2016-03-19 19:56:58 +00:00
|
|
|
# Writing middleware
|
|
|
|
|
|
|
|
|
|
From the Caddy docs:
|
|
|
|
|
|
|
|
|
|
> Oh yes, those pesky return values on ServeHTTP(). You read the documentation so you already know
|
|
|
|
|
> what they mean. But what does that imply for the behavior of your middleware?
|
|
|
|
|
>
|
|
|
|
|
> Basically, return a status code only if you did NOT write to the response body. If you DO write to
|
|
|
|
|
> the response body, return a status code of 0. Return an error value if your middleware encountered
|
|
|
|
|
> an error that you want logged. It is common to return an error status and an error value together,
|
|
|
|
|
> so that the error handler up the chain can write the correct error page.
|
|
|
|
|
>
|
|
|
|
|
> The returned status code is not logged directly; rather, it tells middleware higher up the chain
|
|
|
|
|
> what status code to use if/when the response body is written. Again, return a 0 status if you've
|
|
|
|
|
> already written a body!
|
|
|
|
|
|
|
|
|
|
In the DNS status codes are called rcodes and it's slightly harder to return the correct
|
|
|
|
|
answer in case of failure.
|
|
|
|
|
|
2016-03-19 20:53:37 +00:00
|
|
|
So CoreDNS treats
|
|
|
|
|
|
|
|
|
|
* SERVFAIL (dns.RcodeServerFailure)
|
|
|
|
|
* REFUSED (dns.RecodeRefused)
|
|
|
|
|
* FORMERR (dns.RcodeFormatError)
|
|
|
|
|
* NOTIMP (dns.RcodeNotImplemented)
|
|
|
|
|
|
|
|
|
|
as special and will then assume nothing has written to the client. In all other cases it is assume
|
|
|
|
|
something has been written to the client.
|
