __version__,
  )
  
  # py23 compatibility
  try:
      raw_input = raw_input
  except NameError:
      raw_input = input
  
  from jupyter_server.base.handlers import RedirectWithParams, Template404
  from jupyter_server.log import log_request
  from jupyter_server.services.kernels.kernelmanager import MappingKernelManager
  from jupyter_server.services.config import ConfigManager
  from jupyter_server.services.contents.manager import ContentsManager
  from jupyter_server.services.contents.filemanager import FileContentsManager
  from jupyter_server.services.contents.largefilemanager import LargeFileManager
  from jupyter_server.services.sessions.sessionmanager import SessionManager
  
  from jupyter_server.auth.login import LoginHandler
  from jupyter_server.auth.logout import LogoutHandler
  from jupyter_server.base.handlers import FileFindHandler
  
  from traitlets.config import Config
  from traitlets.config.application import catch_config_error, boolean_flag
  from jupyter_core.application import JupyterApp, base_flags, base_aliases
  from jupyter_core.paths import jupyter_config_path
  from jupyter_client import KernelManager
  from jupyter_client.kernelspec import (
      KernelSpecManager,
      NoSuchKernel,
      NATIVE_KERNEL_NAME,
  )
  from jupyter_client.session import Session
  from nbformat.sign import NotebookNotary
  from traitlets import (
      Any,
      Dict,
      Unicode,
      Integer,
      List,
      Bool,
      Bytes,
      Instance,
      TraitError,
      Type,
      Float,
      observe,
      default,
      validate,
  )
  from ipython_genutils import py3compat
  from jupyter_core.paths import jupyter_runtime_dir, jupyter_path
  from jupyter_server._sysinfo import get_sys_info
  
  from jupyter_server._tz import utcnow, utcfromtimestamp
  from jupyter_server.utils import url_path_join, check_pid, url_escape
  
  # -----------------------------------------------------------------------------
  # Module globals
  # -----------------------------------------------------------------------------
  
  _examples = """
  jupyter server                       # start the server
  jupyter server  --certfile=mycert.pem # use SSL/TLS certificate
  jupyter server password              # enter a password to protect the server
  """
  
  # -----------------------------------------------------------------------------
  # Helper functions
  # -----------------------------------------------------------------------------
  
  
  def random_ports(port, n):
      """Generate a list of n random ports near the given port.
  
      The first 5 ports will be sequential, and the remaining n-5 will be
      randomly selected in the range [port-2*n, port+2*n].
      """
      for i in range(min(5, n)):
          yield port + i
      for i in range(n - 5):
          yield max(1, port + random.randint(-2 * n, 2 * n))
  
  
  def load_handlers(name):
      """Load the (URL pattern, handler) tuples for each component."""
      mod = __import__(name, fromlist=["default_handlers"])
      return mod.default_handlers
  
  
  # -----------------------------------------------------------------------------
  # The Tornado web application
  # -----------------------------------------------------------------------------
  
  
  class ServerWebApplication(web.Application):
      def __init__(
          self,
          jupyter_app,
          kernel_manager,
          contents_manager,
          session_manager,
          kernel_spec_manager,
          config_manager,
          extra_services,
          default_services,
          log,
          base_url,
          default_url,
          settings_overrides,
          jinja_env_options,
      ):
  
          settings = self.init_settings(
              jupyter_app,
              kernel_manager,
              contents_manager,
              session_manager,
              kernel_spec_manager,
              config_manager,
              extra_services,
              default_services,
              log,
              base_url,
              default_url,
              settings_overrides,
              jinja_env_options,
          )
          handlers = self.init_handlers(settings)
  
          super(ServerWebApplication, self).__init__(handlers, **settings)
  
      def init_settings(
          self,
          jupyter_app,
          kernel_manager,
          contents_manager,
          session_manager,
          kernel_spec_manager,
          config_manager,
          extra_services,
          default_services,
          log,
          base_url,
          default_url,
          settings_overrides,
          jinja_env_options=None,
      ):
  
          _template_path = settings_overrides.get(
              "template_path", jupyter_app.template_file_path
          )
          if isinstance(_template_path, py3compat.string_types):
              _template_path = (_template_path,)
          template_path = [os.path.expanduser(path) for path in _template_path]
  
          jenv_opt = {"autoescape": True}
          jenv_opt.update(jinja_env_options if jinja_env_options else {})
  
          env = Environment(
              loader=FileSystemLoader(template_path),
              extensions=["jinja2.ext.i18n"],
              **jenv_opt
          )
          sys_info = get_sys_info()
  
          # If the user is running the server in a git directory, make the assumption
          # that this is a dev install and suggest to the developer `npm run build:watch`.
          base_dir = os.path.realpath(os.path.join(__file__, "..", ".."))
  
          nbui = gettext.translation(
              "nbui",
              localedir=os.path.join(base_dir, "jupyter_server/i18n"),
              fallback=True,
          )
          env.install_gettext_translations(nbui, newstyle=False)
  
          if sys_info["commit_source"] == "repository":
              # don't cache (rely on 304) when working from master
              version_hash = ""
          else:
              # reset the cache on server restart
              version_hash = datetime.datetime.now().strftime("%Y%m%d%H%M%S")
  
          now = utcnow()
  
          root_dir = contents_manager.root_dir
          home = os.path.expanduser("~")
          if root_dir.startswith(home + os.path.sep):
              # collapse $HOME to ~
              root_dir = "~" + root_dir[len(home) :]
  
          settings = dict(
              # basics
              log_function=log_request,
              base_url=base_url,
              default_url=default_url,
              template_path=template_path,
              static_path=jupyter_app.static_file_path,
              static_custom_path=jupyter_app.static_custom_path,
              static_handler_class=FileFindHandler,
              static_url_prefix=url_path_join(base_url, "/static/"),
              static_handler_args={
                  # don't cache custom.js
                  "no_cache_paths": [url_path_join(base_url, "static", "custom")]
              },
              version_hash=version_hash,
              # rate limits
              iopub_msg_rate_limit=jupyter_app.iopub_msg_rate_limit,
              iopub_data_rate_limit=jupyter_app.iopub_data_rate_limit,
              rate_limit_window=jupyter_app.rate_limit_window,
              # maximum request sizes - support saving larger notebooks
              # tornado defaults are 100 MiB, we increase it to 0.5 GiB
              max_body_size=512 * 1024 * 1024,
              max_buffer_size=512 * 1024 * 1024,
              # authentication
              cookie_secret=jupyter_app.cookie_secret,
              login_url=url_path_join(base_url, "/login"),
              login_handler_class=jupyter_app.login_handler_class,
              logout_handler_class=jupyter_app.logout_handler_class,
              password=jupyter_app.password,
              xsrf_cookies=True,
              disable_check_xsrf=jupyter_app.disable_check_xsrf,
              allow_remote_access=jupyter_app.allow_remote_access,
              local_hostnames=jupyter_app.local_hostnames,
              # managers
              kernel_manager=kernel_manager,
              contents_manager=contents_manager,
              session_manager=session_manager,
              kernel_spec_manager=kernel_spec_manager,
              config_manager=config_manager,
              # handlers
              extra_services=extra_services,
              default_services=default_services,
              # Jupyter stuff
              started=now,
              # place for extensions to register activity
              # so that they can prevent idle-shutdown
              last_activity_times={},
              jinja_template_vars=jupyter_app.jinja_template_vars,
              websocket_url=jupyter_app.websocket_url,
              shutdown_button=jupyter_app.quit_button,
              config=jupyter_app.config,
              config_dir=jupyter_app.config_dir,
              allow_password_change=jupyter_app.allow_password_change,
              server_root_dir=root_dir,
              jinja2_env=env,
              terminals_available=False,  # Set later if terminals are available
          )
  
          # allow custom overrides for the tornado web app.
          settings.update(settings_overrides)
          return settings
  
      def init_handlers(self, settings):
          """Load the (URL pattern, handler) tuples for each component."""
  
