https://stackonward.com/tags/docker-networking/Recent content in Docker Networking on StackOnwardHugoen-USFri, 11 Sep 2026 05:08:00 +0800https://stackonward.com/posts/502-504-troubleshooting/Fri, 11 Sep 2026 05:08:00 +0800https://stackonward.com/posts/502-504-troubleshooting/<p>How to troubleshoot 502 and 504 starts at the hop that produced the status. Both codes come from a gateway or reverse proxy: 502 Bad Gateway means that hop did not get a usable response from upstream; 504 Gateway Timeout means it waited past its limit. Keep the headers, then reach the upstream from that hop&rsquo;s network.</p> <figure> <img src="https://stackonward.com/images/posts/502-504-troubleshooting/en/gateway-failure-map.svg" alt="A client reaches an app through a CDN and reverse proxy; a failed connection becomes 502, a wait past the limit becomes 504" loading="lazy" decoding="async"> <figcaption>Connection refused, DNS failure, and an invalid response usually point to 502. An upstream wait past the proxy deadline usually points to 504.</figcaption> </figure> <h2 id="how-to-troubleshoot-502-and-504-at-the-hop-that-returned-the-status">How to troubleshoot 502 and 504 at the hop that returned the status</h2> <p>A browser may sit behind Cloudflare or another CDN, a cloud load balancer, and Caddy or Nginx. Save the status, headers, time, and request ID:</p>