puppet: Declare upstreams properly in app nginx config.

(imported from commit 859eeed0d5b92c1b5b2b0764aba06aebcde8e2e2)

puppet/zulip/files/nginx/zulip-include-app.d/external-sso.conf

@@ -3,6 +3,6 @@
 # should pass REMOTE_USER to /accounts/login/sso/ once it has satisfactorily
 # identified the user.
 location /accounts/login/sso/ {
-    proxy_pass https://localhost:8888;
+    proxy_pass https://localhost_sso;
     include /etc/nginx/zulip-include/proxy;
 }

puppet/zulip/files/nginx/zulip-include-frontend/app

@@ -15,7 +15,7 @@ location /static/ {
 
 # Send longpoll requests to Tornado
 location ~ /json/get_events|/json/events|/api/v1/events {
-    proxy_pass       http://localhost:9993;
+    proxy_pass http://tornado;
     include /etc/nginx/zulip-include/proxy_longpolling;
 
     proxy_set_header X-Real-IP       $remote_addr;
@@ -23,14 +23,14 @@ location ~ /json/get_events|/json/events|/api/v1/events {
 
 # Send sockjs requests to Tornado
 location /sockjs {
-    proxy_pass http://localhost:9993;
+    proxy_pass http://tornado;
     include /etc/nginx/zulip-include/location-sockjs;
 }
 
 # Send everything else to Django via FastCGI
 location / {
     include fastcgi_params;
-    fastcgi_pass unix:/home/zulip/deployments/fastcgi-socket;
+    fastcgi_pass django;
     fastcgi_split_path_info ^()(.*)$;
     # Second number set to `getconf PAGESIZE`
     fastcgi_buffers 1024 4k;

puppet/zulip_internal/files/nginx/sites-available/zulip

@@ -14,6 +14,19 @@ server {
     return 301 https://$host$request_uri;
 }
 
+upstream django {
+    server_name unix:/home/zulip/deployments/fastcgi-socket;
+}
+
+upstream tornado {
+    server_name localhost:9993;
+    keepalive 10000;
+}
+
+upstream localhost_sso {
+    server_name localhost:8888;
+}
+
 server {
     listen 443;