#!/usr/bin/env python
"""This server runs an XMLRPC server that can be submitted code and tests
and returns the output. 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. One can also
specify the ports on the command line. Here are examples::
$ sudo ./code_server.py
# Runs servers based on settings.py:SERVER_PORTS one server per port given.
or::
$ sudo ./code_server.py 8001 8002 8003 8004 8005
# Runs 5 servers on ports specified.
All these servers should be running as nobody. This will also start a server
pool that defaults to port 50000 and is configurable in
settings.py:SERVER_POOL_PORT. This port exposes a `get_server_port` function
that returns an available server.
"""
import sys
import traceback
from SimpleXMLRPCServer import SimpleXMLRPCServer
import pwd
import os
import stat
from os.path import isdir, dirname, abspath, join, isfile
import signal
from multiprocessing import Process, Queue
import subprocess
import re
# Local imports.
from settings import SERVER_PORTS, SERVER_TIMEOUT, SERVER_POOL_PORT
MY_DIR = abspath(dirname(__file__))
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)
# Raised when the code times-out.
# c.f. http://pguides.net/python/timeout-a-function
class TimeoutException(Exception):
pass
def timeout_handler(signum, frame):
"""A handler for the ALARM signal."""
raise TimeoutException('Code took too long to run.')
###############################################################################
# `CodeServer` class.
###############################################################################
class CodeServer(object):
"""A code server that executes user submitted test code, tests it and
reports if the code was correct or not.
"""
def __init__(self, port, queue):
self.port = port
self.queue = queue
msg = 'Code took more than %s seconds to run. You probably '\
'have an infinite loop in your code.' % SERVER_TIMEOUT
self.timeout_msg = msg
def run_python_code(self, answer, test_code, in_dir=None):
"""Tests given Python function (`answer`) with the `test_code`
supplied. If the optional `in_dir` keyword argument is supplied
it changes the directory to that directory (it does not change
it back to the original when done). This function also timesout
when the function takes more than SERVER_TIMEOUT seconds to run
to prevent runaway code.
Returns
-------
A tuple: (success, error message).
"""
if in_dir is not None and isdir(in_dir):
os.chdir(in_dir)
# Add a new signal handler for the execution of this code.
old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(SERVER_TIMEOUT)
success = False
tb = None
try:
submitted = compile(answer, '<string>', mode='exec')
g = {}
exec submitted in g
_tests = compile(test_code, '<string>', mode='exec')
exec _tests in g
except TimeoutException:
err = self.timeout_msg
except AssertionError:
type, value, tb = sys.exc_info()
info = traceback.extract_tb(tb)
fname, lineno, func, text = info[-1]
text = str(test_code).splitlines()[lineno-1]
err = "{0} {1} in: {2}".format(type.__name__, str(value), text)
except:
type, value = sys.exc_info()[:2]
err = "Error: {0}".format(repr(value))
else:
success = True
err = 'Correct answer'
finally:
del tb
# Set back any original signal handler.
signal.signal(signal.SIGALRM, old_handler)
# Cancel the signal if any, see signal.alarm documentation.
signal.alarm(0)
# Put us back into the server pool queue since we are free now.
self.queue.put(self.port)
return success, err
def run_bash_code(self, answer, test_code, in_dir=None):
"""Tests given Bash code (`answer`) with the `test_code` supplied.
The testcode should typically contain two lines, the first is a path to
the reference script we are to compare against. The second is a path
to the arguments to be supplied to the reference and submitted script.
The output of these will be compared for correctness.
If the path's start with a "/" then we assume they are absolute paths.
If not, we assume they are relative paths w.r.t. the location of this
code_server script.
If the optional `in_dir` keyword argument is supplied it changes the
directory to that directory (it does not change it back to the original
when done).
Returns
-------
A tuple: (success, error message).
"""
if in_dir is not None and isdir(in_dir):
os.chdir(in_dir)
def _set_exec(fname):
os.chmod(fname, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR
| stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP
| stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH)
submit_f = open('submit.sh', 'w')
submit_f.write(answer.lstrip())
submit_f.close()
submit_path = abspath(submit_f.name)
_set_exec(submit_path)
ref_path, test_case_path = test_code.strip().splitlines()
if not ref_path.startswith('/'):
ref_path = join(MY_DIR, ref_path)
if not test_case_path.startswith('/'):
test_case_path = join(MY_DIR, test_case_path)
# Add a new signal handler for the execution of this code.
old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(SERVER_TIMEOUT)
# Do whatever testing needed.
success = False
try:
success, err = self.check_bash_script(ref_path, submit_path,
test_case_path)
except TimeoutException:
err = self.timeout_msg
except:
type, value = sys.exc_info()[:2]
err = "Error: {0}".format(repr(value))
finally:
# Set back any original signal handler.
signal.signal(signal.SIGALRM, old_handler)
# Delete the created file.
os.remove(submit_path)
# Cancel the signal if any, see signal.alarm documentation.
signal.alarm(0)
# Put us back into the server pool queue since we are free now.
self.queue.put(self.port)
return success, err
def _run_command(self, cmd_args, *args, **kw):
"""Run a command in a subprocess while blocking, the process is killed
if it takes more than 2 seconds to run. Return the Popen object, the
stdout and stderr.
