IPython/html/notebookapp.py

# coding: utf-8
"""A tornado based IPython notebook server.

Authors:

* Brian Granger
"""
from __future__ import print_function
#-----------------------------------------------------------------------------
#  Copyright (C) 2013  The IPython Development Team
#
#  Distributed under the terms of the BSD License.  The full license is in
#  the file COPYING, distributed as part of this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

# stdlib
import errno
import io
import json
import logging
import os
import random
import select
import signal
import socket
import sys
import threading
import time
import webbrowser


# Third party
# check for pyzmq 2.1.11
from IPython.utils.zmqrelated import check_for_zmq
check_for_zmq('2.1.11', 'IPython.html')

from jinja2 import Environment, FileSystemLoader

# 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
msg = "The IPython Notebook requires tornado >= 3.1.0"
try:
    import tornado
except ImportError:
    raise ImportError(msg)
try:
    version_info = tornado.version_info
except AttributeError:
    raise ImportError(msg + ", but you have < 1.1.0")
if version_info < (3,1,0):
    raise ImportError(msg + ", but you have %s" % tornado.version)

from tornado import httpserver
from tornado import web

# Our own libraries
from IPython.html import DEFAULT_STATIC_FILES_PATH
from .base.handlers import Template404
from .log import log_request
from .services.kernels.kernelmanager import MappingKernelManager
from .services.notebooks.nbmanager import NotebookManager
from .services.notebooks.filenbmanager import FileNotebookManager
from .services.clusters.clustermanager import ClusterManager
from .services.sessions.sessionmanager import SessionManager

from .base.handlers import AuthenticatedFileHandler, FileFindHandler

from IPython.config.application import catch_config_error, boolean_flag
from IPython.core.application import BaseIPythonApplication
from IPython.core.profiledir import ProfileDir
from IPython.consoleapp import IPythonConsoleApp
from IPython.kernel import swallow_argv
from IPython.kernel.zmq.session import default_secure
from IPython.kernel.zmq.kernelapp import (
    kernel_flags,
    kernel_aliases,
)
from IPython.utils.importstring import import_item
from IPython.utils.localinterfaces import localhost
from IPython.utils import submodule
from IPython.utils.traitlets import (
    Dict, Unicode, Integer, List, Bool, Bytes,
    DottedObjectName, TraitError,
)
from IPython.utils import py3compat
from IPython.utils.path import filefind, get_ipython_dir

from .utils import url_path_join

#-----------------------------------------------------------------------------
# Module globals
#-----------------------------------------------------------------------------

_examples = """
ipython notebook                       # start the notebook
ipython notebook --profile=sympy       # use the sympy profile
ipython notebook --certfile=mycert.pem # use SSL/TLS certificate
"""

#-----------------------------------------------------------------------------
# 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."""
    name = 'IPython.html.' + name
    mod = __import__(name, fromlist=['default_handlers'])
    return mod.default_handlers

#-----------------------------------------------------------------------------
# The Tornado web application
#-----------------------------------------------------------------------------

class NotebookWebApplication(web.Application):

    def __init__(self, ipython_app, kernel_manager, notebook_manager,
                 cluster_manager, session_manager, log, base_url,
                 settings_overrides, jinja_env_options):

        settings = self.init_settings(
            ipython_app, kernel_manager, notebook_manager, cluster_manager,
            session_manager, log, base_url, settings_overrides, jinja_env_options)
        handlers = self.init_handlers(settings)

        super(NotebookWebApplication, self).__init__(handlers, **settings)

    def init_settings(self, ipython_app, kernel_manager, notebook_manager,
                      cluster_manager, session_manager, log, base_url,
                      settings_overrides, jinja_env_options=None):
        # Python < 2.6.5 doesn't accept unicode keys in f(**kwargs), and
        # base_url will always be unicode, which will in turn
        # make the patterns unicode, and ultimately result in unicode
        # keys in kwargs to handler._execute(**kwargs) in tornado.
        # This enforces that base_url be ascii in that situation.
        # 
        # Note that the URLs these patterns check against are escaped,
        # and thus guaranteed to be ASCII: 'héllo' is really 'h%C3%A9llo'.
        base_url = py3compat.unicode_to_str(base_url, 'ascii')
        template_path = settings_overrides.get("template_path", os.path.join(os.path.dirname(__file__), "templates"))
        jenv_opt = jinja_env_options if jinja_env_options else {}
        env = Environment(loader=FileSystemLoader(template_path),**jenv_opt )
        settings = dict(
            # basics
            log_function=log_request,
            base_url=base_url,
            template_path=template_path,
            static_path=ipython_app.static_file_path,
            static_handler_class = FileFindHandler,
            static_url_prefix = url_path_join(base_url,'/static/'),
            
