#!/usr/bin/env python """This server runs an HTTP server (using tornado) to which code can be submitted for checking. This is asynchronous so once submitted the user can check for the result. It *should* be run as root and will run as the user 'nobody' so as to minimize any damange by errant code. This can be configured by editing settings.py to run as many servers as desired. """ # Standard library imports from __future__ import unicode_literals from argparse import ArgumentParser import json from multiprocessing import Process, Queue, Manager import os from os.path import dirname, abspath import pwd import sys import time # Library imports import requests from tornado.ioloop import IOLoop from tornado.web import Application, RequestHandler import urllib # Local imports from .settings import N_CODE_SERVERS, SERVER_POOL_PORT from .grader import Grader MY_DIR = abspath(dirname(__file__)) # Private Protocol ########## def run_as_nobody(): """Runs the current process as nobody.""" # Set the effective uid and to that of nobody. nobody = pwd.getpwnam('nobody') os.setegid(nobody.pw_gid) os.seteuid(nobody.pw_uid) def check_code(pid, job_queue, results): """Check the code, this runs forever. """ while True: uid, json_data, user_dir = job_queue.get(True) results[uid] = dict(status='running', pid=pid, result=None) data = json.loads(json_data) grader = Grader(user_dir) result = grader.evaluate(data) results[uid] = dict(status='done', result=json.dumps(result)) ############################################################################### # `ServerPool` class. ############################################################################### class ServerPool(object): """Manages a pool of processes checking code.""" def __init__(self, n, pool_port=50000): """Create a pool of servers. Parameters ---------- n : int Number of code servers to run pool_port : int Port at which the server pool should serve. """ self.n = n self.manager = Manager() self.results = self.manager.dict() self.my_port = pool_port self.job_queue = Queue() processes = [] for i in range(n): p = self._make_process(i) processes.append(p) self.processes = processes self.app = self._make_app() def _make_app(self): app = Application([ (r"/.*", MainHandler, dict(server=self)), ]) app.listen(self.my_port) return app def _make_process(self, pid): return Process( target=check_code, args=(pid, self.job_queue, self.results) ) def _start_code_servers(self): for proc in self.processes: if proc.pid is None: proc.start() def _handle_dead_process(self, result): if result.get('status') == 'running': pid = result.get('pid') proc = self.processes[pid] if not proc.is_alive(): # If the processes is dead, something bad happened so # restart that process. new_proc = self._make_process(pid) self.processes[pid] = new_proc new_proc.start() result['status'] = 'done' result['result'] = json.dumps(dict( success=False, weight=0.0, error=['Process ended with exit code %s.' % proc.exitcode] )) # Public Protocol ########## def get_status(self): """Returns current job queue size, total number of processes alive. """ qs = sum(r['status'] == 'not started' for r in self.results.values()) alive = sum(p.is_alive() for p in self.processes) n_running = sum(r['status'] == 'running' for r in self.results.values()) return qs, alive, n_running def submit(self, uid, json_data, user_dir): self.results[uid] = dict(status='not started') self.job_queue.put((uid, json_data, user_dir)) def get_result(self, uid): result = self.results.get(uid, dict(status='unknown')) self._handle_dead_process(result) if result.get('status') == 'done': self.results.pop(uid) return json.dumps(result) def run(self): """Run server which returns an available server port where code can be executed. """ # We start the code servers here to ensure they are run as nobody. self._start_code_servers() IOLoop.current().start() def stop(self): """Stop all the code server processes. """ for proc in self.processes: proc.terminate() IOLoop.current().stop() class MainHandler(RequestHandler): def initialize(self, server): self.server = server def get(self): path = self.request.path[1:] if len(path) == 0: q_size, alive, running = self.server.get_status() result = "%d processes, %d running, %d queued" % ( alive, running, q_size ) self.write(result) else: uid = path json_result = self.server.get_result(uid) self.write(json_result) def post(self): uid = self.get_argument('uid') json_data = self.get_argument('json_data') user_dir = self.get_argument('user_dir') self.server.submit(uid, json_data, user_dir) self.write('OK') def submit(url, uid, json_data, user_dir): '''Submit a job to the code server. Parameters ---------- url : str URL of the server pool. uid : str Unique ID of the submission. json_data : jsonized str Data to send to the code checker. user_dir : str User directory. ''' requests.post( url, data=dict(uid=uid, json_data=json_data, user_dir=user_dir) ) def get_result(url, uid, block=False): '''Get the status of a job submitted to the code server. Returns the result currently known in the form of a dict. The dictionary contains two keys, 'status' and 'result'. The status can be one of ['running', 'not started', 'done', 'unknown']. The result is the result of the code execution as a jsonized string. Parameters ---------- url : str URL of the server pool. uid : str Unique ID of the submission. block : bool Set to True if you wish to block till result is done. ''' def _get_data(): r = requests.get(urllib.parse.urljoin(url, str(uid))) return json.loads(r.content.decode('utf-8')) data = _get_data() if block: while data.get('status') != 'done': time.sleep(0.1) data = _get_data() return data ############################################################################### def main(args=None): parser = ArgumentParser(description=__doc__) parser.add_argument( 'n', nargs='?', type=int, default=N_CODE_SERVERS, help="Number of servers to run." ) parser.add_argument( '-p', '--port', dest='port', default=SERVER_POOL_PORT, help="Port at which the http server should run." ) options = parser.parse_args(args) # Called before serverpool is created so that the multiprocessing # can work properly. run_as_nobody() server_pool = ServerPool(n=options.n, pool_port=options.port) server_pool.run() if __name__ == '__main__': args = sys.argv[1:] main(args)