Verbose Backend Fetch Error - possible?

[Daniel Parthey]

Hi,

is there any way in varnish 4.1 to get the FetchError string from VSL (for example: first byte read failed) into a synthesized error message on backend fetch error, so that it does not only show "Backend fetch failed" to the user, but the detailed reason, because there are a lot of reasons why the backend fetch could have failed (connection refused, DNS lookup in named director failed, first byte timeout expired, etc.)

I would to generate a (maybe encrypted or obfuscated) verbose message, which the client user can provide to the sysadmin if the backend fails. The sysadmin will then be able to decrypt the message and immediately sees the detailed fetch error, without having to reproduce the issue or having to dig into varnish VSL.

Regards
Daniel