527 Railgun Error

Deprecated Cloudflare code for a connection failure between the edge and a Railgun listener.

Status

HTTP/1.1 527 Railgun Error

Details

• Category: 5xx
• Status: Unofficial (Cloudflare). Not registered with IANA. A server, framework, or CDN convention.
• Specification: none, not defined by any RFC
• Cacheable: Not cacheable
• Response body: Allowed
• Retry: Retry after a delay

527 indicated that the connection between Cloudflare and a Railgun listener at the origin was interrupted. Railgun was a WAN optimization product that has since been retired, replaced by Argo Smart Routing.

You will only see it in historical logs from sites that ran Railgun.

Common causes

• The Railgun listener was down or unreachable from the edge.
• A network interruption between the edge and the listener.

How to fix it

As the client

• Retry. The condition is entirely on the edge to origin path.

As the server

• Migrate off Railgun, which is retired, to the current smart routing product.

Examples

HTTP/1.1 527
Server: cloudflare

See also

• HTTP response status codes
• 520 Web Server Returned an Unknown Error
• 522 Connection Timed Out
• 502 Bad Gateway