Varnish5 PROXY protocol and health probes

[Florian Tham]

Hi,

I'm using varnish-5.0.0 with PROXY protocol enabled on the backends
thanks to the new .proxy_header attribute. This works great as long as
the backends don't have health probes defined. When a backend has both
a .proxy_header attribute and a probe defined, varnish fails to
properly detect the backend health state and marks the backend as
sick.

The problem seems to be that varnish does not use the PROXY protocol
when sending health probes. If the backend correctly implements the
PROXY protocol, it is required to drop the connection, as it cannot
identify it as valid PROXY protocol v1 nor v2. Thus, from varnish's
pov the backend is unreachable.

I think it would be pretty useful to have health probes handle the
PROXY protocol as well. What do you think? Are there any plans to
enhance varnish accordingly?

Best regards,

Florian