Use a tornado based server for the pool server.

With the previous XMLRPC based server, an XMLRPC server would respond to
a request for an available port.  This does not work as the server can
only take about 2 simultaneous connections.  The server pool now uses a
HTTP server via tornado which works extremely well.  The django code
should not change at all as this is an internal change.  This change
should make the code server far more robust and work for a very large
number of simultaneous users.

The http server also has a simple status page to indicate the current
load.  This will not be correct on OSX due to limitations of the
multi-processing Queue implementation on OSX.

1 files changed, 4 insertions, 17 deletions

diff --git a/yaksh/xmlrpc_clients.py b/yaksh/xmlrpc_clients.py
index 7124550..6bfe0d6 100644
--- a/yaksh/xmlrpc_clients.py
+++ b/yaksh/xmlrpc_clients.py
@@ -3,6 +3,7 @@ import time
 import random
 import socket
 import json
+import urllib
 
 from settings import SERVER_PORTS, SERVER_POOL_PORT
 
@@ -21,7 +22,7 @@ class CodeServerProxy(object):
     """
     def __init__(self):
         pool_url = 'http://localhost:%d' % (SERVER_POOL_PORT)
-        self.pool_server = ServerProxy(pool_url)
+        self.pool_url = pool_url
 
     def run_code(self, language, test_case_type, json_data, user_dir):
         """Tests given code (`answer`) with the `test_code` supplied.  If the
@@ -34,7 +35,7 @@ class CodeServerProxy(object):
         ----------
         json_data contains;
         user_answer : str
-            The user's answer for the question. 
+            The user's answer for the question.
         test_code : str
             The test code to check the user code with.
         language : str
@@ -57,21 +58,7 @@ class CodeServerProxy(object):
         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!")
+        port = json.loads(urllib.urlopen(self.pool_url).read())
         proxy = ServerProxy('http://localhost:%d' % port)
         return proxy