"""
try:
proc = subprocess.Popen(cmd_args, *args, **kw)
stdout, stderr = proc.communicate()
except TimeoutException:
# Runaway code, so kill it.
proc.kill()
# Re-raise exception.
raise
return proc, stdout, stderr
def check_bash_script(self, ref_script_path, submit_script_path,
test_case_path=None):
""" Function validates student script using instructor script as
reference. Test cases can optionally be provided. The first argument
ref_script_path, is the path to instructor script, it is assumed to
have executable permission. The second argument submit_script_path, is
the path to the student script, it is assumed to have executable
permission. The Third optional argument is the path to test the
scripts. Each line in this file is a test case and each test case is
passed to the script as standard arguments.
Returns
--------
returns (True, "Correct answer") : If the student script passes all
test cases/have same output, when compared to the instructor script
returns (False, error_msg): If the student script fails a single
test/have dissimilar output, when compared to the instructor script.
Returns (False, error_msg): If mandatory arguments are not files or if
the required permissions are not given to the file(s).
"""
if not isfile(ref_script_path):
return False, "No file at %s" % ref_script_path
if not isfile(submit_script_path):
return False, 'No file at %s' % submit_script_path
if not os.access(ref_script_path, os.X_OK):
return False, 'Script %s is not executable' % ref_script_path
if not os.access(submit_script_path, os.X_OK):
return False, 'Script %s is not executable' % submit_script_path
if test_case_path is None:
ret = self._run_command(ref_script_path, stdin=None,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, inst_stdout, inst_stderr = ret
ret = self._run_command(submit_script_path, stdin=None,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, stdnt_stdout, stdnt_stderr = ret
if inst_stdout == stdnt_stdout:
return True, 'Correct answer'
else:
err = "Error: expected %s, got %s" % (inst_stderr,
stdnt_stderr)
return False, err
else:
if not isfile(test_case_path):
return False, "No test case at %s" % test_case_path
if not os.access(ref_script_path, os.R_OK):
return False, "Test script %s, not readable" % test_case_path
valid_answer = True # We initially make it one, so that we can
# stop once a test case fails
loop_count = 0 # Loop count has to be greater than or
# equal to one.
# Useful for caching things like empty
# test files,etc.
test_cases = open(test_case_path).readlines()
num_lines = len(test_cases)
for test_case in test_cases:
loop_count += 1
if valid_answer:
args = [ref_script_path] + [x for x in test_case.split()]
ret = self._run_command(args, stdin=None,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, inst_stdout, inst_stderr = ret
args = [submit_script_path]+[x for x in test_case.split()]
ret = self._run_command(args, stdin=None,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, stdnt_stdout, stdnt_stderr = ret
valid_answer = inst_stdout == stdnt_stdout
if valid_answer and (num_lines == loop_count):
return True, "Correct answer"
else:
err = "Error:expected %s, got %s" % (inst_stdout+inst_stderr,
stdnt_stdout+stdnt_stderr)
return False, err
def run_c_code(self, answer, test_code, in_dir=None):
"""Tests given C code (`answer`) with the `test_code` supplied.
The testcode is a path to the reference code.
The reference code will call the function submitted by the student.
The reference code will check for the expected output.
If the path's start with a "/" then we assume they are absolute paths.
If not, we assume they are relative paths w.r.t. the location of this
code_server script.
If the optional `in_dir` keyword argument is supplied it changes the
directory to that directory (it does not change it back to the original
when done).
Returns
-------
A tuple: (success, error message).
