Directive inheritance

[Francis Daly]

On Fri, Oct 06, 2017 at 07:32:51PM +0000, Lucas Rolff wrote:

Hi there,

> I know that there’s some settings such as proxy_pass which can’t inherit from the parent location or server block, however – is there any semi-easy way to figure out if a directive in nginx or it’s modules gets inherited or not? (I don’t mind digging around in some nginx source code)

> I wonder if someone either knows a good way to figure out, or any document on the web that goes extensively into explaining what (might) inherit based on general design patterns.

My quick response, without doing too much research, is:

* "rewrite" module directives (if, return) don't inherit
* "handler" directives (proxy_pass, fastcgi_pass) don't inherit
* pretty much anything else that is valid in "location" does inherit

(That's probably not correct, but could be a good starting point for
experimentation.)

And be aware that inheritance is by replacement, or not at all -- so one
"add_header" in a location means that the only "add_header" relevant
to that location is the one that is there; while no "add_header" in a
location means that all of the ones inherited from server{} are relevant.


If you want the full details, it's a matter of Read The Fine Source --
each module has a "_module_ctx" which includes a function typically named
"_merge_loc_conf" which shows how each directive is set if it is not
defined in this location: unset, set to a default value, or inherited
from the previous level.

	f
-- 
Francis Daly        francis at daoine.org