amazon elastic beanstalk - How to configure .ebextensions for nginx location directive?

Question

I want to configure my staging environment in Elastic Beanstalk to always disallow all spiders. The nginx directive would look like this:

location /robots.txt {
    return 200 "User-agent: *
Disallow: /";
}

I understand that I would want to create a file under the .ebextensions/ folder, such as 01_nginx.config, but I'm not sure how to structure the YAML inside it such that it would work. My goal is to add this location directive to existing configuration, not have to fully replace any existing configuration files which are in place.

Answer 1

I wanted to do the same thing. After a lot of digging, I found 2 ways to do it:

Option 1. Use an ebextension to replace the nginx configuration file with your custom configuration

I used this option because it is the simplest one.

Following the example given by Amazon in Using the AWS Elastic Beanstalk Node.js Platform - Configuring the Proxy Server - Example .ebextensions/proxy.config, we can see that they create an ebextension that creates a file named /etc/nginx/conf.d/proxy.conf. This file contains the same content as the original nginx configuration file. Then, they delete the original nginx configuration file using container_commands.

You need to replace the Amazon example with the contents of your current nginx configuration file. Note that the nginx configuration files to be deleted in the containter command must be updated too. The ones I used are:

• nginx configuration file 1: /opt/elasticbeanstalk/support/conf/webapp_healthd.conf
• nginx configuration file 2: /etc/nginx/conf.d/webapp_healthd.conf

Therefore, the final ebextension that worked for me is as follows:

/.ebextensions/nginx_custom.config

# Remove the default nginx configuration generated by elastic beanstalk and
# add a custom configuration to include the custom location in the server block.
# Note that the entire nginx configuration was taken from the generated /etc/nginx/conf.d/webapp_healthd.conf file
# and then, we just added the extra location we needed.

files:
  /etc/nginx/conf.d/proxy_custom.conf:
    mode: "000644"
    owner: root
    group: root
    content: |
      upstream my_app {
        server unix:///var/run/puma/my_app.sock;
      }

      log_format healthd '$msec"$uri"'
                      '$status"$request_time"$upstream_response_time"'
                      '$http_x_forwarded_for';

      server {
        listen 80;
        server_name _ localhost; # need to listen to localhost for worker tier

        if ($time_iso8601 ~ "^(d{4})-(d{2})-(d{2})T(d{2})") {
          set $year $1;
          set $month $2;
          set $day $3;
          set $hour $4;
        }

        access_log  /var/log/nginx/access.log  main;
        access_log /var/log/nginx/healthd/application.log.$year-$month-$day-$hour healthd;

        location / {
          proxy_pass http://my_app; # match the name of upstream directive which is defined above
          proxy_set_header Host $host;
          proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }

        location /assets {
          alias /var/app/current/public/assets;
          gzip_static on;
          gzip on;
          expires max;
          add_header Cache-Control public;
        }

        location /public {
          alias /var/app/current/public;
          gzip_static on;
          gzip on;
          expires max;
          add_header Cache-Control public;
        }

        location /robots.txt {
          return 200 "User-agent: *
Disallow: /";
        }
      }

container_commands:
  # Remove the default nginx configuration generated by elastic beanstalk
 removeconfig:
    command: "rm -f /opt/elasticbeanstalk/support/conf/webapp_healthd.conf /etc/nginx/conf.d/webapp_healthd.conf"

Once you deploy this change, you have to reload the nginx server. You can connect to your server using eb ssh your-environment-name and then run sudo service nginx reload

Option 2. Use an ebextension to modify the nginx configuration file generator, so that it includes your custom locations in the final nginx configuration file

The second option is based on this post: jabbermarky's answer in Amazon forums

He explains this method very well in his answer, so I encourage you to read it if you want to implement it. If you are going to implement this answer, you need to update the location of the nginx file configuration generator.

Note that I have not tested this option.

In summary, he adds a shell script to be executed before the nginx configuration file is generated. In this shell script, he modifies the nginx configuration file generator to include the server block locations he wants in the generated nginx configuration file. Finally, he adds a file containing the locations he wants in the server block of the final nginx configuration file.