            # authentication
            cookie_secret=ipython_app.cookie_secret,
            login_url=url_path_join(base_url,'/login'),
            password=ipython_app.password,
            
            # managers
            kernel_manager=kernel_manager,
            notebook_manager=notebook_manager,
            cluster_manager=cluster_manager,
            session_manager=session_manager,

            # IPython stuff
            nbextensions_path = ipython_app.nbextensions_path,
            mathjax_url=ipython_app.mathjax_url,
            config=ipython_app.config,
            jinja2_env=env,
        )

        # 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.
        handlers = []
        handlers.extend(load_handlers('base.handlers'))
        handlers.extend(load_handlers('tree.handlers'))
        handlers.extend(load_handlers('auth.login'))
        handlers.extend(load_handlers('auth.logout'))
        handlers.extend(load_handlers('notebook.handlers'))
        handlers.extend(load_handlers('nbconvert.handlers'))
        handlers.extend(load_handlers('services.kernels.handlers'))
        handlers.extend(load_handlers('services.notebooks.handlers'))
        handlers.extend(load_handlers('services.clusters.handlers'))
        handlers.extend(load_handlers('services.sessions.handlers'))
        handlers.extend(load_handlers('services.nbconvert.handlers'))
        # FIXME: /files/ should be handled by the Contents service when it exists
        nbm = settings['notebook_manager']
        if hasattr(nbm, 'notebook_dir'):
            handlers.extend([
            (r"/files/(.*)", AuthenticatedFileHandler, {'path' : nbm.notebook_dir}),
            (r"/nbextensions/(.*)", FileFindHandler, {'path' : settings['nbextensions_path']}),
        ])
        # 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


class NbserverListApp(BaseIPythonApplication):
    
    description="List currently running notebook servers in this profile."
    
    flags = dict(
        json=({'NbserverListApp': {'json': True}},
              "Produce machine-readable JSON output."),
    )
    
    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.")

    def start(self):
        if not self.json:
            print("Currently running servers:")
        for serverinfo in list_running_servers(self.profile):
            if self.json:
                print(json.dumps(serverinfo))
            else:
                print(serverinfo['url'], "::", serverinfo['notebook_dir'])

#-----------------------------------------------------------------------------
# Aliases and Flags
#-----------------------------------------------------------------------------

flags = dict(kernel_flags)
flags['no-browser']=(
    {'NotebookApp' : {'open_browser' : False}},
    "Don't open the notebook in a browser after startup."
)
flags['no-mathjax']=(
    {'NotebookApp' : {'enable_mathjax' : False}},
    """Disable MathJax
    
    MathJax is the javascript library IPython 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.
    """
)

# Add notebook manager flags
flags.update(boolean_flag('script', 'FileNotebookManager.save_script',
               'Auto-save a .py script everytime the .ipynb notebook is saved',
               'Do not auto-save .py scripts for every notebook'))

# the flags that are specific to the frontend
# these must be scrubbed before being passed to the kernel,
# or it will raise an error on unrecognized flags
notebook_flags = ['no-browser', 'no-mathjax', 'script', 'no-script']

aliases = dict(kernel_aliases)

aliases.update({
    'ip': 'NotebookApp.ip',
    'port': 'NotebookApp.port',
    'port-retries': 'NotebookApp.port_retries',
    'transport': 'KernelManager.transport',
    'keyfile': 'NotebookApp.keyfile',
    'certfile': 'NotebookApp.certfile',
    'notebook-dir': 'NotebookApp.notebook_dir',
    'browser': 'NotebookApp.browser',
})

# remove ipkernel flags that are singletons, and don't make sense in
# multi-kernel evironment:
aliases.pop('f', None)

notebook_aliases = [u'port', u'port-retries', u'ip', u'keyfile', u'certfile',
                    u'notebook-dir', u'profile', u'profile-dir']

#-----------------------------------------------------------------------------
# NotebookApp
#-----------------------------------------------------------------------------

class NotebookApp(BaseIPythonApplication):

    name = 'ipython-notebook'
    
    description = """
        The IPython HTML Notebook.
        
