title: Where do values come from in nginx.conf.erb file?
body: <p>I'm using Phusion Passenger with Rails (standalone) running on Heroku. The config file is passed in the Procfile settings.</p>
  
  <p>I'd like to change the historical nginx.conf.erb file. I can easily add new values, but it isn't obvious to me where the variable values are coming from.</p>
  
  <p>Examples from the file:</p>
  
  <pre><code>error_log '&lt;%= @options[:log_file] %&gt;' &lt;% if @options[:log_level] &gt;= LVL_DEBUG %&gt;info&lt;% end %&gt;;
  pid '&lt;%= @options[:pid_file] %&gt;';
  </code></pre>
  
  <p>or </p>
  
  <pre><code>&lt;%= nginx_option :passenger_log_level, :log_level %&gt;
  </code></pre>
  
  <p>or</p>
  
  <pre><code>&lt;% for app in @apps %&gt;
  server {
      &lt;% if app[:ssl] %&gt;
          &lt;% if app[:ssl_port] %&gt;
              listen &lt;%= nginx_listen_address(app) %&gt;;
              listen &lt;%= nginx_listen_address_with_ssl_port(app) %&gt; ssl;
          &lt;% else %&gt;
              listen &lt;%= nginx_listen_address(app) %&gt; ssl;
          &lt;% end %&gt;
      &lt;% else %&gt;
          listen &lt;%= nginx_listen_address(app) %&gt;;
      &lt;% end %&gt;
      server_name &lt;%= app[:server_names].join(' ') %&gt;;
  </code></pre>
  
  <p>So where are @options, @app coming from?</p>