Merge pull request #56 from ankitjavalkar/examtime

Start and Expiry times for Quizzes

1 files changed, 162 insertions, 0 deletions

diff --git a/yaksh/code_server.py b/yaksh/code_server.py
new file mode 100755
index 0000000..2593752
--- /dev/null
+++ b/yaksh/code_server.py
@@ -0,0 +1,162 @@
+#!/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
+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
+import json
+# Local imports.
+from settings import SERVER_PORTS, SERVER_POOL_PORT
+from language_registry import set_registry, get_registry
+
+
+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)
+
+
+###############################################################################
+# `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
+
+    # Public Protocol ##########
+    def check_code(self, language, json_data, in_dir=None):
+        """Calls relevant EvaluateCode class based on language to check the
+         answer code
+        """
+        code_evaluator = self._create_evaluator_instance(language, json_data,
+                                                             in_dir)
+        result = code_evaluator.evaluate()
+
+        # Put us back into the server pool queue since we are free now.
+        self.queue.put(self.port)
+
+        return json.dumps(result)
+
+    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()
+
+    # Private Protocol ##########
+    def _create_evaluator_instance(self, language, json_data, in_dir):
+        """Create instance of relevant EvaluateCode class based on language"""
+        set_registry()
+        registry = get_registry()
+        cls = registry.get_class(language)
+        instance = cls.from_json(language, json_data, in_dir)
+        return instance
+
+
+###############################################################################
+# `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
+
+    # Public Protocol ##########
+
+    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(args=None):
+    run_as_nobody()
+    if args:
+        ports = [int(x) for x in args[1:]]
+    else:
+        ports = SERVER_PORTS
+
+    server_pool = ServerPool(ports=ports, pool_port=SERVER_POOL_PORT)
+    server_pool.run()
+
+if __name__ == '__main__':
+    args = sys.argv[1:]
+    main(args)