        This launches a Tornado based HTML Notebook Server that serves up an
        HTML5/Javascript Notebook client.
    """
    examples = _examples
    
    classes = IPythonConsoleApp.classes + [MappingKernelManager, NotebookManager,
        FileNotebookManager]
    flags = Dict(flags)
    aliases = Dict(aliases)
    
    subcommands = dict(
        list=(NbserverListApp, NbserverListApp.description.splitlines()[0]),
    )

    kernel_argv = List(Unicode)

    def _log_level_default(self):
        return logging.INFO

    def _log_format_default(self):
        """override default log format to include time"""
        return u"%(asctime)s.%(msecs).03d [%(name)s]%(highlevel)s %(message)s"

    # create requested profiles by default, if they don't exist:
    auto_create = Bool(True)

    # file to be opened in the notebook server
    file_to_run = Unicode('')

    # Network related information.

    ip = Unicode(config=True,
        help="The IP address the notebook server will listen on."
    )
    def _ip_default(self):
        return localhost()

    def _ip_changed(self, name, old, new):
        if new == u'*': self.ip = u''

    port = Integer(8888, config=True,
        help="The port the notebook 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."""
    )
    
    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 Notebook.
        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).
        """
    )
    def _cookie_secret_default(self):
        return os.urandom(1024)

    password = Unicode(u'', config=True,
                      help="""Hashed password to use for web authentication.

                      To generate, type in a python/IPython shell:

                        from IPython.lib import passwd; passwd()

                      The string should be of the form type:salt:hashed-password.
                      """
    )

    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
                        (NotebookApp.browser) configuration option.
                        """)

    browser = Unicode(u'', config=True,
                      help="""Specify what command to use to invoke a web
                      browser when opening the notebook. 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.
                      """)
    
    webapp_settings = Dict(config=True,
            help="Supply overrides for the tornado.web.Application that the "
                 "IPython notebook uses.")

    jinja_environment_options = Dict(config=True, 
            help="Supply extra arguments that will be passed to Jinja environment.")

    
    enable_mathjax = Bool(True, config=True,
        help="""Whether to enable MathJax for typesetting math/TeX

        MathJax is the javascript library IPython 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.
        """
    )
    def _enable_mathjax_changed(self, name, old, new):
        """set mathjax url to empty if mathjax is disabled"""
        if not new:
            self.mathjax_url = u''

    base_url = Unicode('/', config=True,
                               help='''The base URL for the notebook server.

                               Leading and trailing slashes can be omitted,
                               and will automatically be added.
                               ''')
    def _base_url_changed(self, name, old, new):
        if not new.startswith('/'):
            self.base_url = '/'+new
        elif not new.endswith('/'):
            self.base_url = new+'/'
    
    base_project_url = Unicode('/', config=True, help="""DEPRECATED use base_url""")
    def _base_project_url_changed(self, name, old, new):
        self.log.warn("base_project_url is deprecated, use base_url")
        self.base_url = new

    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 notebook server machine,
        or overriding individual files in the IPython"""
    )
    def _extra_static_paths_default(self):
        return [os.path.join(self.profile_dir.location, 'static')]
    
    @property
    def static_file_path(self):
        """return extra paths + the default location"""
        return self.extra_static_paths + [DEFAULT_STATIC_FILES_PATH]
    
    nbextensions_path = List(Unicode, config=True,
        help="""paths for Javascript extensions. By default, this is just IPYTHONDIR/nbextensions"""
    )
    def _nbextensions_path_default(self):
        return [os.path.join(get_ipython_dir(), 'nbextensions')]

    mathjax_url = Unicode("", config=True,
        help="""The url for MathJax.js."""
    )
    def _mathjax_url_default(self):
        if not self.enable_mathjax:
            return u''
        static_url_prefix = self.webapp_settings.get("static_url_prefix",
                         url_path_join(self.base_url, "static")
        )
        
        # try local mathjax, either in nbextensions/mathjax or static/mathjax
        for (url_prefix, search_path) in [
            (url_path_join(self.base_url, "nbextensions"), self.nbextensions_path),
            (static_url_prefix, self.static_file_path),
        ]:
            self.log.debug("searching for local mathjax in %s", search_path)
            try:
                mathjax = filefind(os.path.join('mathjax', 'MathJax.js'), search_path)
            except IOError:
                continue
            else:
                url = url_path_join(url_prefix, u"mathjax/MathJax.js")
                self.log.info("Serving local MathJax from %s at %s", mathjax, url)
                return url
        
