Allow nginx not to depend on lms/cms

By using variables in the nginx configuration to point to lms/cms, we
allow nginx not to require that lms and cms are up to run. This is
convenient for debugging production settings: just launch an nginx, then
runserver in an lms.

docker-compose.yml

@@ -38,8 +38,6 @@ services:
     volumes:
       - ./data/lms:/openedx/data/lms:ro
       - ./data/cms:/openedx/data/cms:ro
-    depends_on:
-      - lms
 
   rabbitmq:
     image: rabbitmq:3.6.10
@@ -77,7 +75,11 @@ services:
     volumes:
       - ./data/cms:/openedx/data
     depends_on:
-      - lms
+      - memcached
+      - mongodb
+      - mysql
+      - rabbitmq
+      - smtp
 
   ############# LMS and CMS workers
 

nginx/config/templates/cms.conf.templ

@@ -1,7 +1,3 @@
-upstream cms-backend {
-  server cms:8000 fail_timeout=0;
-}
-
 server {
   listen 80;
   server_name £{CMS_HOST};
@@ -23,11 +19,13 @@ server {
     proxy_set_header X-Forwarded-Proto $scheme;
     proxy_set_header X-Forwarded-Port $server_port;
     proxy_set_header X-Forwarded-For $remote_addr;
-    
     proxy_set_header Host $http_host;
-
     proxy_redirect off;
-    proxy_pass http://cms-backend;
+
+    # Docker resolver
+    resolver 127.0.0.11 valid=10s;
+    set $upstream cms;
+    proxy_pass http://$upstream:8000;
   }
 
   location / {

nginx/config/templates/lms.conf.templ

@@ -1,7 +1,3 @@
-upstream lms-backend {
-  server lms:8000 fail_timeout=0;
-}
-
 server {
   listen 80;
   server_name £{LMS_HOST};
@@ -23,11 +19,13 @@ server {
     proxy_set_header X-Forwarded-Proto $scheme;
     proxy_set_header X-Forwarded-Port $server_port;
     proxy_set_header X-Forwarded-For $remote_addr;
-    
     proxy_set_header Host $http_host;
-
     proxy_redirect off;
-    proxy_pass http://lms-backend;
+
+    # Docker resolver
+    resolver 127.0.0.11 valid=10s;
+    set $upstream lms;
+    proxy_pass http://$upstream:8000;
   }
 
   location / {