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handlers.py
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handlers.py
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"""
Authenticated HTTP proxy for Jupyter Notebooks
Some original inspiration from https://github.com/senko/tornado-proxy
"""
import inspect
import socket
import os
from urllib.parse import urlunparse, urlparse
import aiohttp
from asyncio import Lock
from tornado import gen, web, httpclient, httputil, process, websocket, ioloop, version_info
from notebook.utils import url_path_join
from notebook.base.handlers import IPythonHandler, utcnow
from .websocket import WebSocketHandlerMixin, pingable_ws_connect
from simpervisor import SupervisedProcess
class AddSlashHandler(IPythonHandler):
"""Add trailing slash to URLs that need them."""
@web.authenticated
def get(self, *args):
src = urlparse(self.request.uri)
dest = src._replace(path=src.path + '/')
self.redirect(urlunparse(dest))
class LocalProxyHandler(WebSocketHandlerMixin, IPythonHandler):
def __init__(self, *args, **kwargs):
self.proxy_base = ''
self.absolute_url = kwargs.pop('absolute_url', False)
super().__init__(*args, **kwargs)
async def open(self, port, proxied_path=''):
"""
Called when a client opens a websocket connection.
We establish a websocket connection to the proxied backend &
set up a callback to relay messages through.
"""
if not proxied_path.startswith('/'):
proxied_path = '/' + proxied_path
client_uri = self.get_client_uri('ws', port, proxied_path)
headers = self.request.headers
def message_cb(message):
"""
Callback when the backend sends messages to us
We just pass it back to the frontend
"""
# Websockets support both string (utf-8) and binary data, so let's
# make sure we signal that appropriately when proxying
self._record_activity()
if message is None:
self.close()
else:
self.write_message(message, binary=isinstance(message, bytes))
def ping_cb(data):
"""
Callback when the backend sends pings to us.
We just pass it back to the frontend.
"""
self._record_activity()
self.ping(data)
async def start_websocket_connection():
self.log.info('Trying to establish websocket connection to {}'.format(client_uri))
self._record_activity()
request = httpclient.HTTPRequest(url=client_uri, headers=headers)
self.ws = await pingable_ws_connect(request=request,
on_message_callback=message_cb, on_ping_callback=ping_cb)
self._record_activity()
self.log.info('Websocket connection established to {}'.format(client_uri))
ioloop.IOLoop.current().add_callback(start_websocket_connection)
def on_message(self, message):
"""
Called when we receive a message from our client.
We proxy it to the backend.
"""
self._record_activity()
if hasattr(self, 'ws'):
self.ws.write_message(message, binary=isinstance(message, bytes))
def on_ping(self, data):
"""
Called when the client pings our websocket connection.
We proxy it to the backend.
"""
self.log.debug('jupyter_server_proxy: on_ping: {}'.format(data))
self._record_activity()
if hasattr(self, 'ws'):
self.ws.protocol.write_ping(data)
def on_pong(self, data):
"""
Called when we receive a ping back.
"""
self.log.debug('jupyter_server_proxy: on_pong: {}'.format(data))
def on_close(self):
"""
Called when the client closes our websocket connection.
We close our connection to the backend too.
"""
if hasattr(self, 'ws'):
self.ws.close()
def _record_activity(self):
"""Record proxied activity as API activity
avoids proxied traffic being ignored by the notebook's
internal idle-shutdown mechanism
"""
self.settings['api_last_activity'] = utcnow()
def _get_context_path(self, port):
"""
Some applications need to know where they are being proxied from.
