Varnish backend request sent to itself?

[Martynas Jusevičius]

Nevermind, I figured out I wasn't even passing my VCL config correctly :)

On Wed, Mar 18, 2020 at 11:41 AM Martynas Jusevičius
<martynas at atomgraph.com> wrote:
>
> My attempt to obfuscate the hosts failed :) Sorry for that.
>
> In short: the configured backend is atomgraph.dydra.com but
> BereqHeader Host is atomgraph.dydra.varnish. Why?
>
> On Wed, Mar 18, 2020 at 11:36 AM Martynas Jusevičius
> <martynas at atomgraph.com> wrote:
> >
> > Hi,
> >
> > I'm using varnish-5.2.1 revision 67e562482 as a Docker image and
> > trying to restore the setup that was working some time ago.
> >
> > However I'm getting 503 Backend fetch failed.
> >
> > The VCL file clearly specifies the backend:
> >
> > backend default {
> >     .host = "atomgraph.some_host.com";
> >     .port = "80";
> >     .first_byte_timeout = 60s;
> > }
> >
> > Varnish itself runs on atomgraph.some_host.varnish, as specified in
> > docker-compose.yml.
> >
> > When I login into the container, I see the client request:
> >
> > -   ReqMethod      GET
> > -   ReqURL         /smth/smth/...
> > -   ReqProtocol    HTTP/1.1
> > -   ReqHeader      Accept:
> > application/rdf+xml,text/rdf+n3,application/n-triples,text/csv,application/rdf+xml,application/rdf+thrift,text/turtle,application/rdf+json
> > -   ReqHeader      Cache-Control: no-cache
> > -   ReqHeader      Authorization: Basic bGlua2VkZGF0YWh1YjpqYThhc3BhdHV0YWtFdGhV
> > -   ReqHeader      Host: atomgraph.dydra.varnish
> > -   ReqHeader      Connection: Keep-Alive
> > -   ReqHeader      User-Agent: Apache-HttpClient/4.1.1 (java 1.5)
> > -   ReqHeader      X-Forwarded-For: 172.30.0.3
> >
> > However when I look at the backend request:
> >
> > -   BereqMethod    GET
> > -   BereqURL       /smth/smth/...
> > -   BereqProtocol  HTTP/1.1
> > -   BereqHeader    Accept:
> > application/rdf+xml,text/rdf+n3,application/n-triples,text/csv,application/rdf+xml,application/rdf+thrift,text/turtle,application/rdf+json
> > -   BereqHeader    Authorization: Basic bGlua2VkZGF0YWh1YjpqYThhc3BhdHV0YWtFdGhV
> > -   BereqHeader    Host: atomgraph.dydra.varnish
> > -   BereqHeader    User-Agent: Apache-HttpClient/4.1.1 (java 1.5)
> > -   BereqHeader    X-Forwarded-For: 172.30.0.3
> > -   BereqHeader    X-Varnish: 32783
> >
> > it looks like it is calling itself (i.e. the local fake .varnish
> > backend host instead of the real .com one), judging from the
> > BereqHeader Host.
> >
> > If that is the case, then no wonder that the backend request fails:
> >
> > -   BerespProtocol HTTP/1.1
> > -   BerespStatus   503
> > -   BerespReason   Service Unavailable
> > -   BerespReason   Backend fetch failed
> >
> > How can this be?
> >
> > Martynas