1 files changed, 78 insertions, 0 deletions
diff --git a/testapp/exam/xmlrpc_clients.py b/testapp/exam/xmlrpc_clients.py
new file mode 100644
index 0000000..817e37d
--- /dev/null
+++ b/testapp/exam/xmlrpc_clients.py
@@ -0,0 +1,78 @@
+from xmlrpclib import ServerProxy
+import time
+import random
+import socket
+
+from settings import SERVER_PORTS, SERVER_POOL_PORT
+
+
+class ConnectionError(Exception):
+    pass
+
+################################################################################
+# `CodeServerProxy` class.
+################################################################################
+class CodeServerProxy(object):
+    """A class that manages accesing the farm of Python servers and making
+    calls to them such that no one XMLRPC server is overloaded.
+    """
+    def __init__(self):
+        pool_url = 'http://localhost:%d'%(SERVER_POOL_PORT)
+        self.pool_server = ServerProxy(pool_url)
+        self.methods = {"python": 'run_python_code',
+                        "bash": 'run_bash_code'}
+    
+    def run_code(self, answer, test_code, user_dir, language):
+        """Tests given code (`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).  The parameter language specifies which language to use for the
+        tests.
+
+        Parameters
+        ----------
+        answer : str
+            The user's answer for the question.
+        test_code : str
+            The test code to check the user code with.
+        user_dir : str (directory)
+            The directory to run the tests inside.
+        language : str
+            The programming language to use.
+
+        Returns
+        -------
+        A tuple: (success, error message).
+        """
+        method_name = self.methods[language]
+        try:
+            server = self._get_server()
+            method = getattr(server, method_name)
+            result = method(answer, test_code, user_dir)
+        except ConnectionError:
+            result = [False, 'Unable to connect to any code servers!']
+        return result
+
+    def _get_server(self):
+        # Get a suitable server from our pool of servers.  This may block.  We
+        # try about 60 times, essentially waiting at most for about 30 seconds.
+        done, count = False, 60
+
+        while not done and count > 0:
+            try:
+                port = self.pool_server.get_server_port()
+            except socket.error:
+                # Wait a while try again.
+                time.sleep(random.random())
+                count -= 1
+            else:
+                done = True
+        if not done:
+            raise ConnectionError("Couldn't connect to a server!") 
+        proxy = ServerProxy('http://localhost:%d'%port)
+        return proxy
+
+# views.py calls this Python server which forwards the request to one
+# of the running servers.
+code_server = CodeServerProxy()
+