I have been trying to add some functionality to NavigaTor (written in python 2), which uses stem library to build TOR circuits. Basically, if a circuit fails, i am trying to build a new one with a new path (Navigator does not do that by default, and returns if the circuit fails). The relevant code is as follows:
Probe = namedtuple('Probe', 'path circs cbt streams perf bw')
def _circuit_handler(event):
""" Event handler for handling circuit states. """
if not event.build_flags or 'IS_INTERNAL' not in event.build_flags:
if event.id == self._cid:
probe.circs.append(event)
if self._circuit_built.is_set():
if event.status in ('FAILED', 'CLOSED'):
self._circuit_finished.set()
if not self._circuit_built.is_set():
if event.status in ('FAILED', 'BUILT'):
self._circuit_built.set()
elif event.status == 'LAUNCHED' and not self._cid:
self._cid = event.id
probe.circs.append(event)
self._manager.circ_launched.release()
In a while loop, I am trying to build circuits until a circuit has successfully been created:
while(true): #try until a valid circuit is received:
probe = Probe(path=self.path, circs=[], \
cbt=set(), streams=[],perf=[], bw=[])
circ_path = [node.desc.fingerprint for node in self.path] #Valid nodes already acquired and stored in path
self._manager.circ_launched.acquire()
self._controller.add_event_listener(_circuit_handler, EventType.CIRC)
self._controller.add_event_listener(_cbt_check, EventType.INFO)
circID = self._controller.extend_circuit(path=circ_path)
self._circuit_built.wait()
build_status = probe.circs[len(probe.circs) - 1].status
assert build_status == 'BUILT' or build_status == 'FAILED', \
'Wrong circuit status: %s.' % build_statusFirst
if build_status == 'FAILED':
self._controller.remove_event_listener(_circuit_handler)
self._controller.remove_event_listener(_cbt_check)
self.path = self._manager._get_new_path()
else:
break
Now, my problem is, that if the circuit is successful in the first attempt, this thing works fine. But if the build_status is FAILED, and loop runs again with a new valid path, the code crashes at the line:
build_status = probe.circs[len(probe.circs) - 1].status
With IndexError: list index out of range. Upon debugging, I have observed that the probe.circs remains empty, even though the _circuit_handler event is supposed to append to it. This happens every single time for the second circuit, even though it works fine if the first circuit was successful. What am I doing wrong here?
