Feature request for remapping rules via SRV records

[tuaris]

I wrote a very crude C program (with some help getting started using AI) for fetching SRV records to generate a remap.confg file. I called it trafficmap. It takes in a text file with a list of domains. One would run the program and then reload traffic server.

SRV records look like this:

_http._tcp		IN	SRV	5 0 8002 web03.domain.tld.
_http._tcp.www	IN	SRV	5 0 8002 web03.domain.tld.

The resulting remap.config looks like this:

map http://mywebsite.tld http://web03.domain.tld:8002
map http://www.mywebsite.tld  http://web03.domain.tld:8002

I'd like to see a feature in Traffic Server where this would happen in real time with caching (while respecting TTL). Without having the need to pre-generate any configuration. Changes and new additions would propagate automatically through DNS. A plugin would be fine, but I'd prefer to not have that via Lua scripting/plugin.

[mlibbey]

If I'm understanding correctly you can set proxy.config.srv_enabled to 1 to use SRV for the origin -- so if you had
map http://mywebsite.tld https://origindomain.tld
with the setting (either in records.yaml or via the conf_remap plugin)
and
dig _https._tcp.origindomain.tld -t SRV
_https._tcp.origindomain.tld IN SRV 5 0 8002 web03.domain.tld.
_https._tcp.origindomain.tld IN SRV 5 0 8002 web04.domain.tld.
_https._tcp.origindomain.tld IN SRV 5 0 8002 web05.domain.tld.

you'd round robin across the 3 web0[#]

[tuaris]

It does indeed work. Is this a relatively new feature? I'm almost certain I spent time lots of researching this more than a year ago.

This part of the docs confuse me:

Also note that the port returned in the SRV record MUST match the port being used for the origin (e.g. if the origin scheme is http and a default port, there should be a SRV record with port 80).

I assume that's referring to the protocol (_http._tcp) and not the SRV location port number.

If the SRV records exists in the same zone I would end up building a remap.config file that looks like this:

map http://domain.tld http://domain.tld
map http://www.domain.tld http://www.domain.tld

It's satisfying, but the syntax can probably be improved.

Maybe do away with having to build mappings and provide Traffic Server a list of domains.

[mlibbey]

I'd love to improve the docs! What about adding more to the example. Like,

For instance, if the origin is set to https://my.example.com, Traffic Server would lookup the SRV record for _https._tcp.my.example.com, and use the records that reference 443 as the port (like _https._tcp.my.example.com. 10 IN SRV	10 1 443 server1.example.com). Note that the port returned in the SRV record MUST match the port being used for the origin (e.g. if the origin scheme is http and a default port, there should be a SRV record containing port 80).

[mlibbey]

Seems like we should probably write a paragraph some other place in the admin guide about this. Do you have suggestions where? (eg, do you remember part of the research path to look for the feature?)