I've recently taken over an environment using HAProxy, and I'm attempting to learn the config and what it all means, but I'm finding some aspects of it are not clear.
I think the above means that if host header begins with "foo.bar.com" then use the cdn cdn_name, but I'm not totally sure. Can somebody confirm for me?
Thanks!
Close.
It's defining an ACL with the name cdn_name, with the criteria hdr_beg(host) -i foo.bar.com. The criteria basically means that the HTTP Host: header begins with "foo.bar.com" and it uses case-insensitive matching (the "-i" flag).
On it's own this doesn't actually do anything, but it will be used further down your config, where you will likely see something like this:
<something something> if cdn_name
What this does is if the client request uses a Host: header that begins with "foo.bar.com", HAproxy will do whatever is defined in the <something something> bit of the config.