          # Order matters. The first handler to match the URL will handle the request.
          handlers = []
          # load extra services specified by users before default handlers
          for service in settings["extra_services"]:
              handlers.extend(load_handlers(service))
          handlers.extend([(r"/login", settings["login_handler_class"])])
          handlers.extend([(r"/logout", settings["logout_handler_class"])])
          for service in settings["default_services"]:
              handlers.extend(load_handlers(service))
          handlers.extend(settings["contents_manager"].get_extra_handlers())
  
          handlers.append(
              (
                  r"/custom/(.*)",
                  FileFindHandler,
                  {
                      "path": settings["static_custom_path"],
                      "no_cache_paths": ["/"],  # don't cache anything in custom
                  },
              )
          )
          # register base handlers last
          handlers.extend(load_handlers("jupyter_server.base.handlers"))
  
          if settings["default_url"] not in ("/", settings["base_url"]):
              # set the URL that will be redirected from `/`
              handlers.append(
                  (
                      r"/?",
                      RedirectWithParams,
                      {
                          "url": settings["default_url"],
                          "permanent": False,  # want 302, not 301
                      },
                  )
              )
  
          # prepend base_url onto the patterns that we match
          new_handlers = []
          for handler in handlers:
              pattern = url_path_join(settings["base_url"], handler[0])
              new_handler = tuple([pattern] + list(handler[1:]))
              new_handlers.append(new_handler)
          # add 404 on the end, which will catch everything that falls through
          new_handlers.append((r"(.*)", Template404))
          return new_handlers
  
      def last_activity(self):
          """Get a UTC timestamp for when the server last did something.
  
          Includes: API activity, kernel activity, kernel shutdown, and terminal
          activity.
          """
          sources = [
              self.settings["started"],
              self.settings["kernel_manager"].last_kernel_activity,
          ]
          try:
              sources.append(self.settings["api_last_activity"])
          except KeyError:
              pass
          try:
              sources.append(self.settings["terminal_last_activity"])
          except KeyError:
              pass
          sources.extend(self.settings["last_activity_times"].values())
          return max(sources)
  
  
  class JupyterPasswordApp(JupyterApp):
      """Set a password for the Jupyter server.
  
      Setting a password secures the Jupyter server
      and removes the need for token-based authentication.
      """
  
      description = __doc__
  
      def _config_file_default(self):
          return os.path.join(self.config_dir, "jupyter_server_config.json")
  
      def start(self):
          from jupyter_server.auth.security import set_password
  
          set_password(config_file=self.config_file)
          self.log.info("Wrote hashed password to %s" % self.config_file)
  
  
  def shutdown_server(server_info, timeout=5, log=None):
      """Shutdown a notebook server in a separate process.
  
      *server_info* should be a dictionary as produced by list_running_servers().
  
      Will first try to request shutdown using /api/shutdown .
      On Unix, if the server is still running after *timeout* seconds, it will
      send SIGTERM. After another timeout, it escalates to SIGKILL.
  
      Returns True if the server was stopped by any means, False if stopping it
      failed (on Windows).
      """
      from tornado.httpclient import HTTPClient, HTTPRequest
  
      url = server_info["url"]
      pid = server_info["pid"]
      req = HTTPRequest(
          url + "api/shutdown",
          method="POST",
          body=b"",
          headers={"Authorization": "token " + server_info["token"]},
      )
      if log:
          log.debug("POST request to %sapi/shutdown", url)
      HTTPClient().fetch(req)
  
      # Poll to see if it shut down.
      for _ in range(timeout * 10):
          if check_pid(pid):
              if log:
                  log.debug("Server PID %s is gone", pid)
              return True
          time.sleep(0.1)
  
      if sys.platform.startswith("win"):
          return False
  
      if log:
          log.debug("SIGTERM to PID %s", pid)
      os.kill(pid, signal.SIGTERM)
  
      # Poll to see if it shut down.
      for _ in range(timeout * 10):
          if check_pid(pid):
              if log:
                  log.debug("Server PID %s is gone", pid)
              return True
          time.sleep(0.1)
  
      if log:
          log.debug("SIGKILL to PID %s", pid)
      os.kill(pid, signal.SIGKILL)
      return True  # SIGKILL cannot be caught
  
  
  class JupyterServerStopApp(JupyterApp):
  
      version = __version__
      description = "Stop currently running Jupyter server for a given port"
  
      port = Integer(
          8888, config=True, help="Port of the server to be killed. Default 8888"
      )
  
      def parse_command_line(self, argv=None):
          super(JupyterServerStopApp, self).parse_command_line(argv)
          if self.extra_args:
              self.port = int(self.extra_args[0])
  
      def shutdown_server(self, server):
          return shutdown_server(server, log=self.log)
  
      def start(self):
          servers = list(list_running_servers(self.runtime_dir))
          if not servers:
              self.exit("There are no running servers")
          for server in servers:
              if server["port"] == self.port:
                  print("Shutting down server on port", self.port, "...")
                  if not self.shutdown_server(server):
                      sys.exit("Could not stop server")
                  return
          else:
              print(
                  "There is currently no server running on port {}".format(self.port),
                  file=sys.stderr,
              )
              print("Ports currently in use:", file=sys.stderr)
              for server in servers:
                  print("  - {}".format(server["port"]), file=sys.stderr)
              self.exit(1)
  
  
  class JupyterServerListApp(JupyterApp):
      version = __version__
      description = _("List currently running notebook servers.")
  
      flags = dict(
          jsonlist=(
              {"JupyterServerListApp": {"jsonlist": True}},
              _("Produce machine-readable JSON list output."),
          ),
          json=(
              {"JupyterServerListApp": {"json": True}},
              _("Produce machine-readable JSON object on each line of output."),
          ),
      )
  
      jsonlist = Bool(
          False,
          config=True,
          help=_(
              "If True, the output will be a JSON list of objects, one per "
              "active notebook server, each with the details from the "
              "relevant server info file."
          ),
      )
      json = Bool(
          False,
          config=True,
          help=_(
              "If True, each line of output will be a JSON object with the "
              "details from the server info file. For a JSON list output, "
              "see the JupyterServerListApp.jsonlist configuration value"
          ),
      )
  
      def start(self):
          serverinfo_list = list(list_running_servers(self.runtime_dir))
          if self.jsonlist:
              print(json.dumps(serverinfo_list, indent=2))
          elif self.json:
              for serverinfo in serverinfo_list:
                  print(json.dumps(serverinfo))
          else:
              print("Currently running servers:")
              for serverinfo in serverinfo_list:
                  url = serverinfo["url"]
                  if serverinfo.get("token"):
                      url = url + "?token=%s" % serverinfo["token"]
                  print(url, "::", serverinfo["root_dir"])
  
