Merge pull request #9650 from edx/gabe/fix-backend-order

Fix order of tracking backends

cms/envs/aws.py

@@ -293,8 +293,8 @@ BROKER_URL = "{0}://{1}:{2}@{3}/{4}".format(CELERY_BROKER_TRANSPORT,
 
 # Event tracking
 TRACKING_BACKENDS.update(AUTH_TOKENS.get("TRACKING_BACKENDS", {}))
-EVENT_TRACKING_BACKENDS['tracking_logs']['OPTIONS']['backends'].update(AUTH_TOKENS.get("EVENT_TRACKING_BACKENDS", {}))
-EVENT_TRACKING_BACKENDS['segmentio']['OPTIONS']['processors'][0]['OPTIONS']['whitelist'].extend(
+EVENT_TRACKING_BACKENDS['0_tracking_logs']['OPTIONS']['backends'].update(AUTH_TOKENS.get("EVENT_TRACKING_BACKENDS", {}))
+EVENT_TRACKING_BACKENDS['1_segmentio']['OPTIONS']['processors'][0]['OPTIONS']['whitelist'].extend(
     AUTH_TOKENS.get("EVENT_TRACKING_SEGMENTIO_EMIT_WHITELIST", []))
 
 SUBDOMAIN_BRANDING = ENV_TOKENS.get('SUBDOMAIN_BRANDING', {})

cms/envs/common.py

@@ -828,8 +828,12 @@ TRACKING_BACKENDS = {
 TRACKING_IGNORE_URL_PATTERNS = [r'^/event', r'^/login', r'^/heartbeat']
 
 EVENT_TRACKING_ENABLED = True
+
+# NOTE: the sort order of the backend names is important here, the events will be sent to the backends in sorted
+# order. In this case a processor modifies the event in a way that is only intended to be seen by segment.io, so
+# we want to make sure that backend and processor is run *after* the event has been sent to the tracking logs.
 EVENT_TRACKING_BACKENDS = {
-    'tracking_logs': {
+    '0_tracking_logs': {
         'ENGINE': 'eventtracking.backends.routing.RoutingBackend',
         'OPTIONS': {
             'backends': {
@@ -847,7 +851,7 @@ EVENT_TRACKING_BACKENDS = {
             ]
         }
     },
-    'segmentio': {
+    '1_segmentio': {
         'ENGINE': 'eventtracking.backends.routing.RoutingBackend',
         'OPTIONS': {
             'backends': {