This is either:
- {base_url}/proxy/{port}
- {base_url}/proxy/absolute/{port}
- {base_url}/{proxy_base}
"""
if self.proxy_base:
return url_path_join(self.base_url, self.proxy_base)
if self.absolute_url:
return url_path_join(self.base_url, 'proxy', 'absolute', str(port))
else:
return url_path_join(self.base_url, 'proxy', str(port))
def get_client_uri(self, protocol, port, proxied_path):
context_path = self._get_context_path(port)
if self.absolute_url:
client_path = url_path_join(context_path, proxied_path)
else:
client_path = proxied_path
client_uri = '{protocol}://{host}:{port}{path}'.format(
protocol=protocol,
host='localhost',
port=port,
path=client_path
)
if self.request.query:
client_uri += '?' + self.request.query
return client_uri
def _build_proxy_request(self, port, proxied_path, body):
headers = self.proxy_request_headers()
client_uri = self.get_client_uri('http', port, proxied_path)
# Some applications check X-Forwarded-Context and X-ProxyContextPath
# headers to see if and where they are being proxied from.
if not self.absolute_url:
context_path = self._get_context_path(port)
headers['X-Forwarded-Context'] = context_path
headers['X-ProxyContextPath'] = context_path
req = httpclient.HTTPRequest(
client_uri, method=self.request.method, body=body,
headers=headers, **self.proxy_request_options())
return req
@web.authenticated
async def proxy(self, port, proxied_path):
'''
This serverextension handles:
{base_url}/proxy/{port([0-9]+)}/{proxied_path}
{base_url}/proxy/absolute/{port([0-9]+)}/{proxied_path}
{base_url}/{proxy_base}/{proxied_path}
'''
if 'Proxy-Connection' in self.request.headers:
del self.request.headers['Proxy-Connection']
self._record_activity()
if self.request.headers.get("Upgrade", "").lower() == 'websocket':
# We wanna websocket!
# jupyterhub/jupyter-server-proxy@36b3214
self.log.info("we wanna websocket, but we don't define WebSocketProxyHandler")
self.set_status(500)
body = self.request.body
if not body:
if self.request.method == 'POST':
body = b''
else:
body = None
client = httpclient.AsyncHTTPClient()
req = self._build_proxy_request(port, proxied_path, body)
response = await client.fetch(req, raise_error=False)
# record activity at start and end of requests
self._record_activity()
# For all non http errors...
if response.error and type(response.error) is not httpclient.HTTPError:
self.set_status(500)
self.write(str(response.error))
else:
self.set_status(response.code, response.reason)
# clear tornado default header
self._headers = httputil.HTTPHeaders()
for header, v in response.headers.get_all():
if header not in ('Content-Length', 'Transfer-Encoding',
'Content-Encoding', 'Connection'):
# some header appear multiple times, eg 'Set-Cookie'
self.add_header(header, v)
if response.body:
self.write(response.body)
def proxy_request_headers(self):
'''A dictionary of headers to be used when constructing
a tornado.httpclient.HTTPRequest instance for the proxy request.'''
return self.request.headers.copy()
def proxy_request_options(self):
'''A dictionary of options to be used when constructing
a tornado.httpclient.HTTPRequest instance for the proxy request.'''
return dict(follow_redirects=False)
# Support all the methods that torando does by default except for GET which
# is passed to WebSocketHandlerMixin and then to WebSocketHandler.
async def http_get(self, port, proxy_path=''):
'''Our non-websocket GET.'''
return await self.proxy(port, proxy_path)
def post(self, port, proxy_path=''):
return self.proxy(port, proxy_path)
def put(self, port, proxy_path=''):
return self.proxy(port, proxy_path)
def delete(self, port, proxy_path=''):
return self.proxy(port, proxy_path)
def head(self, port, proxy_path=''):
return self.proxy(port, proxy_path)
def patch(self, port, proxy_path=''):
return self.proxy(port, proxy_path)
def options(self, port, proxy_path=''):
return self.proxy(port, proxy_path)
def check_xsrf_cookie(self):
'''
http://www.tornadoweb.org/en/stable/guide/security.html
Defer to proxied apps.