        # no local mathjax, serve from CDN
        if self.certfile:
            # HTTPS: load from Rackspace CDN, because SSL certificate requires it
            host = u"https://c328740.ssl.cf1.rackcdn.com"
        else:
            host = u"http://cdn.mathjax.org"
        
        url = host + u"/mathjax/latest/MathJax.js"
        self.log.info("Using MathJax from CDN: %s", url)
        return url
    
    def _mathjax_url_changed(self, name, old, new):
        if new and not self.enable_mathjax:
            # enable_mathjax=False overrides mathjax_url
            self.mathjax_url = u''
        else:
            self.log.info("Using MathJax: %s", new)

    notebook_manager_class = DottedObjectName('IPython.html.services.notebooks.filenbmanager.FileNotebookManager',
        config=True,
        help='The notebook manager 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()

    def _info_file_default(self):
        info_file = "nbserver-%s.json"%os.getpid()
        return os.path.join(self.profile_dir.security_dir, info_file)
    
    notebook_dir = Unicode(py3compat.getcwd(), config=True,
        help="The directory to use for notebooks and kernels."
    )

    def _notebook_dir_changed(self, name, old, new):
        """Do a bit of validation of the notebook dir."""
        if not os.path.isabs(new):
            # If we receive a non-absolute path, make it absolute.
            self.notebook_dir = os.path.abspath(new)
            return
        if not os.path.isdir(new):
            raise TraitError("No such notebook dir: %r" % new)
        
        # setting App.notebook_dir implies setting notebook and kernel dirs as well
        self.config.FileNotebookManager.notebook_dir = new
        self.config.MappingKernelManager.root_dir = new
        

    def parse_command_line(self, argv=None):
        super(NotebookApp, 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)
            if os.path.isdir(f):
                self.notebook_dir = f
            elif os.path.isfile(f):
                self.file_to_run = f

    def init_kernel_argv(self):
        """construct the kernel arguments"""
        # Scrub frontend-specific flags
        self.kernel_argv = swallow_argv(self.argv, notebook_aliases, notebook_flags)
        if any(arg.startswith(u'--pylab') for arg in self.kernel_argv):
            self.log.warn('\n    '.join([
                "Starting all kernels in pylab mode is not recommended,",
                "and will be disabled in a future release.",
                "Please use the %matplotlib magic to enable matplotlib instead.",
                "pylab implies many imports, which can have confusing side effects",
                "and harm the reproducibility of your notebooks.",
            ]))
        # Kernel should inherit default config file from frontend
        self.kernel_argv.append("--IPKernelApp.parent_appname='%s'" % self.name)
        # Kernel should get *absolute* path to profile directory
        self.kernel_argv.extend(["--profile-dir", self.profile_dir.location])

    def init_configurables(self):
        # force Session default to be secure
        default_secure(self.config)
        self.kernel_manager = MappingKernelManager(
            parent=self, log=self.log, kernel_argv=self.kernel_argv,
            connection_dir = self.profile_dir.security_dir,
        )
        kls = import_item(self.notebook_manager_class)
        self.notebook_manager = kls(parent=self, log=self.log)
        self.session_manager = SessionManager(parent=self, log=self.log)
        self.cluster_manager = ClusterManager(parent=self, log=self.log)
        self.cluster_manager.update_profiles()

    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
        
        # hook up tornado 3's loggers to our app handlers
        for name in ('access', 'application', 'general'):
            logger = logging.getLogger('tornado.%s' % name)
            logger.parent = self.log
            logger.setLevel(self.log.level)
    
    def init_webapp(self):
        """initialize tornado webapp and httpserver"""
        self.web_app = NotebookWebApplication(
            self, self.kernel_manager, self.notebook_manager, 
            self.cluster_manager, self.session_manager,
            self.log, self.base_url, self.webapp_settings,
            self.jinja_environment_options
        )
        if self.certfile:
            ssl_options = dict(certfile=self.certfile)
            if self.keyfile:
                ssl_options['keyfile'] = self.keyfile
        else:
            ssl_options = None
        self.web_app.password = self.password
        self.http_server = httpserver.HTTPServer(self.web_app, ssl_options=ssl_options,
                                                 xheaders=self.trust_xheaders)
        if not self.ip:
            warning = "WARNING: The notebook server is listening on all IP addresses"
            if ssl_options is None:
                self.log.critical(warning + " and not using encryption. This "
                    "is not recommended.")
            if not self.password:
                self.log.critical(warning + " and not using authentication. "
                    "This is highly insecure and not recommended.")
        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 random port.' % port)
                    continue
                elif e.errno in (errno.EACCES, getattr(errno, 'WSAEACCES', errno.EACCES)):
                    self.log.warn("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 notebook server could not be started because '
                              'no available port could be found.')
            self.exit(1)
    