  
  # -----------------------------------------------------------------------------
  # Aliases and Flags
  # -----------------------------------------------------------------------------
  
  flags = dict(base_flags)
  
  flags["allow-root"] = (
      {"ServerApp": {"allow_root": True}},
      _("Allow the server to be run from root user."),
  )
  flags["no-browser"] = (
      {"ServerApp": {"open_browser": False}},
      _("Prevent the opening of the default url in the browser."),
  )
  
  # Add notebook manager flags
  flags.update(
      boolean_flag(
          "script",
          "FileContentsManager.save_script",
          "DEPRECATED, IGNORED",
          "DEPRECATED, IGNORED",
      )
  )
  
  aliases = dict(base_aliases)
  
  aliases.update(
      {
          "ip": "ServerApp.ip",
          "port": "ServerApp.port",
          "port-retries": "ServerApp.port_retries",
          "transport": "KernelManager.transport",
          "keyfile": "ServerApp.keyfile",
          "certfile": "ServerApp.certfile",
          "client-ca": "ServerApp.client_ca",
          "notebook-dir": "ServerApp.root_dir",
          "browser": "ServerApp.browser",
          "pylab": "ServerApp.pylab",
      }
  )
  
  # -----------------------------------------------------------------------------
  # ServerApp
  # -----------------------------------------------------------------------------
  
  
  class ServerApp(JupyterApp):
  
      name = "jupyter-server"
      version = __version__
      description = _(
          """The Jupyter Server.
  
      This launches a Tornado-based Jupyter Server."""
      )
      examples = _examples
      aliases = aliases
      flags = flags
  
      classes = [
          KernelManager,
          Session,
          MappingKernelManager,
          ContentsManager,
          FileContentsManager,
          NotebookNotary,
          KernelSpecManager,
      ]
      flags = Dict(flags)
      aliases = Dict(aliases)
  
      subcommands = dict(
          list=(JupyterServerListApp, JupyterServerListApp.description.splitlines()[0]),
          stop=(JupyterServerStopApp, JupyterServerStopApp.description.splitlines()[0]),
          password=(JupyterPasswordApp, JupyterPasswordApp.description.splitlines()[0]),
      )
  
      _log_formatter_cls = LogFormatter
  
      @default("log_level")
      def _default_log_level(self):
          return logging.INFO
  
      @default("log_datefmt")
      def _default_log_datefmt(self):
          """Exclude date from default date format"""
          return "%H:%M:%S"
  
      @default("log_format")
      def _default_log_format(self):
          """override default log format to include time"""
          return u"%(color)s[%(levelname)1.1s %(asctime)s.%(msecs).03d %(name)s]%(end_color)s %(message)s"
  
      file_to_run = Unicode(
          "", config=True,
          help='file to be opened in the Jupyter server')
  
      file_to_run_url = Unicode(
          "", config=True,
          help='url prefix to use for file_to_run')
  
      # Network related information
  
      allow_origin = Unicode(
          "",
          config=True,
          help="""Set the Access-Control-Allow-Origin header
  
          Use '*' to allow any origin to access your server.
  
          Takes precedence over allow_origin_pat.
          """,
      )
  
      allow_origin_pat = Unicode(
          "",
          config=True,
          help="""Use a regular expression for the Access-Control-Allow-Origin header
  
          Requests from an origin matching the expression will get replies with:
  
              Access-Control-Allow-Origin: origin
  
          where `origin` is the origin of the request.
  
          Ignored if allow_origin is set.
          """,
      )
  
      allow_credentials = Bool(
          False,
          config=True,
          help=_("Set the Access-Control-Allow-Credentials: true header"),
      )
  
      allow_root = Bool(
          False,
          config=True,
          help=_("Whether to allow the user to run the server as root."),
      )
  
      default_url = Unicode(
          "/", config=True, help=_("The default URL to redirect to from `/`")
      )
  
      ip = Unicode(
          "localhost",
          config=True,
          help=_("The IP address the Jupyter server will listen on."),
      )
  
      @default("ip")
      def _default_ip(self):
          """Return localhost if available, 127.0.0.1 otherwise.
  
          On some (horribly broken) systems, localhost cannot be bound.
          """
          s = socket.socket()
          try:
              s.bind(("localhost", 0))
          except socket.error as e:
              self.log.warning(
                  _("Cannot bind to localhost, using 127.0.0.1 as default ip\n%s"), e
              )
              return "127.0.0.1"
          else:
              s.close()
              return "localhost"
  
      @validate("ip")
      def _valdate_ip(self, proposal):
          value = proposal["value"]
          if value == u"*":
              value = u""
          return value
  
      custom_display_url = Unicode(
          u"",
          config=True,
          help=_(
              """Override URL shown to users.
  
          Replace actual URL, including protocol, address, port and base URL,
          with the given value when displaying URL to the users. Do not change
          the actual connection URL. If authentication token is enabled, the
          token is added to the custom URL automatically.
  
          This option is intended to be used when the URL to display to the user
          cannot be determined reliably by the Jupyter server (proxified
          or containerized setups for example)."""
          ),
      )
  
      port = Integer(
          8888, config=True, help=_("The port the Jupyter server will listen on.")
      )
  
      port_retries = Integer(
          50,
          config=True,
          help=_(
              "The number of additional ports to try if the specified port is not available."
          ),
      )
  
      certfile = Unicode(
          u"", config=True, help=_("""The full path to an SSL/TLS certificate file.""")
      )
  
      keyfile = Unicode(
          u"",
          config=True,
          help=_("""The full path to a private key file for usage with SSL/TLS."""),
      )
  
      client_ca = Unicode(
          u"",
          config=True,
          help=_(
              """The full path to a certificate authority certificate for SSL/TLS client authentication."""
          ),
      )
  
      cookie_secret_file = Unicode(
          config=True, help=_("""The file where the cookie secret is stored.""")
      )
  
      @default("cookie_secret_file")
      def _default_cookie_secret_file(self):
          return os.path.join(self.runtime_dir, "jupytr_cookie_secret")
  
      cookie_secret = Bytes(
          b"",
          config=True,
          help="""The random bytes used to secure cookies.
          By default this is a new random number every time you start the server.
          Set it to a value in a config file to enable logins to persist across server sessions.
  
