GCal: Better Callback management

- when callback of an old channel is received this channel is canceled automatically

eventplanner_gcal/google_sync.py

@@ -332,3 +332,36 @@ def stopAllGCalSubscriptions( service=None ):
     for dbChannel in GCalPushChannel.objects.all():
         print("Stopping %s expiry at %d " % ( dbChannel.id, dbChannel.expiration ) )
         GCalPushChannel.stop( service, dbChannel.toGChannel() )
+
+
+def checkIfGoogleCallbackIsValid( token, channelID, resourceID, service=None ):
+    if service is None: service = getServiceObject()
+
+    allChannels = GCalPushChannel.objects.all()
+    if len(allChannels) == 0:
+        return False # no known subscriptions -> callback has to be from an old channel
+
+    if len(allChannels) > 1:
+        logger.warning( "Multiple GCal subscriptions! This is strange and probably an error. "
+                        "All channels are closed and one new is created. ")
+        stopAllGCalSubscriptions( service )
+        checkGCalSubscription()
+        allChannels = GCalPushChannel.objects.all()
+
+    assert( len(allChannels) == 1 )
+
+    theChannel = allChannels[0]
+
+    if channelID != theChannel.id or resourceID != theChannel.resource_id or token != theChannel.token:
+        logger.warning( "Got GCal Response from an unexpected Channel"
+                        "Got      (%s,%s,%s) "
+                        "expected (%s,%s,%s) "
+                        "Old Channel is stopped."
+                        % ( channelID, resourceID,token, theChannel.id, theChannel.resource_id, theChannel.token ))
+
+        channelToStop = GCalPushChannel( id = channelID, resource_id = resourceID, token = token )
+        GCalPushChannel.stop( service, channelToStop.toGChannel() )
+
+        return False
+
+    return True

eventplanner_gcal/views.py

@@ -3,6 +3,7 @@ from eventplanner_gcal.google_sync import syncFromGoogleToLocal, syncFromLocalTo
 from django.http import HttpResponse
 from django.views.decorators.csrf import csrf_exempt
 from pprint import pformat
+from eventplanner_gcal.google_sync import checkIfGoogleCallbackIsValid
 
 import logging
 
@@ -16,15 +17,23 @@ def runSync( request ):
 @csrf_exempt
 def gcalApiCallback( request ):
     # TODO check channel info here
-    requestMetaStr = pformat( request.META )
+    token = ""
-    logger.info( "Received Google Callback with the following headers:\n" + requestMetaStr )
+    if 'HTTP_X_GOOG_CHANNEL_TOKEN' in request.META: token = request.META['HTTP_X_GOOG_CHANNEL_TOKEN']
+    channelID = ""
+    if 'HTTP_X_GOOG_CHANNEL_ID' in request.META: channelID = request.META['HTTP_X_GOOG_CHANNEL_ID']
+    resourceID = ""
+    if 'HTTP_X_GOOG_RESOURCE_ID' in request.META: resourceID = request.META['HTTP_X_GOOG_RESOURCE_ID']
+
+    valid = checkIfGoogleCallbackIsValid( token, channelID, resourceID)
+
+    if not valid:
+        return HttpResponse('<h1>Old Channel - no update triggered</h1>')
+
+
+    logger.info( "Received Google Callback with the following headers Token: %s ID %s ResID %s " % ( token, channelID, resourceID ) )
     result = syncFromGoogleToLocal()
-    logger.info("Finished processing callback from GCal - New Information present: %1 " %(result, ) )
+    logger.info("Finished processing callback from GCal - New Information present: %d " %(result, ) )
     return HttpResponse('<h1>Callback successful</h1>')
 
 
 
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