HAProxy uses a special configuration block, `resolvers`, to specify
how it should look up names in DNS. This configuration is used for
e.g. dynamically discovering backend servers via DNS A or SRV records.
Since resolvers are global, they need to be specified in the global
configuration file, rather than a per-application drop-in.
We will use this functionality for the ACME HTTP-01 challenge solver
for Samba AD domain controllers.
The current version of *haproxy* packaged in Fedora already enables
configuration via fragments in a drop-in directory, though it uses
a different path by default. I still like separating the global
configuration from the defaults, though, and keeping the main
`haproxy.cfg` file empty.
the `haproxy_ssl_default_bind_options` variable is not defined for
machines running Fedora, because this parameter is not used in the
default configuration file there.
Debian does not support system-wide SSL cipher suite profiles of course,
so these options need to be specified explicitly when deploying HAProxy
on Debian-based machines.
The *haproxy* installs HAproxy and sets up basic configuration for it.
It configures the systemd unit to launch the service with the `-f
/etc/haproxy` arguments, which will cause it to load all files from the
`/etc/haproxy` directory, instead of just `/etc/haproxy/haproxy.cfg`.
This will allow other roles to add frontend and backend configuration by
adding additional files to this directory.
Dustin