Move xqueue_interface to lib/capa

common/lib/capa/capa/responsetypes.py

@@ -22,10 +22,10 @@ import abc
 # specific library imports
 from calc import evaluator, UndefinedVariable
 from correctmap import CorrectMap
-from courseware import xqueue_interface
 from util import *
 from lxml import etree
 from lxml.html.soupparser import fromstring as fromstring_bs	 # uses Beautiful Soup!!! FIXME?
+import xqueue_interface
 
 log = logging.getLogger('mitx.' + __name__)
 

common/lib/capa/capa/xqueue_interface.py

@@ -0,0 +1,87 @@
+#
+#  LMS Interface to external queueing system (xqueue)
+#
+import hashlib
+import json
+import requests
+import time
+
+# TODO: Collection of parameters to be hooked into rest of edX system
+XQUEUE_LMS_AUTH = { 'username': 'LMS',
+                    'password': 'PaloAltoCA' }
+XQUEUE_SUBMIT_URL = 'http://xqueue.edx.org'
+
+def make_hashkey(seed=None):
+    '''
+    Generate a string key by hashing 
+    '''
+    h = hashlib.md5()
+    if seed is not None:
+        h.update(str(seed))
+    h.update(str(time.time()))
+    return h.hexdigest()
+
+
+def make_xheader(lms_callback_url, lms_key, queue_name):
+    '''
+    Generate header for delivery and reply of queue request.
+
+    Xqueue header is a JSON-serialized dict:
+        { 'lms_callback_url': url to which xqueue will return the request (string),
+          'lms_key': secret key used by LMS to protect its state (string), 
+          'queue_name': designate a specific queue within xqueue server, e.g. 'MITx-6.00x' (string)
+        }
+    '''
+    return json.dumps({ 'lms_callback_url': lms_callback_url,
+                        'lms_key': lms_key,
+                        'queue_name': queue_name })
+
+
+def send_to_queue(header, body, xqueue_url=None):
+    '''
+    Submit a request to xqueue.
+    
+    header: JSON-serialized dict in the format described in 'xqueue_interface.make_xheader'
+
+    body: Serialized data for the receipient behind the queueing service. The operation of
+            xqueue is agnostic to the contents of 'body'
+
+    Returns an 'error' flag indicating error in xqueue transaction
+    '''
+    if xqueue_url is None:
+        xqueue_url = XQUEUE_SUBMIT_URL
+
+    # First, we login with our credentials
+    #------------------------------------------------------------
+    s = requests.session()
+    try:
+        r = s.post(xqueue_url+'/xqueue/login/', data={ 'username': XQUEUE_LMS_AUTH['username'],
+                                                       'password': XQUEUE_LMS_AUTH['password'] })
+    except Exception as err:
+        msg = 'Error in xqueue_interface.send_to_queue %s: Cannot connect to server url=%s' % (err, xqueue_url)
+        raise Exception(msg)
+
+    # Xqueue responses are JSON-serialized dicts
+    xreply = json.loads(r.text)
+    return_code = xreply['return_code']
+    if return_code: # Nonzero return code from xqueue indicates error
+        print '  Error in queue_interface.send_to_queue: %s' % xreply['content']
+        return 1 # Error
+
+    # Next, we can make a queueing request
+    #------------------------------------------------------------
+    payload = {'xqueue_header': header,
+               'xqueue_body'  : body}
+    try:
+        # Send request
+        r = s.post(xqueue_url+'/xqueue/submit/', data=payload)
+    except Exception as err:
+        msg = 'Error in xqueue_interface.send_to_queue %s: Cannot connect to server url=%s' % (err, xqueue_url)
+        raise Exception(msg)
+
+    xreply = json.loads(r.text)
+    return_code = xreply['return_code']
+    if return_code:
+        print '  Error in queue_interface.send_to_queue: %s' % xreply['content']
+
+    return return_code