msergo · September 1, 2018 16:21 · Oct 10, 2014 · May 13, 2014
diff --git a/nginx-environment.md b/nginx-environment.md
@@ -26,7 +26,7 @@ The solution
 So this is what I did: I created the base configuration file, named it `proxy.conf` and setup docker to add it to the `conf.d` directory while building the image. The command is:
 
 ```
-ADD proxy.cond /etc/nginx/conf.d/proxy.conf
+ADD proxy.conf /etc/nginx/conf.d/proxy.conf
 ```
 
 In the `proxy.conf`, I omitted the `upstream` configuration, leaving that for later. I created another file, a `run.sh` file and added it to the image using the Dockerfile. The file was as follows:

diff --git a/nginx-environment.md b/nginx-environment.md
@@ -0,0 +1,50 @@
+How to add environment variables to nginx.conf
+===============================================
+
+This is the hack approach to adding environment variables to the nginx configuration files. As with most Google results for this search, the reason is Docker.
+
+The setup
+---------
+
+I intended to deploy two [Docker](http://docker.io) containers. 
+
+1. An instance of an HTTP server providing a REST service (in my case, a JBoss application server running a Spring application)
+2. An nginx that provides a proxy to the REST service.
+
+Why would I want to use a proxy? Load balancing, caching, firewalling... in my case, it was that the original application did not provide [CORS](http://enable-cors.org/) and the nginx configuration does. You can see the nginx configuration in the proxy.conf file.
+
+The problem
+-----------
+
+Both the port and the IP address of the JBoss instance are assigned by Docker dynamically. [Docker provides a linking feature](http://docs.docker.io/use/working_with_links_names/#links-service-discovery-for-docker) for service discovery that allows Docker containers to know the IP and port of services running on a specific container, but the quirk is that it relies on environment variables.
+
+I'm not actually certain that adding environment variables to an nginx configuration file is impossible, but its at the very least very hard. 
+
+The solution
+------------
+
+So this is what I did: I created the base configuration file, named it `proxy.conf` and setup docker to add it to the `conf.d` directory while building the image. The command is:
+
+```
+ADD proxy.cond /etc/nginx/conf.d/proxy.conf
+```
+
+In the `proxy.conf`, I omitted the `upstream` configuration, leaving that for later. I created another file, a `run.sh` file and added it to the image using the Dockerfile. The file was as follows:
+
+```bash
+#!/bin/sh
+
+(echo "upstream theservice { server $JBOSS_PORT_8080_TCP_ADDR:$JBOSS_PORT_8080_TCP_PORT; }" && cat /etc/nginx/conf.d/proxy.conf) > proxy.conf.new
+mv proxy.conf.new /etc/nginx/conf.d/proxy.conf
+service nginx start
+```
+
+What does is, it prepends the line with the upstream configuration.
+
+Finally, I run the nginx from the `run.sh` script. The Dockerfile command:
+
+```
+CMD bash run.sh
+```
+
+The trick is that since the container is initialized like that, the configuration file does not get permanently written and the configuration is updated accordingly.
diff --git a/proxy.conf b/proxy.conf
@@ -0,0 +1,32 @@
+# This part is omitted
+# upstream theservice {
+#    server 127.0.0.1:8082;
+# }
+
+server {
+  listen 80;
+
+  location / {
+
+    access_log off;
+    proxy_pass http://theservice;
+
+    add_header Access-Control-Allow-Origin *;
+    add_header Access-Control-Allow-Credentials true;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header Host $host;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+
+    if ($request_method = OPTIONS ) {
+      add_header Access-Control-Allow-Origin "*";
+      add_header Access-Control-Allow-Methods "GET,POST,OPTIONS,PUT,DELETE,PATCH";
+      add_header Access-Control-Allow-Headers 'Authorization,Content-Type,Accept,Origin,User-Agent,DNT,Cache-Control,X-Mx-ReqToken,Keep-Alive,X-Requested-With,If-Modified-Since';
+      add_header Access-Control-Allow-Credentials "true";
+      add_header 'Access-Control-Max-Age' 1728000;
+      add_header Content-Length 0;
+      add_header Content-Type text/plain;
+      add_header Cache-Control 'max-age=0';
+      return 204;
+    }
+  }
+}
diff --git a/run.sh b/run.sh
@@ -0,0 +1,11 @@
+#!/bin/sh
+
+# Preprend the upstream configuration
+(echo "upstream theservice { server $JBOSS_PORT_8080_TCP_ADDR:$JBOSS_PORT_8080_TCP_PORT; }" && cat /etc/nginx/conf.d/proxy.conf) > proxy.conf.new
+mv proxy.conf.new /etc/nginx/conf.d/proxy.conf
+
+# Log the resulting configuration file
+cat /etc/nginx/conf.d/proxy.conf
+
+# Start nginx
+service nginx start
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