"""
if in_dir is not None and isdir(in_dir):
os.chdir(in_dir)
# File extension must be .c
submit_f = open('submit.c', 'w')
submit_f.write(answer.lstrip())
submit_f.close()
submit_path = abspath(submit_f.name)
ref_path = test_code.strip()
if not ref_path.startswith('/'):
ref_path = join(MY_DIR, ref_path)
# Add a new signal handler for the execution of this code.
old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(SERVER_TIMEOUT)
# Do whatever testing needed.
success = False
try:
success, err = self._check_c_cpp_code(ref_path, submit_path)
except TimeoutException:
err = self.timeout_msg
except:
type, value = sys.exc_info()[:2]
err = "Error: {0}".format(repr(value))
finally:
# Set back any original signal handler.
signal.signal(signal.SIGALRM, old_handler)
# Delete the created file.
os.remove(submit_path)
# Cancel the signal if any, see signal.alarm documentation.
signal.alarm(0)
# Put us back into the server pool queue since we are free now.
self.queue.put(self.port)
return success, err
def _compile_command(self, cmd, *args, **kw):
"""Compiles C/C++/java code and returns errors if any.
Run a command in a subprocess while blocking, the process is killed
if it takes more than 2 seconds to run. Return the Popen object, the
stderr.
"""
try:
proc_compile = subprocess.Popen(cmd, shell=True, stdin=None,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
out, err = proc_compile.communicate()
except TimeoutException:
# Runaway code, so kill it.
proc_compile.kill()
# Re-raise exception.
raise
return proc_compile, err
def _check_c_cpp_code(self, ref_code_path, submit_code_path):
""" Function validates student code using instructor code as
reference.The first argument ref_code_path, is the path to
instructor code, it is assumed to have executable permission.
The second argument submit_code_path, is the path to the student
code, it is assumed to have executable permission.
Returns
--------
returns (True, "Correct answer") : If the student function returns
expected output when called by reference code.
returns (False, error_msg): If the student function fails to return
expected output when called by reference code.
Returns (False, error_msg): If mandatory arguments are not files or
if the required permissions are not given to the file(s).
"""
if not isfile(ref_code_path):
return False, "No file at %s" % ref_code_path
if not isfile(submit_code_path):
return False, 'No file at %s' % submit_code_path
success = False
output_path = os.getcwd() + '/output'
compile_command = "g++ %s -c -o %s" % (submit_code_path, output_path)
ret = self._compile_command(compile_command)
proc, stdnt_stderr = ret
# Only if compilation is successful, the program is executed
# And tested with testcases
if stdnt_stderr == '':
executable = os.getcwd() + '/executable'
compile_main = "g++ %s %s -o %s" % (ref_code_path, output_path,
executable)
ret = self._compile_command(compile_main)
proc, main_err = ret
if main_err == '':
args = [executable]
ret = self._run_command(args, stdin=None,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, stdout, stderr = ret
if proc.returncode == 0:
success, err = True, "Correct answer"
else:
err = stdout + "\n" + stderr
os.remove(executable)
else:
err = "Error:"
try:
error_lines = main_err.splitlines()
for e in error_lines:
err = err + "\n" + e.split(":", 1)[1]
except:
err = err + "\n" + main_err
os.remove(output_path)
else:
err = "Compilation Error:"
try:
error_lines = stdnt_stderr.splitlines()
for e in error_lines:
if ':' in e:
err = err + "\n" + e.split(":", 1)[1]
else:
err = err + "\n" + e
except:
err = err + "\n" + stdnt_stderr
return success, err
def run_cplus_code(self, answer, test_code, in_dir=None):
"""Tests given C++ code (`answer`) with the `test_code` supplied.
The testcode is a path to the reference code.
The reference code will call the function submitted by the student.
The reference code will check for the expected output.
If the path's start with a "/" then we assume they are absolute paths.
If not, we assume they are relative paths w.r.t. the location of this
code_server script.
If the optional `in_dir` keyword argument is supplied it changes the
directory to that directory (it does not change it back to the original
when done).
Returns
-------
A tuple: (success, error message).
"""
if in_dir is not None and isdir(in_dir):
os.chdir(in_dir)
# The file extension must be .cpp
submit_f = open('submitstd.cpp', 'w')
submit_f.write(answer.lstrip())
submit_f.close()
submit_path = abspath(submit_f.name)
ref_path = test_code.strip()
if not ref_path.startswith('/'):
ref_path = join(MY_DIR, ref_path)
# Add a new signal handler for the execution of this code.
old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(SERVER_TIMEOUT)
# Do whatever testing needed.
success = False
try:
success, err = self._check_c_cpp_code(ref_path, submit_path)
except TimeoutException:
err = self.timeout_msg
except:
type, value = sys.exc_info()[:2]
err = "Error: {0}".format(repr(value))
finally:
# Set back any original signal handler.
signal.signal(signal.SIGALRM, old_handler)
# Delete the created file.
os.remove(submit_path)
# Cancel the signal if any, see signal.alarm documentation.
signal.alarm(0)
# Put us back into the server pool queue since we are free now.
self.queue.put(self.port)
return success, err
def run_java_code(self, answer, test_code, in_dir=None):
"""Tests given java code (`answer`) with the `test_code` supplied.
