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#!/usr/bin/env python
# encoding: utf-8
import json
import threading
import time
from twisted.internet import defer, reactor, threads
import zmq
from zmq.auth.thread import ThreadAuthenticator
from leap.bitmask.backend.api import API
from leap.bitmask.backend.utils import get_backend_certificates
from leap.bitmask.backend.signaler import Signaler
import logging
logger = logging.getLogger(__name__)
class Backend(object):
"""
Backend server.
Receives signals from backend_proxy and emit signals if needed.
"""
PORT = '5556'
BIND_ADDR = "tcp://127.0.0.1:%s" % PORT
def __init__(self):
"""
Backend constructor, create needed instances.
"""
self._signaler = Signaler()
self._do_work = threading.Event() # used to stop the worker thread.
self._zmq_socket = None
self._ongoing_defers = []
self._init_zmq()
def _init_zmq(self):
"""
Configure the zmq components and connection.
"""
context = zmq.Context()
socket = context.socket(zmq.REP)
# Start an authenticator for this context.
auth = ThreadAuthenticator(context)
auth.start()
auth.allow('127.0.0.1')
# Tell authenticator to use the certificate in a directory
auth.configure_curve(domain='*', location=zmq.auth.CURVE_ALLOW_ANY)
public, secret = get_backend_certificates()
socket.curve_publickey = public
socket.curve_secretkey = secret
socket.curve_server = True # must come before bind
socket.bind(self.BIND_ADDR)
self._zmq_socket = socket
def _worker(self):
"""
Receive requests and send it to process.
Note: we use a simple while since is less resource consuming than a
Twisted's LoopingCall.
"""
while self._do_work.is_set():
# Wait for next request from client
try:
request = self._zmq_socket.recv(zmq.NOBLOCK)
self._zmq_socket.send("OK")
logger.debug("Received request: '{0}'".format(request))
self._process_request(request)
except zmq.ZMQError as e:
if e.errno != zmq.EAGAIN:
raise
time.sleep(0.01)
def _stop_reactor(self):
"""
Stop the Twisted reactor, but first wait a little for some threads to
complete their work.
Note: this method needs to be run in a different thread so the
time.sleep() does not block and other threads can finish.
i.e.:
use threads.deferToThread(this_method) instead of this_method()
"""
wait_max = 5 # seconds
wait_step = 0.5
wait = 0
while self._ongoing_defers and wait < wait_max:
time.sleep(wait_step)
wait += wait_step
msg = "Waiting for running threads to finish... {0}/{1}"
msg = msg.format(wait, wait_max)
logger.debug(msg)
# after a timeout we shut down the existing threads.
for d in self._ongoing_defers:
d.cancel()
reactor.stop()
logger.debug("Twisted reactor stopped.")
def run(self):
"""
Start the ZMQ server and run the loop to handle requests.
"""
self._signaler.start()
self._do_work.set()
threads.deferToThread(self._worker)
reactor.run()
def stop(self):
"""
Stop the server and the zmq request parse loop.
"""
logger.debug("STOP received.")
self._signaler.stop()
self._do_work.clear()
threads.deferToThread(self._stop_reactor)
def _process_request(self, request_json):
"""
Process a request and call the according method with the given
parameters.
:param request_json: a json specification of a request.
:type request_json: str
"""
try:
# request = zmq.utils.jsonapi.loads(request_json)
# We use stdlib's json to ensure that we get unicode strings
request = json.loads(request_json)
api_method = request['api_method']
kwargs = request['arguments'] or None
except Exception as e:
msg = "Malformed JSON data in Backend request '{0}'. Exc: {1!r}"
msg = msg.format(request_json, e)
msg = msg.format(request_json)
logger.critical(msg)
raise
if api_method not in API:
logger.error("Invalid API call '{0}'".format(api_method))
return
self._run_in_thread(api_method, kwargs)
def _run_in_thread(self, api_method, kwargs):
"""
Run the method name in a thread with the given arguments.
:param api_method: the callable name to run in a thread.
:type api_method: str
:param kwargs: the arguments dict that will be sent to the callable.
:type kwargs: tuple
"""
func = getattr(self, api_method)
method = func
if kwargs is not None:
method = lambda: func(**kwargs)
logger.debug("Running method: '{0}' "
"with args: '{1}' in a thread".format(api_method, kwargs))
# run the action in a thread and keep track of it
d = threads.deferToThread(method)
d.addCallback(self._done_action, d)
d.addErrback(self._done_action, d)
self._ongoing_defers.append(d)
def _done_action(self, failure, d):
"""
Remove the defer from the ongoing list.
:param failure: the failure that triggered the errback.
None if no error.
:type failure: twisted.python.failure.Failure
:param d: defer to remove
:type d: twisted.internet.defer.Deferred
"""
if failure is not None:
if failure.check(defer.CancelledError):
logger.debug("A defer was cancelled.")
else:
logger.error("There was a failure - {0!r}".format(failure))
logger.error(failure.getTraceback())
if d in self._ongoing_defers:
self._ongoing_defers.remove(d)
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