duplicate ports across servers in nginx.conf

[Francis Daly]

On Wed, May 31, 2023 at 06:14:41AM +0000, Yuval Abadi via nginx wrote:

Hi there,

I don't speak for the project, but my guess is:

> If the configuration has 2 servers sharing the same name and the same port
> I got this warning:
> "nginx: [warn] conflicting server name "http://www.mut.com/" on 0.0.0.0:80, ignored"
> 
> Why not block this mistake?

If you have 20 server{}s, and 2 share the name and port, should the
entire system fail to start (or reload config)?

It seems friendlier to me to use the config as-provided, and alert on
things that are not used as the administrator apparently expected.

Some configuration issues are considered more important than some
others. This particular one is currently not considered "fatal".

> I assume the second server ignored, but why let it possible?

nginx does not control what the administrator types.

> If the servers do not have name
> I got this warning:
> nginx: [warn] conflicting server name "" on 0.0.0.0:9002, ignored
> nginx: [warn] conflicting server name "" on 0.0.0.0:80, ignored

Yes; it's the same message, showing the listen ip:port and server_name
values that are unexpected.

>  both warning:
> first no way for NGINX gives good warning, both server looks the same.

I agree that it would be even friendlier if the error message indicated
the filename and line number that the unexpected configuration came from;
I suspect that a patch to change that would be thoughtfully considered.

Maybe someone will be interested in providing that patch, now that the
issue has been mentioned.

(Maybe the only reason the log omits the filename is that no-one thought
to add it here, where it is added in other places. Or maybe it is harder
than that to implement.)

> if user did such mistake, better to block.

I disagree.

It appears that the current code disagrees too; maybe that will change
in the future.

> Why not enforce using at list one server have "listen   default_server  port"?

I think that is enforced already -- if you have more than one
"default_server", you get an "emerg" failure. If you have none explicitly,
then the implicit config applies -- and I would rather not lose the
implicit config.

> Why not enforce server names , and not let more than one server with same name?

I think that is what it is doing already; it considers it a "warning"
rather than an "emergency" configuration issue.

> Is NGINX  set the bit default_server ,on the first  "ngx_http_conf_addr_t", of the first server,  that read from conf file?  (if no default_server was defined)?
>

I'm not quite sure what you are asking: if it is about the code, it
is not hidden and is quite readable; if it is about which server is
default_server if none is explicit, then the documentation also describes
that -- the "implicit" default_server for a specific ip:port is the first
server{} that was read with that (possibly implicit) "listen" config.

Cheers,

	f
-- 
Francis Daly        francis at daoine.org