          Note: Cookie secrets should be kept private, do not share config files with
          cookie_secret stored in plaintext (you can read the value from a file).
          """,
      )
  
      @default("cookie_secret")
      def _default_cookie_secret(self):
          if os.path.exists(self.cookie_secret_file):
              with io.open(self.cookie_secret_file, "rb") as f:
                  key = f.read()
          else:
              key = encodebytes(os.urandom(32))
              self._write_cookie_secret_file(key)
          h = hmac.new(key, digestmod=hashlib.sha256)
          h.update(self.password.encode())
          return h.digest()
  
      def _write_cookie_secret_file(self, secret):
          """write my secret to my secret_file"""
          self.log.info(
              _("Writing notebook server cookie secret to %s"), self.cookie_secret_file
          )
          try:
              with io.open(self.cookie_secret_file, "wb") as f:
                  f.write(secret)
          except OSError as e:
              self.log.error(
                  _("Failed to write cookie secret to %s: %s"), self.cookie_secret_file, e
              )
          try:
              os.chmod(self.cookie_secret_file, 0o600)
          except OSError:
              self.log.warning(
                  _("Could not set permissions on %s"), self.cookie_secret_file
              )
  
      token = Unicode(
          "<generated>",
          help=_(
              """Token used for authenticating first-time connections to the server.
  
          When no password is enabled,
          the default is to generate a new, random token.
  
          Setting to an empty string disables authentication altogether, which is NOT RECOMMENDED.
          """
          ),
      ).tag(config=True)
  
      one_time_token = Unicode(
          help=_(
              """One-time token used for opening a browser.
          Once used, this token cannot be used again.
          """
          )
      )
  
      _token_generated = True
  
      @default("token")
      def _token_default(self):
          if os.getenv("JUPYTER_TOKEN"):
              self._token_generated = False
              return os.getenv("JUPYTER_TOKEN")
          if self.password:
              # no token if password is enabled
              self._token_generated = False
              return u""
          else:
              self._token_generated = True
              return binascii.hexlify(os.urandom(24)).decode("ascii")
  
      @observe("token")
      def _token_changed(self, change):
          self._token_generated = False
  
      password = Unicode(
          u"",
          config=True,
          help="""Hashed password to use for web authentication.
  
                        To generate, type in a python/IPython shell:
  
                          from jupyter_server.auth import passwd; passwd()
  
                        The string should be of the form type:salt:hashed-password.
                        """,
      )
  
      password_required = Bool(
          False,
          config=True,
          help="""Forces users to use a password for the Jupyter server.
                        This is useful in a multi user environment, for instance when
                        everybody in the LAN can access each other's machine through ssh.
  
                        In such a case, serving on localhost is not secure since
                        any user can connect to the Jupyter server via ssh.
  
                        """,
      )
  
      allow_password_change = Bool(
          True,
          config=True,
          help="""Allow password to be changed at login for the Jupyter server.
  
                      While loggin in with a token, the Jupyter server UI will give the opportunity to
                      the user to enter a new password at the same time that will replace
                      the token login mechanism.
  
                      This can be set to false to prevent changing password from the UI/API.
                      """,
      )
  
      disable_check_xsrf = Bool(
          False,
          config=True,
          help="""Disable cross-site-request-forgery protection
  
          Jupyter notebook 4.3.1 introduces protection from cross-site request forgeries,
          requiring API requests to either:
  
          - originate from pages served by this server (validated with XSRF cookie and token), or
          - authenticate with a token
  
          Some anonymous compute resources still desire the ability to run code,
          completely without authentication.
          These services can disable all authentication and security checks,
          with the full knowledge of what that implies.
          """,
      )
  
      allow_remote_access = Bool(
          config=True,
          help="""Allow requests where the Host header doesn't point to a local server
  
         By default, requests get a 403 forbidden response if the 'Host' header
         shows that the browser thinks it's on a non-local domain.
         Setting this option to True disables this check.
  
         This protects against 'DNS rebinding' attacks, where a remote web server
         serves you a page and then changes its DNS to send later requests to a
         local IP, bypassing same-origin checks.
  
         Local IP addresses (such as 127.0.0.1 and ::1) are allowed as local,
         along with hostnames configured in local_hostnames.
         """,
      )
  
      @default("allow_remote_access")
      def _default_allow_remote(self):
          """Disallow remote access if we're listening only on loopback addresses"""
          try:
              addr = ipaddress.ip_address(self.ip)
          except ValueError:
              # Address is a hostname
              for info in socket.getaddrinfo(self.ip, self.port, 0, socket.SOCK_STREAM):
                  addr = info[4][0]
                  if not py3compat.PY3:
                      addr = addr.decode("ascii")
  
                  try:
                      parsed = ipaddress.ip_address(addr.split("%")[0])
                  except ValueError:
                      self.log.warning("Unrecognised IP address: %r", addr)
                      continue
  
                  # Macs map localhost to 'fe80::1%lo0', a link local address
                  # scoped to the loopback interface. For now, we'll assume that
                  # any scoped link-local address is effectively local.
                  if not (parsed.is_loopback or (("%" in addr) and parsed.is_link_local)):
                      return True
              return False
          else:
              return not addr.is_loopback
  
      local_hostnames = List(
          Unicode(),
          ["localhost"],
          config=True,
          help="""Hostnames to allow as local when allow_remote_access is False.
  
         Local IP addresses (such as 127.0.0.1 and ::1) are automatically accepted
         as local as well.
         """,
      )
  
      open_browser = Bool(
          True,
          config=True,
          help="""Whether to open in a browser after starting.
                          The specific browser used is platform dependent and
                          determined by the python standard library `webbrowser`
                          module, unless it is overridden using the --browser
                          (ServerApp.browser) configuration option.
                          """,
      )
  
      browser = Unicode(
          u"",
          config=True,
          help="""Specify what command to use to invoke a web
                        browser when starting the server. If not specified, the
                        default browser will be determined by the `webbrowser`
                        standard library module, which allows setting of the
                        BROWSER environment variable to override it.
                        """,
      )
  
      webbrowser_open_new = Integer(
          2,
          config=True,
          help=_(
              """Specify where to open the server on startup. This is the
          `new` argument passed to the standard library method `webbrowser.open`.
          The behaviour is not guaranteed, but depends on browser support. Valid
          values are:
  
           - 2 opens a new tab,
           - 1 opens a new window,
           - 0 opens in an existing window.
  
          See the `webbrowser.open` documentation for details.
          """
          ),
      )
  
      tornado_settings = Dict(
          config=True,
          help=_(
              "Supply overrides for the tornado.web.Application that the "
              "Jupyter server uses."
          ),
      )
  
      websocket_compression_options = Any(
          None,
          config=True,
          help=_(
              """
          Set the tornado compression options for websocket connections.
  
          This value will be returned from :meth:`WebSocketHandler.get_compression_options`.
          None (default) will disable compression.
          A dict (even an empty one) will enable compression.
  
