SNI and advanced configuration of custom error pages

Configuration Samples
1

Is it possible to setup custom error pages in haproxy but only when the backend does not respond. ie when the backend is down haproxy sends out 503 error pages. We want our multidomain haproxy to send 503 error pages matching the domain requested.

We have tried setting up custom error pages like so:

http-errors domain1
    errorfile 503 /etc/haproxy/errors/503_domain1.http
http-errors domain2
    errorfile 503 /etc/haproxy/errors/503_domain.http

and in the frontend like so:

    http-response return status 503 errorfiles domain1 if { status 503 } { var(txn.host) www.domain1.com }
    http-response return status 503 errorfiles domain2 if { status 503 } { var(txn.host) domain2.com }

But that overrides all 503 error pages, also the ones sent from the backend and any custom headers set by the backend. We only want haproxy to send its own custom error pages if the backend does not respond. Is this possible?

2

I would declare errorfile(s) in each backend.

http-errors domain1
    errorfile 503 /etc/haproxy/errors/503_domain1.http
http-errors domain2
    errorfile 503 /etc/haproxy/errors/503_domain.http

backend domain1
    errorfiles domain1 503
    server server1 10.0.0.1:80

backend domain2
    errorfiles domain2 503
    server server2 10.0.0.2:80

# A way to declare an error file without having its own section.
backend domain3
    errorfile 503 /etc/haproxy/errors/503_domain3.http
    server server3 10.0.0.3:80