    @property
    def display_url(self):
        ip = self.ip if self.ip else '[all ip addresses on your system]'
        return self._url(ip)

    @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_signal(self):
        if not sys.platform.startswith('win'):
            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.
        """
        # FIXME: remove this delay when pyzmq dependency is >= 2.1.11
        time.sleep(0.1)
        info = self.log.info
        info('interrupted')
        print(self.notebook_info())
        sys.stdout.write("Shutdown this notebook server (y/[n])? ")
        sys.stdout.flush()
        r,w,x = select.select([sys.stdin], [], [], 5)
        if r:
            line = sys.stdin.readline()
            if line.lower().startswith('y'):
                self.log.critical("Shutdown confirmed")
                ioloop.IOLoop.instance().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
        ioloop.IOLoop.instance().add_callback(self._restore_sigint_handler)
    
    def _signal_stop(self, sig, frame):
        self.log.critical("received signal %s, stopping", sig)
        ioloop.IOLoop.instance().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"""
        status = submodule.check_submodule_status()
        if status == 'missing':
            self.log.warn("components submodule missing, running `git submodule update`")
            submodule.update_submodules(submodule.ipython_parent())
        elif status == 'unclean':
            self.log.warn("components submodule unclean, you may see 404s on static/components")
            self.log.warn("run `setup.py submodule` or `git submodule update` to update")
    
    @catch_config_error
    def initialize(self, argv=None):
        super(NotebookApp, self).initialize(argv)
        self.init_logging()
        self.init_kernel_argv()
        self.init_configurables()
        self.init_components()
        self.init_webapp()
        self.init_signal()

    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.
        """
        self.log.info('Shutting down kernels')
        self.kernel_manager.shutdown_all()

    def notebook_info(self):
        "Return the current working directory and the server url information"
        info = self.notebook_manager.info_string() + "\n"
        info += "%d active kernels \n" % len(self.kernel_manager._kernels)
        return info + "The IPython Notebook is running at: %s" % self.display_url

    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,
                'notebook_dir': os.path.abspath(self.notebook_dir),
               }

    def write_server_info_file(self):
        """Write the result of server_info() to the JSON file info_file."""
        with open(self.info_file, 'w') as f:
            json.dump(self.server_info(), f, indent=2)

    def remove_server_info_file(self):
        """Remove the nbserver-<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 IPython Notebook server app, after initialization
        
        This method takes no arguments so all configuration and initialization
        must be done prior to calling this method."""
        if self.subapp is not None:
            return self.subapp.start()

        info = self.log.info
        for line in self.notebook_info().split("\n"):
            info(line)
        info("Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).")

        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.warn('No web browser found: %s.' % e)
                browser = None
            
            f = self.file_to_run
            if f:
                nbdir = os.path.abspath(self.notebook_manager.notebook_dir)
                if f.startswith(nbdir):
                    f = f[len(nbdir):]
                else:
                    self.log.warn(
                        "Probably won't be able to open notebook %s "
                        "because it is not in notebook_dir %s",
                        f, nbdir,
                    )

            if os.path.isfile(self.file_to_run):
                url = url_path_join('notebooks', f)
            else:
                url = url_path_join('tree', f)
            if browser:
                b = lambda : browser.open("%s%s" % (self.connection_url, url),
                                          new=2)
                threading.Thread(target=b).start()
        try:
            ioloop.IOLoop.instance().start()
        except KeyboardInterrupt:
            info("Interrupted...")
        finally:
            self.cleanup_kernels()
            self.remove_server_info_file()


def list_running_servers(profile='default'):
    """Iterate over the server info files of running notebook servers.
    
    Given a profile name, find nbserver-* files in the security directory of
    that profile, and yield dicts of their information, each one pertaining to
    a currently running notebook server instance.
    """
    pd = ProfileDir.find_profile_dir_by_name(get_ipython_dir(), name=profile)
    for file in os.listdir(pd.security_dir):
        if file.startswith('nbserver-'):
            with io.open(os.path.join(pd.security_dir, file), encoding='utf-8') as f:
                yield json.load(f)

#-----------------------------------------------------------------------------
# Main entry point
#-----------------------------------------------------------------------------

launch_new_instance = NotebookApp.launch_instance