The testcode is a path to the reference code.
The reference code will call the function submitted by the student.
The reference code will check for the expected output.
If the path's start with a "/" then we assume they are absolute paths.
If not, we assume they are relative paths w.r.t. the location of this
code_server script.
If the optional `in_dir` keyword argument is supplied it changes the
directory to that directory (it does not change it back to the original
when done).
Returns
-------
A tuple: (success, error message).
"""
if in_dir is not None and isdir(in_dir):
os.chdir(in_dir)
# The file extension must be .java
# The class name and file name must be same in java
submit_f = open('Test.java', 'w')
submit_f.write(answer.lstrip())
submit_f.close()
submit_path = abspath(submit_f.name)
ref_path = test_code.strip()
if not ref_path.startswith('/'):
ref_path = join(MY_DIR, ref_path)
# Add a new signal handler for the execution of this code.
old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(SERVER_TIMEOUT)
# Do whatever testing needed.
success = False
try:
success, err = self._check_java_code(ref_path, submit_path)
except TimeoutException:
err = self.timeout_msg
except:
type, value = sys.exc_info()[:2]
err = "Error: {0}".format(repr(value))
finally:
# Set back any original signal handler.
signal.signal(signal.SIGALRM, old_handler)
# Delete the created file.
os.remove(submit_path)
# Cancel the signal if any, see signal.alarm documentation.
signal.alarm(0)
# Put us back into the server pool queue since we are free now.
self.queue.put(self.port)
return success, err
def _check_java_code(self, ref_code_path, submit_code_path):
""" Function validates student code using instructor code as
reference.The first argument ref_code_path, is the path to
instructor code, it is assumed to have executable permission.
The second argument submit_code_path, is the path to the student
code, it is assumed to have executable permission.
Returns
--------
returns (True, "Correct answer") : If the student function returns
expected output when called by reference code.
returns (False, error_msg): If the student function fails to return
expected output when called by reference code.
Returns (False, error_msg): If mandatory arguments are not files or
if the required permissions are not given to the file(s).
"""
if not isfile(ref_code_path):
return False, "No file at %s" % ref_code_path
if not isfile(submit_code_path):
return False, 'No file at %s' % submit_code_path
success = False
compile_command = "javac %s" % (submit_code_path)
ret = self._compile_command(compile_command)
proc, stdnt_stderr = ret
stdnt_stderr = self._remove_null_substitute_char(stdnt_stderr)
# Only if compilation is successful, the program is executed
# And tested with testcases
if stdnt_stderr == '':
student_directory = os.getcwd() + '/'
student_file_name = "Test"
compile_main = "javac %s -classpath %s -d %s" % (ref_code_path,
student_directory,
student_directory)
ret = self._compile_command(compile_main)
proc, main_err = ret
main_err = self._remove_null_substitute_char(main_err)
if main_err == '':
main_file_name = (ref_code_path.split('/')[-1]).split('.')[0]
run_command = "java -cp %s %s" % (student_directory,
main_file_name)
ret = self._run_command(run_command,
stdin=None,
shell=True,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, stdout, stderr = ret
if proc.returncode == 0:
success, err = True, "Correct answer"
else:
err = stdout + "\n" + stderr
success = False
os.remove("%s%s.class" % (student_directory, main_file_name))
else:
err = "Error:\n"
try:
error_lines = main_err.splitlines()
for e in error_lines:
if ':' in e:
err = err + "\n" + e.split(":", 1)[1]
else:
err = err + "\n" + e
except:
err = err + "\n" + main_err
os.remove("%s%s.class" % (student_directory, student_file_name))
else:
err = "Compilation Error:\n"
try:
error_lines = stdnt_stderr.splitlines()
for e in error_lines:
if ':' in e:
err = err + "\n" + e.split(":", 1)[1]
else:
err = err + "\n" + e
except:
err = err + "\n" + stdnt_stderr
return success, err
def _remove_null_substitute_char(self, string):
"""Returns a string without any null and substitute characters"""
stripped = ""
for c in string:
if ord(c) is not 26 and ord(c) is not 0:
stripped = stripped + c
return ''.join(stripped)
def run_scilab_code(self, answer, test_code, in_dir=None):
"""Tests given Scilab function (`answer`) with the `test_code`
supplied. If the optional `in_dir` keyword argument is supplied
it changes the directory to that directory (it does not change
it back to the original when done). This function also timesout
when the function takes more than SERVER_TIMEOUT seconds to run
to prevent runaway code.
The testcode is a path to the reference code.