'''
pass
def select_subprotocol(self, subprotocols):
'''Select a single Sec-WebSocket-Protocol during handshake.'''
if isinstance(subprotocols, list) and subprotocols:
self.log.info('Client sent subprotocols: {}'.format(subprotocols))
return subprotocols[0]
return super().select_subprotocol(subprotocols)
# FIXME: Move this to its own file. Too many packages now import this from nbrserverproxy.handlers
class SuperviseAndProxyHandler(LocalProxyHandler):
'''Manage a given process and requests to it '''
def __init__(self, *args, **kwargs):
self.requested_port = 0
super().__init__(*args, **kwargs)
def initialize(self, state):
self.state = state
if 'proc_lock' not in state:
state['proc_lock'] = Lock()
name = 'process'
@property
def port(self):
"""
Allocate either the requested port or a random empty port for use by
application
"""
if 'port' not in self.state:
sock = socket.socket()
sock.bind(('', self.requested_port))
self.state['port'] = sock.getsockname()[1]
sock.close()
return self.state['port']
def get_cwd(self):
"""Get the current working directory for our process
Override in subclass to launch the process in a directory
other than the current.
"""
return os.getcwd()
def get_env(self):
'''Set up extra environment variables for process. Typically
overridden in subclasses.'''
return {}
def get_timeout(self):
"""
Return timeout (in s) to wait before giving up on process readiness
"""
return 5
async def _http_ready_func(self, p):
url = 'http://localhost:{}'.format(self.port)
async with aiohttp.ClientSession() as session:
try:
async with session.get(url) as resp:
# We only care if we get back *any* response, not just 200
# If there's an error response, that can be shown directly to the user
self.log.debug('Got code {} back from {}'.format(resp.status, url))
return True
except aiohttp.ClientConnectionError:
self.log.debug('Connection to {} refused'.format(url))
return False
async def ensure_process(self):
"""
Start the process
"""
# We don't want multiple requests trying to start the process at the same time
# FIXME: Make sure this times out properly?
# Invariant here should be: when lock isn't being held, either 'proc' is in state &
# running, or not.
with (await self.state['proc_lock']):
if 'proc' not in self.state:
# FIXME: Prevent races here
# FIXME: Handle graceful exits of spawned processes here
cmd = self.get_cmd()
server_env = os.environ.copy()
# Set up extra environment variables for process
server_env.update(self.get_env())
timeout = self.get_timeout()
proc = SupervisedProcess(self.name, *cmd, env=server_env, ready_func=self._http_ready_func, ready_timeout=timeout, log=self.log)
self.state['proc'] = proc
try:
await proc.start()
is_ready = await proc.ready()
if not is_ready:
await proc.kill()
raise web.HTTPError(500, 'could not start {} in time'.format(self.name))
except:
# Make sure we remove proc from state in any error condition
del self.state['proc']
raise
@web.authenticated
async def proxy(self, port, path):
if not path.startswith('/'):
path = '/' + path
await self.ensure_process()
return await super().proxy(self.port, path)
async def http_get(self, path):
return await self.proxy(self.port, path)
async def open(self, path):
await self.ensure_process()
return await super().open(self.port, path)
def post(self, path):
return self.proxy(self.port, path)
def put(self, path):
return self.proxy(self.port, path)
def delete(self, path):
return self.proxy(self.port, path)
def head(self, path):
return self.proxy(self.port, path)
def patch(self, path):
return self.proxy(self.port, path)
def options(self, path):
return self.proxy(self.port, path)
def setup_handlers(web_app):
host_pattern = '.*$'
web_app.add_handlers('.*', [
(url_path_join(web_app.settings['base_url'], r'/proxy/(\d+)(.*)'),
LocalProxyHandler, {'absolute_url': False}),
(url_path_join(web_app.settings['base_url'], r'/proxy/absolute/(\d+)(.*)'),
LocalProxyHandler, {'absolute_url': True}),
])
# vim: set et ts=4 sw=4: