title: Does nginx fastcgi_pass support variables?
body: <p>I would like to use <a href="https://serverfault.com/questions/240476/how-to-force-nginx-to-resolve-dns-of-a-dynamic-hostname-everytime-when-doing-p">dynamic host resolution</a> with nginx and fastcgi_pass.</p>
  
  <p>When <code>fastcgi_pass $wphost:9000;</code> is set in the conf then nginx displays the error 
  <code>[error] 7#7: *1 wordpress.docker could not be resolved (3: Host not found),</code></p>
  
  <p>but when I set  <code>fastcgi_pass wordpress.docker:9000;</code>it is working except for the fact the that after a wordpress restart nginx still points to an old ip.</p>
  
  <pre><code>server {
    listen [::]:80;
    include /etc/nginx/ssl/ssl.conf;
  
    server_name app.domain.*;
  
    root /var/www/html;
    index index.php index.html index.htm;
  
    resolver 172.17.42.1 valid=60s; 
    resolver_timeout 3s;
  
    location / {
      try_files $uri $uri/ /index.php?q=$uri&amp;$args; ## First attempt to serve request as file, then as directory, then fall back to index.html
    }
  
    #error_page 404 /404.html;
    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
      root /usr/share/nginx/html;
    }
  
    set $wphost wordpress.docker;  
  
    # pass the PHP scripts to FastCGI server listening on wordpress.docker
    location ~ \.php$ {
      client_max_body_size    25M;
      try_files               $uri =404;
      fastcgi_split_path_info ^(.+\.php)(/.+)$;
      fastcgi_pass            $wphost:9000;
      fastcgi_param           SCRIPT_FILENAME $document_root$fastcgi_script_name;
      fastcgi_param           SCRIPT_NAME $fastcgi_script_name;
      fastcgi_index           index.php;
      include                 fastcgi_params;
    }
  
    location ~* \.(jpg|jpeg|gif|png|css|js|ico|xml)$ {
      add_header        Pragma public;
      add_header        Cache-Control "public, must-revalidate, proxy-revalidate";
      access_log        off;
      log_not_found     off;
      expires           168h;
    }
  
    # deny access to . files, for security
    location ~ /\. {
          access_log    off;
          log_not_found off; 
          deny          all;
    }
  
  }
  </code></pre>
  
  <p>I have different virtual host configuration where I use <code>proxy_pass http://$hostname;</code> and in this setup everything is working as expected and the host is found.</p>
  
  <p>After trying different options I wonder if <code>fastcgi_pass</code> does support variables</p>