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# coding=utf-8
import ast
from fcntl import fcntl, F_GETFL, F_SETFL
import io
import multiprocessing
import os
import queue
import signal
import subprocess
import sys
import threading
import time
import server.user_session
from db.models import Problem
from . import problems
__all__ = ['PythonSession']
class PythonSession(object):
"""Abstracts a Python session.
Only public methods are available to the outside world due to the use of multiprocessing managers.
Therefore prefix any private methods with an underscore (_).
No properties are accessible; use getters and setters instead.
Values are passed by value instead of by reference (deep copy!).
"""
def __init__(self, output_cb=None):
self._access_lock = threading.Lock()
self._sent_hints = []
self._control = queue.Queue()
self._interpreter = threading.Thread(target=_interpreter,
kwargs={'control': self._control, 'callback': output_cb})
self._interpreter.start()
def run(self, code=None, inputs=None, timeout=1.0):
# Launch processes.
futures = []
for expr, stdin in inputs:
conn_parent, conn_child = multiprocessing.Pipe()
p = multiprocessing.Process(target=_run_exec, args=(conn_child, code, expr, stdin))
p.start()
futures.append((p, conn_parent))
# Wait for results.
results = []
start = time.monotonic()
for p, conn in futures:
now = time.monotonic()
real_timeout = max(0, timeout - (now - start))
if conn.poll(real_timeout):
results.append(conn.recv())
else:
results.append((None, None, None, 'timed out'))
p.terminate()
return results
def exec(self, program):
self._control.put_nowait(('exec', program))
def push(self, stdin):
self._control.put_nowait(('push', stdin))
def stop(self):
self._control.put_nowait(('stop', None))
def destroy(self):
self._control.put_nowait(('done', None))
def __del__(self):
self.destroy()
def hint(self, sid, problem_id, program):
language, problem_group, problem = Problem.get_identifier(problem_id)
language_module = problems.load_language(language, 'common')
problem_module = problems.load_problem(language, problem_group, problem, 'common')
hints = []
if hasattr(language_module, 'hint'):
hints = language_module.hint(self.run, program)
if not hints and hasattr(problem_module, 'hint'):
hints = problem_module.hint(self.run, program)
if not hints:
hints = [{'id': 'no_hint'}]
self._instantiate_and_save_hints(language_module, problem_module, hints)
return hints
def test(self, sid, problem_id, program):
language, problem_group, problem = Problem.get_identifier(problem_id)
language_module = problems.load_language(language, 'common')
problem_module = problems.load_problem(language, problem_group, problem, 'common')
try:
passed, hints = problem_module.test(self.run, program)
except AttributeError as ex:
hints = [{'id': 'system_error', 'args': {'message': 'test function does not exist'}}]
self._instantiate_and_save_hints(language_module, problem_module, hints)
return hints
# Add hint parameters (such as message index) based on hint class. Append
# the finalized hints to the list of sent hints.
def _instantiate_and_save_hints(self, language_mod, problem_mod, hints):
with self._access_lock:
for hint in hints:
for mod in [language_mod, problem_mod]:
if hasattr(mod, 'hint_type') and hint['id'] in mod.hint_type:
hint_type = mod.hint_type[hint['id']]
hint_type.instantiate(hint, self._sent_hints)
self._sent_hints.extend(hints)
def _interpreter(control, callback):
directory = os.path.dirname(os.path.realpath(__file__))
# TODO drop privileges using a wrapper
script = os.path.join(directory, '..', 'python', 'interpreter.py')
proc = None
while True:
# Ensure the interpreter process is running.
if proc is None:
proc = subprocess.Popen([script],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT)
# Set the non-blocking flag for stdout.
flags = fcntl(proc.stdout.fileno(), F_GETFL)
fcntl(proc.stdout.fileno(), F_SETFL, flags | os.O_NONBLOCK)
# Get a control command.
try:
cmd, data = control.get_nowait()
if cmd == 'exec':
exec_str = 'exec("""\\\n{}\n""")\n'.format(data.replace('"', '\\"'))
proc.stdin.write(exec_str.encode('utf-8'))
proc.stdin.flush()
elif cmd == 'push':
proc.stdin.write(data.encode('utf-8'))
proc.stdin.flush()
elif cmd == 'stop':
proc.send_signal(signal.SIGINT)
elif cmd == 'done':
break
except:
pass
# Communicate with child process.
retcode = proc.poll()
if retcode is None:
data = proc.stdout.read()
if data:
if len(data) > 20000:
proc.kill()
proc = None
callback('Child killed for talking too much.\n')
else:
# NOTE this might fail if read() stops in the middle of utf8 sequence
text = data.decode('utf-8')
if text:
callback(text)
else:
if retcode == -9: # killed by ulimit
callback('Child killed due to overconsumption.\n')
elif retcode == -31: # killed by seccomp
callback('Child killed due to sandbox misbehavior.\n')
else:
callback('Child exited with status "{}".\n'.format(retcode))
proc = None
# TODO we should select() on control and proc.stdout instead of polling
time.sleep(0.1)
# We are done, kill the child.
if proc is not None:
proc.kill()
# Execute [code] and evaluate [expr]. Input is given by the string [stdin].
# Return result of evaluation, the contents of stdout and stderr, and the
# exception traceback.
# TODO sandbox this
def _run_exec(conn, code, expr=None, stdin=''):
result, out, err, exc = None, None, None, None
sys.stdin = io.StringIO(stdin)
sys.stdout = io.StringIO()
sys.stderr = io.StringIO()
try:
env = {}
if code:
exec(code, env)
if expr:
result = eval(expr, env)
except Exception as ex:
# Exception is not JSON serializable, so return traceback as string
# (without the first entry, which is this function).
import traceback
e_type, e_value, e_tb = sys.exc_info()
stack = traceback.extract_tb(e_tb)
exc = ''.join(
['Traceback (most recent call last):\n'] +
[' line {}, in {}\n'.format(lineno, name) + (line+'\n' if line else '')
for filename, lineno, name, line in stack[1:]] +
traceback.format_exception_only(e_type, e_value)
).rstrip()
finally:
out = sys.stdout.getvalue()
err = sys.stderr.getvalue()
sys.stdin.close()
sys.stdout.close()
sys.stderr.close()
conn.send((result, out, err, exc))
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