          See the tornado docs for WebSocketHandler.get_compression_options for details.
          """
          ),
      )
      terminado_settings = Dict(
          config=True,
          help=_(
              'Supply overrides for terminado. Currently only supports "shell_command".'
          ),
      )
  
      cookie_options = Dict(
          config=True,
          help=_(
              "Extra keyword arguments to pass to `set_secure_cookie`."
              " See tornado's set_secure_cookie docs for details."
          ),
      )
      ssl_options = Dict(
          config=True,
          help=_(
              """Supply SSL options for the tornado HTTPServer.
              See the tornado docs for details."""
          ),
      )
  
      jinja_environment_options = Dict(
          config=True,
          help=_("Supply extra arguments that will be passed to Jinja environment."),
      )
  
      jinja_template_vars = Dict(
          config=True,
          help=_("Extra variables to supply to jinja templates when rendering."),
      )
  
      base_url = Unicode(
          "/",
          config=True,
          help="""The base URL for the Jupyter server.
  
                         Leading and trailing slashes can be omitted,
                         and will automatically be added.
                         """,
      )
  
      @validate("base_url")
      def _update_base_url(self, proposal):
          value = proposal["value"]
          if not value.startswith("/"):
              value = "/" + value
          if not value.endswith("/"):
              value = value + "/"
          return value
  
      enable_mathjax = Bool(
          True,
          config=True,
          help="""Whether to enable MathJax for typesetting math/TeX
  
          MathJax is the javascript library Jupyter uses to render math/LaTeX. It is
          very large, so you may want to disable it if you have a slow internet
          connection, or for offline use of the notebook.
  
          When disabled, equations etc. will appear as their untransformed TeX source.
          """,
      )
  
      extra_static_paths = List(
          Unicode(),
          config=True,
          help="""Extra paths to search for serving static files.
  
          This allows adding javascript/css to be available from the Jupyter server machine,
          or overriding individual files in the IPython""",
      )
  
      @property
      def static_file_path(self):
          """return extra paths + the default location"""
          return self.extra_static_paths + [DEFAULT_STATIC_FILES_PATH]
  
      static_custom_path = List(
          Unicode(), help=_("""Path to search for custom.js, css""")
      )
  
      @default("static_custom_path")
      def _default_static_custom_path(self):
          return [
              os.path.join(d, "custom")
              for d in (self.config_dir, DEFAULT_STATIC_FILES_PATH)
          ]
  
      extra_template_paths = List(
          Unicode(),
          config=True,
          help=_(
              """Extra paths to search for serving jinja templates.
  
          Can be used to override templates from jupyter_server.templates."""
          ),
      )
  
      @property
      def template_file_path(self):
          """return extra paths + the default locations"""
          template_dirs = [
              os.path.join(os.path.dirname(__file__), 'templates'),
          ]
          return self.extra_template_paths + template_dirs + DEFAULT_TEMPLATE_PATH_LIST
  
      extra_services = List(
          Unicode(),
          config=True,
          help=_(
              """handlers that should be loaded at higher priority than the default services"""
          ),
      )
  
      default_services = List(
          Unicode(),
          config=False,  # Not user configurable!
          help="default services to load",
          default_value=(
              "jupyter_server.files.handlers",
              "jupyter_server.view.handlers",
              "jupyter_server.nbconvert.handlers",
              "jupyter_server.kernelspecs.handlers",
              "jupyter_server.edit.handlers",
              "jupyter_server.services.api.handlers",
              "jupyter_server.services.config.handlers",
              "jupyter_server.services.kernels.handlers",
              "jupyter_server.services.contents.handlers",
              "jupyter_server.services.sessions.handlers",
              "jupyter_server.services.nbconvert.handlers",
              "jupyter_server.services.kernelspecs.handlers",
              "jupyter_server.services.security.handlers",
              "jupyter_server.services.shutdown",
          ),
      )
  
      websocket_url = Unicode(
          "",
          config=True,
          help="""The base URL for websockets,
          if it differs from the HTTP server (hint: it almost certainly doesn't).
  
          Should be in the form of an HTTP origin: ws[s]://hostname[:port]
          """,
      )
  
      quit_button = Bool(
          True,
          config=True,
          help="""If True, display a button in the dashboard to quit
          (shutdown the Jupyter server).""",
      )
  
      contents_manager_class = Type(
          default_value=LargeFileManager,
          klass=ContentsManager,
          config=True,
          help=_("The content manager class to use."),
      )
  
      kernel_manager_class = Type(
          default_value=MappingKernelManager,
          config=True,
          help=_("The kernel manager class to use."),
      )
  
      session_manager_class = Type(
          default_value=SessionManager,
          config=True,
          help=_("The session manager class to use."),
      )
  
      config_manager_class = Type(
          default_value=ConfigManager,
          config=True,
          help=_("The config manager class to use"),
      )
  
      kernel_spec_manager = Instance(KernelSpecManager, allow_none=True)
  
      kernel_spec_manager_class = Type(
          default_value=KernelSpecManager,
          config=True,
          help="""
          The kernel spec manager class to use. Should be a subclass
          of `jupyter_client.kernelspec.KernelSpecManager`.
  
          The Api of KernelSpecManager is provisional and might change
          without warning between this version of Jupyter and the next stable one.
          """,
      )
  
      login_handler_class = Type(
          default_value=LoginHandler,
          klass=web.RequestHandler,
          config=True,
          help=_("The login handler class to use."),
      )
  
      logout_handler_class = Type(
          default_value=LogoutHandler,
          klass=web.RequestHandler,
          config=True,
          help=_("The logout handler class to use."),
      )
  
      trust_xheaders = Bool(
          False,
          config=True,
          help=(
              _(
                  "Whether to trust or not X-Scheme/X-Forwarded-Proto and X-Real-Ip/X-Forwarded-For headers"
                  "sent by the upstream reverse proxy. Necessary if the proxy handles SSL"
              )
          ),
      )
  
      info_file = Unicode()
  
      @default("info_file")
      def _default_info_file(self):
          info_file = "jpserver-%s.json" % os.getpid()
          return os.path.join(self.runtime_dir, info_file)
  
      pylab = Unicode(
          "disabled",
          config=True,
          help=_(
              """
          DISABLED: use %pylab or %matplotlib in the notebook to enable matplotlib.
          """
          ),
      )
  
      @observe("pylab")
      def _update_pylab(self, change):
          """when --pylab is specified, display a warning and exit"""
          if change["new"] != "warn":
              backend = " %s" % change["new"]
          else:
              backend = ""
          self.log.error(
              _("Support for specifying --pylab on the command line has been removed.")
          )
          self.log.error(
              _(
                  "Please use `%pylab{0}` or `%matplotlib{0}` in the notebook itself."
              ).format(backend)
          )
          self.exit(1)
  
      root_dir = Unicode(
          config=True, help=_("The directory to use for notebooks and kernels.")
      )
  
      @default("root_dir")
      def _default_root_dir(self):
          if self.file_to_run:
              return os.path.dirname(os.path.abspath(self.file_to_run))
          else:
              return py3compat.getcwd()
  
