Merge pull request 'Allow to replace "app" server name in nginx by value of an env var' (#10) from mossroy/ttrss-docker-compose:replace-hardcoded-app-DNS-with-env-var into master

Reviewed-on: https://dev.tt-rss.org/tt-rss/ttrss-docker-compose/pulls/10

web-nginx/Dockerfile

@@ -2,4 +2,14 @@ FROM nginx:alpine
 
 HEALTHCHECK CMD curl --fail http://localhost/tt-rss/index.php || exit 1
 
-COPY nginx.conf /etc/nginx/nginx.conf
+COPY nginx.conf /etc/nginx/templates/nginx.conf.template
+
+# By default, nginx will send the php requests to "app" server, but this server
+# name can be overridden at runtime by passing an APP_UPSTREAM env var
+ENV APP_UPSTREAM=${APP_UPSTREAM:-app}
+
+# It's necessary to set the following NGINX_ENVSUBST_OUTPUT_DIR env var to tell
+# nginx to replace the env vars of /etc/nginx/templates/nginx.conf.template
+# and put the result in /etc/nginx/nginx.conf (instead of /etc/nginx/conf.d/nginx.conf)
+# See https://github.com/docker-library/docs/tree/master/nginx#using-environment-variables-in-nginx-configuration-new-in-119
+ENV NGINX_ENVSUBST_OUTPUT_DIR=/etc/nginx

web-nginx/nginx.conf

@@ -17,7 +17,7 @@ http {
 	index index.php;
 
 	upstream app {
-		server app:9000;
+		server ${APP_UPSTREAM}:9000;
 	}
 
 	server {