Cannot open website: 504 Gateway Timeout

Symptoms

• Cannot open website: it loads a long time and fails with 504 error;

• /var/www/vhosts/system/example.com/logs/proxy_error_log contains the following entries:

  CONFIG_TEXT: [error] upstream timed out (110: Connection timed out) while reading response header from upstream, client: 203.0.113.4, server: example.com, request: "GET / HTTP/1.1", upstream: "https://203.0.113.2:7081/", host: "www.example.com"
  [error] upstream prematurely closed connection while reading response header from upstream, client: 203.0.113.4, server: example.com, request: "GET / HTTP/1.1", upstream: "https://203.0.113.2:7081/", host: "www.example.com", referrer: "http://www.example.com"

• Website is based on WordPress;

• Subscription > example.com > Apache & nginx Settings > Additional nginx directives contain a custom rule for permalinks;

• Quite a few website pages show 404 error.

Cause

Incorrect nginx directives for permalinks.

Resolution

Use directives provided in KB article: A WordPress website shows 404 Not Found on all pages except index.php.