      @validate("root_dir")
      def _root_dir_validate(self, proposal):
          value = proposal["value"]
          # Strip any trailing slashes
          # *except* if it's root
          _, path = os.path.splitdrive(value)
          if path == os.sep:
              return value
          value = value.rstrip(os.sep)
          if not os.path.isabs(value):
              # If we receive a non-absolute path, make it absolute.
              value = os.path.abspath(value)
          if not os.path.isdir(value):
              raise TraitError(trans.gettext("No such notebook dir: '%r'") % value)
          return value
  
      @observe("root_dir")
      def _update_root_dir(self, change):
          """Do a bit of validation of the notebook dir."""
          # setting App.root_dir implies setting notebook and kernel dirs as well
          new = change["new"]
          self.config.FileContentsManager.root_dir = new
          self.config.MappingKernelManager.root_dir = new
  
      @observe("server_extensions")
      def _update_server_extensions(self, change):
          self.log.warning(_("server_extensions is deprecated, use jpserver_extensions"))
          self.server_extensions = change["new"]
  
      jpserver_extensions = Dict(
          {},
          config=True,
          help=(
              _(
                  "Dict of Python modules to load as notebook server extensions."
                  "Entry values can be used to enable and disable the loading of"
                  "the extensions. The extensions will be loaded in alphabetical "
                  "order."
              )
          ),
      )
  
      reraise_server_extension_failures = Bool(
          False,
          config=True,
          help=_("Reraise exceptions encountered loading server extensions?"),
      )
  
      iopub_msg_rate_limit = Float(
          1000,
          config=True,
          help=_(
              """(msgs/sec)
          Maximum rate at which messages can be sent on iopub before they are
          limited."""
          ),
      )
  
      iopub_data_rate_limit = Float(
          1000000,
          config=True,
          help=_(
              """(bytes/sec)
          Maximum rate at which stream output can be sent on iopub before they are
          limited."""
          ),
      )
  
      rate_limit_window = Float(
          3,
          config=True,
          help=_(
              """(sec) Time window used to
          check the message and data rate limits."""
          ),
      )
  
      shutdown_no_activity_timeout = Integer(
          0,
          config=True,
          help=(
              "Shut down the server after N seconds with no kernels or "
              "terminals running and no activity. "
              "This can be used together with culling idle kernels "
              "(MappingKernelManager.cull_idle_timeout) to "
              "shutdown the Jupyter server when it's not in use. This is not "
              "precisely timed: it may shut down up to a minute later. "
              "0 (the default) disables this automatic shutdown."
          ),
      )
  
      terminals_enabled = Bool(
          False,
          config=True,
          help=_(
              """Set to False to disable terminals.
  
           This does *not* make the server more secure by itself.
           Anything the user can in a terminal, they can also do in a notebook.
  
           Terminals may also be automatically disabled if the terminado package
           is not available.
           """
          ),
      )
  
      def parse_command_line(self, argv=None):
          super(ServerApp, self).parse_command_line(argv)
  
          if self.extra_args:
              arg0 = self.extra_args[0]
              f = os.path.abspath(arg0)
              self.argv.remove(arg0)
              if not os.path.exists(f):
                  self.log.critical(_("No such file or directory: %s"), f)
                  self.exit(1)
  
              # Use config here, to ensure that it takes higher priority than
              # anything that comes from the config dirs.
              c = Config()
              if os.path.isdir(f):
                  c.ServerApp.root_dir = f
              elif os.path.isfile(f):
                  c.ServerApp.file_to_run = f
              self.update_config(c)
  
      def init_configurables(self):
          self.kernel_spec_manager = self.kernel_spec_manager_class(parent=self)
          self.kernel_manager = self.kernel_manager_class(
              parent=self,
              log=self.log,
              connection_dir=self.runtime_dir,
              kernel_spec_manager=self.kernel_spec_manager,
          )
          self.contents_manager = self.contents_manager_class(parent=self, log=self.log)
          self.session_manager = self.session_manager_class(
              parent=self,
              log=self.log,
              kernel_manager=self.kernel_manager,
              contents_manager=self.contents_manager,
          )
          self.config_manager = self.config_manager_class(parent=self, log=self.log)
  
      def init_logging(self):
          # This prevents double log messages because tornado use a root logger that
          # self.log is a child of. The logging module dipatches log messages to a log
          # and all of its ancenstors until propagate is set to False.
          self.log.propagate = False
  
          for log in app_log, access_log, gen_log:
              # consistent log output name (ServerApp instead of tornado.access, etc.)
              log.name = self.log.name
          # hook up tornado 3's loggers to our app handlers
          logger = logging.getLogger("tornado")
          logger.propagate = True
          logger.parent = self.log
          logger.setLevel(self.log.level)
  
      def init_webapp(self):
          """initialize tornado webapp and httpserver"""
          self.tornado_settings["allow_origin"] = self.allow_origin
          self.tornado_settings[
              "websocket_compression_options"
          ] = self.websocket_compression_options
          if self.allow_origin_pat:
              self.tornado_settings["allow_origin_pat"] = re.compile(
                  self.allow_origin_pat
              )
          self.tornado_settings["allow_credentials"] = self.allow_credentials
          self.tornado_settings["cookie_options"] = self.cookie_options
          self.tornado_settings["token"] = self.token
          if (self.open_browser or self.file_to_run) and not self.password:
              self.one_time_token = binascii.hexlify(os.urandom(24)).decode("ascii")
              self.tornado_settings["one_time_token"] = self.one_time_token
  
          # ensure default_url starts with base_url
          if not self.default_url.startswith(self.base_url):
              self.default_url = url_path_join(self.base_url, self.default_url)
  
          if self.password_required and (not self.password):
              self.log.critical(
                  _("Jupyter servers are configured to only be run with a password.")
              )
              self.log.critical(_("Hint: run the following command to set a password"))
              self.log.critical(_("\t$ python -m jupyter_server.auth password"))
              sys.exit(1)
  
          self.web_app = ServerWebApplication(
              self,
              self.kernel_manager,
              self.contents_manager,
              self.session_manager,
              self.kernel_spec_manager,
              self.config_manager,
              self.extra_services,
              self.default_services,
              self.log,
              self.base_url,
              self.default_url,
              self.tornado_settings,
              self.jinja_environment_options,
          )
          ssl_options = self.ssl_options
          if self.certfile:
              ssl_options["certfile"] = self.certfile
          if self.keyfile:
              ssl_options["keyfile"] = self.keyfile
          if self.client_ca:
              ssl_options["ca_certs"] = self.client_ca
          if not ssl_options:
              # None indicates no SSL config
              ssl_options = None
          else:
              # SSL may be missing, so only import it if it's to be used
              import ssl
  