The reference code will call the function submitted by the student.
The reference code will check for the expected output.
If the path's start with a "/" then we assume they are absolute paths.
If not, we assume they are relative paths w.r.t. the location of this
code_server script.
Returns
-------
A tuple: (success, error message).
"""
if in_dir is not None and isdir(in_dir):
os.chdir(in_dir)
# Removes all the commands that terminates scilab
answer,i = self._remove_scilab_exit(answer.lstrip())
# Throw message if there are commmands that terminates scilab
add_err=""
if i > 0:
add_err = "Please do not use exit, quit and abort commands in your\
code.\n Otherwise your code will not be evaluated\
correctly.\n"
# The file extension should be .sci
submit_f = open('function.sci','w')
submit_f.write(answer)
submit_f.close()
submit_path = abspath(submit_f.name)
ref_path = test_code.strip()
if not ref_path.startswith('/'):
ref_path = join(MY_DIR, ref_path)
# Add a new signal handler for the execution of this code.
old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(SERVER_TIMEOUT)
# Do whatever testing needed.
success = False
try:
cmd = 'printf "lines(0)\nexec(\'{0}\',2);\nquit();"'.format(ref_path)
cmd += ' | timeout 8 scilab-cli -nb'
ret = self._run_command(cmd,
shell=True,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc, stdout, stderr = ret
# Get only the error.
stderr = self._get_error(stdout)
if stderr is None:
# Clean output
stdout = self._strip_output(stdout)
if proc.returncode == 5:
success, err = True, "Correct answer"
else:
err = add_err + stdout
else:
err = add_err + stderr
except TimeoutException:
err = self.timeout_msg
except:
type, value = sys.exc_info()[:2]
err = "Error: {0}".format(repr(value))
finally:
# Set back any original signal handler.
signal.signal(signal.SIGALRM, old_handler)
# Delete the created file.
os.remove(submit_path)
# Cancel the signal if any, see signal.alarm documentation.
signal.alarm(0)
# Put us back into the server pool queue since we are free now.
self.queue.put(self.port)
return success, err
def _remove_scilab_exit(self, string):
"""
Removes exit, quit and abort from the scilab code
"""
new_string = ""
i=0
for line in string.splitlines():
new_line = re.sub(r"exit.*$","",line)
new_line = re.sub(r"quit.*$","",new_line)
new_line = re.sub(r"abort.*$","",new_line)
if line != new_line:
i=i+1
new_string = new_string +'\n'+ new_line
return new_string, i
def _get_error(self, string):
"""
Fetches only the error from the string.
Returns None if no error.
"""
obj = re.search("!.+\n.+",string);
if obj:
return obj.group()
return None
def _strip_output(self, out):
"""
Cleans whitespace from the output
"""
strip_out = "Message"
for l in out.split('\n'):
if l.strip():
strip_out = strip_out+"\n"+l.strip()
return strip_out
def run(self):
"""Run XMLRPC server, serving our methods.
"""
server = SimpleXMLRPCServer(("localhost", self.port))
self.server = server
server.register_instance(self)
self.queue.put(self.port)
server.serve_forever()
###############################################################################
# `ServerPool` class.
###############################################################################
class ServerPool(object):
"""Manages a pool of CodeServer objects."""
def __init__(self, ports, pool_port=50000):
"""Create a pool of servers. Uses a shared Queue to get available
servers.
Parameters
----------
ports : list(int)
List of ports at which the CodeServer's should run.
pool_port : int
Port at which the server pool should serve.
"""
self.my_port = pool_port
self.ports = ports
queue = Queue(maxsize=len(ports))
self.queue = queue
servers = []
for port in ports:
server = CodeServer(port, queue)
servers.append(server)
p = Process(target=server.run)
p.start()
self.servers = servers
def get_server_port(self):
"""Get available server port from ones in the pool. This will block
till it gets an available server.
"""
q = self.queue
was_waiting = True if q.empty() else False
port = q.get()
if was_waiting:
print '*'*80
print "No available servers, was waiting but got server \
later at %d." % port
print '*'*80
sys.stdout.flush()
return port
def run(self):
"""Run server which returns an available server port where code
can be executed.
"""
server = SimpleXMLRPCServer(("localhost", self.my_port))
self.server = server
server.register_instance(self)
server.serve_forever()
###############################################################################
def main():
run_as_nobody()
if len(sys.argv) == 1:
ports = SERVER_PORTS
else:
ports = [int(x) for x in sys.argv[1:]]
server_pool = ServerPool(ports=ports, pool_port=SERVER_POOL_PORT)
server_pool.run()
if __name__ == '__main__':
main()