Error pages of the proxy

If the proxy cannot send a request to your app, it answers with its own page and an x-ferry-error header.

Terminal

$ curl -sI http://nope.localhost:8080/HTTP/1.1 404 Not Foundx-ferry-error: not_found

If the proxy cannot send a request to your app, it answers with its own HTML page. The answer has an x-ferry-error header.

Thus you can tell an error of the proxy from an error of your app.

The errors

Status	`x-ferry-error`	Cause
`400`	`bad_request`	The request has no `Host` header, has two, or has a bad one.
`404`	`not_found`	No service owns this host. The page says "No service is configured for …".
`405`	`method_not_allowed`	The request is a `CONNECT` request.
`408`	`request_timeout`	The client sent no part of its request body for 60 seconds.
`503`	`suspended`	You suspended the service.
`503`	`no_upstreams`	The service has no instance that runs. See below.
`502`	`bad_gateway`	The instance refused the connection, or failed in the middle of the request.

The answer has the header Retry-After: 5.