              # Disable SSLv3 by default, since its use is discouraged.
              ssl_options.setdefault("ssl_version", ssl.PROTOCOL_TLSv1)
              if ssl_options.get("ca_certs", False):
                  ssl_options.setdefault("cert_reqs", ssl.CERT_REQUIRED)
  
          self.login_handler_class.validate_security(self, ssl_options=ssl_options)
          self.http_server = httpserver.HTTPServer(
              self.web_app, ssl_options=ssl_options, xheaders=self.trust_xheaders
          )
  
          success = None
          for port in random_ports(self.port, self.port_retries + 1):
              try:
                  self.http_server.listen(port, self.ip)
              except socket.error as e:
                  if e.errno == errno.EADDRINUSE:
                      self.log.info(
                          _("The port %i is already in use, trying another port.") % port
                      )
                      continue
                  elif e.errno in (
                      errno.EACCES,
                      getattr(errno, "WSAEACCES", errno.EACCES),
                  ):
                      self.log.warning(_("Permission to listen on port %i denied") % port)
                      continue
                  else:
                      raise
              else:
                  self.port = port
                  success = True
                  break
          if not success:
              self.log.critical(
                  _(
                      "ERROR: the Jupyter server could not be started because "
                      "no available port could be found."
                  )
              )
              self.exit(1)
  
      @property
      def display_url(self):
          if self.custom_display_url:
              url = self.custom_display_url
              if not url.endswith("/"):
                  url += "/"
          else:
              if self.ip in ("", "0.0.0.0"):
                  ip = "(%s or 127.0.0.1)" % socket.gethostname()
              else:
                  ip = self.ip
              url = self._url(ip)
          if self.token:
              # Don't log full token if it came from config
              token = self.token if self._token_generated else "..."
              url = url_concat(url, {"token": token})
          return url
  
      @property
      def connection_url(self):
          ip = self.ip if self.ip else "localhost"
          return self._url(ip)
  
      def _url(self, ip):
          proto = "https" if self.certfile else "http"
          return "%s://%s:%i%s" % (proto, ip, self.port, self.base_url)
  
      def init_terminals(self):
          return
  
      def init_signal(self):
          if not sys.platform.startswith("win") and sys.stdin and sys.stdin.isatty():
              signal.signal(signal.SIGINT, self._handle_sigint)
          signal.signal(signal.SIGTERM, self._signal_stop)
          if hasattr(signal, "SIGUSR1"):
              # Windows doesn't support SIGUSR1
              signal.signal(signal.SIGUSR1, self._signal_info)
          if hasattr(signal, "SIGINFO"):
              # only on BSD-based systems
              signal.signal(signal.SIGINFO, self._signal_info)
  
      def _handle_sigint(self, sig, frame):
          """SIGINT handler spawns confirmation dialog"""
          # register more forceful signal handler for ^C^C case
          signal.signal(signal.SIGINT, self._signal_stop)
          # request confirmation dialog in bg thread, to avoid
          # blocking the App
          thread = threading.Thread(target=self._confirm_exit)
          thread.daemon = True
          thread.start()
  
      def _restore_sigint_handler(self):
          """callback for restoring original SIGINT handler"""
          signal.signal(signal.SIGINT, self._handle_sigint)
  
      def _confirm_exit(self):
          """confirm shutdown on ^C
  
          A second ^C, or answering 'y' within 5s will cause shutdown,
          otherwise original SIGINT handler will be restored.
  
          This doesn't work on Windows.
          """
          info = self.log.info
          info(_("interrupted"))
          print(self.notebook_info())
          yes = _("y")
          no = _("n")
          sys.stdout.write(_("Shutdown this Jupyter server (%s/[%s])? ") % (yes, no))
          sys.stdout.flush()
          r, w, x = select.select([sys.stdin], [], [], 5)
          if r:
              line = sys.stdin.readline()
              if line.lower().startswith(yes) and no not in line.lower():
                  self.log.critical(_("Shutdown confirmed"))
                  # schedule stop on the main thread,
                  # since this might be called from a signal handler
                  self.io_loop.add_callback_from_signal(self.io_loop.stop)
                  return
          else:
              print(_("No answer for 5s:"), end=" ")
          print(_("resuming operation..."))
          # no answer, or answer is no:
          # set it back to original SIGINT handler
          # use IOLoop.add_callback because signal.signal must be called
          # from main thread
          self.io_loop.add_callback_from_signal(self._restore_sigint_handler)
  
      def _signal_stop(self, sig, frame):
          self.log.critical(_("received signal %s, stopping"), sig)
          self.io_loop.add_callback_from_signal(self.io_loop.stop)
  
      def _signal_info(self, sig, frame):
          print(self.notebook_info())
  
      def init_components(self):
          """Check the components submodule, and warn if it's unclean"""
          # TODO: this should still check, but now we use bower, not git submodule
          pass
  
      def init_server_extensions(self):
          """Load any extensions specified by config.
  
          Import the module, then call the load_jupyter_server_extension function,
          if one exists.
  
          The extension API is experimental, and may change in future releases.
          """
  
          # Load server extensions with ConfigManager.
          # This enables merging on keys, which we want for extension enabling.
          # Regular config loading only merges at the class level,
          # so each level (user > env > system) clobbers the previous.
          config_path = jupyter_config_path()
          if self.config_dir not in config_path:
              # add self.config_dir to the front, if set manually
              config_path.insert(0, self.config_dir)
          manager = ConfigManager(read_config_path=config_path)
          section = manager.get(self.config_file_name)
          extensions = section.get("ServerApp", {}).get("jpserver_extensions", {})
  
          for modulename, enabled in self.jpserver_extensions.items():
              if modulename not in extensions:
                  # not present in `extensions` means it comes from Python config,
                  # so we need to add it.
                  # Otherwise, trust ConfigManager to have loaded it.
                  extensions[modulename] = enabled
  
          for modulename, enabled in sorted(extensions.items()):
              if enabled:
                  try:
                      mod = importlib.import_module(modulename)
                      func = getattr(mod, "load_jupyter_server_extension", None)
                      if func is not None:
                          func(self)
                  except Exception:
                      if self.reraise_server_extension_failures:
                          raise
                      self.log.warning(
                          _("Error loading server extension %s"),
                          modulename,
                          exc_info=True,
                      )
  
      def init_mime_overrides(self):
          # On some Windows machines, an application has registered an incorrect
          # mimetype for CSS in the registry. Tornado uses this when serving
          # .css files, causing browsers to reject the stylesheet. We know the
          # mimetype always needs to be text/css, so we override it here.
          mimetypes.add_type("text/css", ".css")
  
      def shutdown_no_activity(self):
          """Shutdown server on timeout when there are no kernels or terminals."""
          km = self.kernel_manager
          if len(km) != 0:
              return  # Kernels still running
  
          try:
              term_mgr = self.web_app.settings["terminal_manager"]
          except KeyError:
              pass  # Terminals not enabled
          else:
              if term_mgr.terminals:
                  return  # Terminals still running
  
          seconds_since_active = (utcnow() - self.web_app.last_activity()).total_seconds()
          self.log.debug("No activity for %d seconds.", seconds_since_active)
          if seconds_since_active > self.shutdown_no_activity_timeout:
              self.log.info(
                  "No kernels or terminals for %d seconds; shutting down.",
                  seconds_since_active,
              )
              self.stop()
  
      def init_shutdown_no_activity(self):
          if self.shutdown_no_activity_timeout > 0:
              self.log.info(
                  "Will shut down after %d seconds with no kernels or terminals.",
                  self.shutdown_no_activity_timeout,
              )
              pc = ioloop.PeriodicCallback(self.shutdown_no_activity, 60000)
              pc.start()
  
      @catch_config_error
      def initialize(self, argv=None, load_extensions=True):
          super(ServerApp, self).initialize(argv)
          self.init_logging()
          if self._dispatching:
              return
          self.init_configurables()
          self.init_components()
          self.init_webapp()
          self.init_terminals()
          self.init_signal()
          if load_extensions is True:
              self.init_server_extensions()
          self.init_mime_overrides()
          self.init_shutdown_no_activity()
  
      def cleanup_kernels(self):
          """Shutdown all kernels.
  
          The kernels will shutdown themselves when this process no longer exists,
          but explicit shutdown allows the KernelManagers to cleanup the connection files.
          """
          n_kernels = len(self.kernel_manager.list_kernel_ids())
          kernel_msg = trans.ngettext(
              "Shutting down %d kernel", "Shutting down %d kernels", n_kernels
          )
          self.log.info(kernel_msg % n_kernels)
          self.kernel_manager.shutdown_all()
  
      def notebook_info(self, kernel_count=True):
          "Return the current working directory and the server url information"
          info = self.contents_manager.info_string() + "\n"
          if kernel_count:
              n_kernels = len(self.kernel_manager.list_kernel_ids())
              kernel_msg = trans.ngettext(
                  "%d active kernel", "%d active kernels", n_kernels
              )
              info += kernel_msg % n_kernels
              info += "\n"
          # Format the info so that the URL fits on a single line in 80 char display
          info += _("The Jupyter Server is running at:\n%s") % self.display_url
          return info
  
      def server_info(self):
          """Return a JSONable dict of information about this server."""
          return {
              "url": self.connection_url,
              "hostname": self.ip if self.ip else "localhost",
              "port": self.port,
              "secure": bool(self.certfile),
              "base_url": self.base_url,
              "token": self.token,
              "root_dir": os.path.abspath(self.root_dir),
              "password": bool(self.password),
              "pid": os.getpid(),
          }
  
      def write_server_info_file(self):
          """Write the result of server_info() to the JSON file info_file."""
          try:
              with open(self.info_file, "w") as f:
                  json.dump(self.server_info(), f, indent=2, sort_keys=True)
          except OSError as e:
              self.log.error(
                  _("Failed to write server-info to %s: %s"), self.info_file, e
              )
  
      def remove_server_info_file(self):
          """Remove the jpserver-<pid>.json file created for this server.
  
          Ignores the error raised when the file has already been removed.
          """
          try:
              os.unlink(self.info_file)
          except OSError as e:
              if e.errno != errno.ENOENT:
                  raise
  
      def start(self):
          """ Start the Jupyter server app, after initialization
  
          This method takes no arguments so all configuration and initialization
          must be done prior to calling this method."""
  
          super(ServerApp, self).start()
  
          if not self.allow_root:
              # check if we are running as root, and abort if it's not allowed
              try:
                  uid = os.geteuid()
              except AttributeError:
                  uid = (
                      -1
                  )  # anything nonzero here, since we can't check UID assume non-root
              if uid == 0:
                  self.log.critical(
                      _("Running as root is not recommended. Use --allow-root to bypass.")
                  )
                  self.exit(1)
  
          info = self.log.info
          for line in self.notebook_info(kernel_count=False).split("\n"):
              info(line)
          info(
              _(
                  "Use Control-C to stop this server and shut down all kernels (twice to skip confirmation)."
              )
          )
          if "dev" in jupyter_server.__version__:
              info(
                  _(
                      "Welcome to Project Jupyter! Explore the various tools available"
                      " and their corresponding documentation. If you are interested"
                      " in contributing to the platform, please visit the community"
                      "resources section at https://jupyter.org/community.html."
                  )
              )
  
          self.write_server_info_file()
  
          if self.open_browser or self.file_to_run:
              try:
                  browser = webbrowser.get(self.browser or None)
              except webbrowser.Error as e:
                  self.log.warning(_("No web browser found: %s.") % e)
                  browser = None
  
              if self.file_to_run:
                  if not os.path.exists(self.file_to_run):
                      self.log.critical(_("%s does not exist") % self.file_to_run)
                      self.exit(1)
  
                  relpath = os.path.relpath(self.file_to_run, self.root_dir)
                  uri_parts = []
                  if self.file_to_run_url:
                      uri_parts.append(self.file_to_run_url)
                  uri_parts.extend(relpath.split(os.sep))
                  uri = url_escape(url_path_join(*uri_parts))
              else:
                  uri = self.base_url
              if self.one_time_token:
                  uri = url_concat(uri, {"token": self.one_time_token})
              if browser:
                  b = lambda: browser.open(
                      url_path_join(self.connection_url, uri),
                      new=self.webbrowser_open_new,
                  )
                  threading.Thread(target=b).start()
  
          if self.token and self._token_generated:
              # log full URL with generated token, so there's a copy/pasteable link
              # with auth info.
              self.log.critical(
                  "\n".join(
                      [
                          "\n",
                          "Copy/paste this URL into your browser when you connect for the first time,",
                          "to login with a token:",
                          "    %s" % self.display_url,
                      ]
                  )
              )
  
          self.io_loop = ioloop.IOLoop.current()
          if sys.platform.startswith("win"):
              # add no-op to wake every 5s
              # to handle signals that may be ignored by the inner loop
              pc = ioloop.PeriodicCallback(lambda: None, 5000)
              pc.start()
          try:
              self.io_loop.start()
          except KeyboardInterrupt:
              info(_("Interrupted..."))
          finally:
              self.remove_server_info_file()
              self.cleanup_kernels()
  
      def stop(self):
          def _stop():
              self.http_server.stop()
              self.io_loop.stop()
  
          self.io_loop.add_callback(_stop)
  
  
  def list_running_servers(runtime_dir=None):
      """Iterate over the server info files of running notebook servers.
  
      Given a runtime directory, find jpserver-* files in the security directory,
      and yield dicts of their information, each one pertaining to
      a currently running notebook server instance.
      """
      if runtime_dir is None:
          runtime_dir = jupyter_runtime_dir()
  
      # The runtime dir might not exist
      if not os.path.isdir(runtime_dir):
          return
  
      for file_name in os.listdir(runtime_dir):
          if file_name.startswith("jpserver-"):
              with io.open(os.path.join(runtime_dir, file_name), encoding="utf-8") as f:
                  info = json.load(f)
  
              # Simple check whether that process is really still running
              # Also remove leftover files from IPython 2.x without a pid field
              if ("pid" in info) and check_pid(info["pid"]):
                  yield info
              else:
                  # If the process has died, try to delete its info file
                  try:
                      os.unlink(os.path.join(runtime_dir, file_name))
                  except OSError:
                      pass  # TODO: This should warn or log or something
  
  
  # -----------------------------------------------------------------------------
  # Main entry point
  # -----------------------------------------------------------------------------
  
  main = launch_new_instance = ServerApp.launch_instance
  