Fetching HTTP value into config at start-up

Server NGINX
1

Hi all,

I want to read some remote values via HTTP into nginx config variables,
just
once at nginx startup / reload time, and pass them as fastcgi_params
into
PHP scripts. I control the remote system, so I’ll know if it needs to
re-read and can send a HUP to nginx. I don’t need it to happen every
request
though, because the value won’t change for long periods - but it will
change
sometimes, and I don’t want to have push more config out to multiple
nginx
servers if I can avoid it.

Is there a way to do this that doesn’t create problems?

Here’s what I’ve tried so far.

This first one doesn’t work, because the “API [is] disabled in the
context
of set_by_lua*”:

set_by_lua $config_variable "
    local result = ngx.location.capture('http://url.to.fetch/')
    return result
"

(Same with ngx.socket.*)

This next one works; it feels horrible to do this but if it was just
once at
start-up, it might be OK - but this executes for every incoming request
(confirmed by using /bin/date as the ‘command’ and just hitting
refresh):

set_by_lua $config_variable "
    local command = "/usr/bin/curl http://url.to.fetch/"
    local handle = io.popen(command)
    local result = handle:read("*a")
    handle:close()
    return result
"

Same for this one, it executes for every request:

perl_set $config_variable '
    sub {
        $var = `/bin/date`;
        return $var;
    }
'

Is there a good way to do this, that only executes once, and doesn’t
have
horrible shell interactions?

Thanks very much for your help,
Igor

Posted at Nginx Forum:

2

Hello, igorclark

Perhahs you can create a shell to launch nginx, and before that, ejecute
a
shell to assign a environment variable as a result of the execution of a
program, or create (update) a file that is to be included from nginx
config
file when starting

Some ideas:

http://nginx.2469901.n2.nabble.com/Want-to-access-UNIX-environment-variable-td7584005.html
https://www.google.com/search?client=ubuntu&channel=fs&q=get+environment+variable+from+nginx&ie=utf-8&oe=utf-8

Greetings,

Oscar

3

Thanks Oscar. Yes I’d read that first page and a bunch of those search
results before. I guess I’ll end up writing custom config files per
environment, too, and maybe a script to regenerate and send a HUP to
nginx
when the data changes. I really wanted to avoid this because it’s just
one
more moving part that I’d rather not have.

It seems pretty reasonable to want to do this sort of thing just once at
startup. Even getting an env variable for every HTTP request seems kind
of
an overhead, however tiny. Maybe I’ll look at writing a module to do it
some
day. When I have enough time to learn how to write network-accessing
ngx_*
modules without breaking everything :wink:

Anyway, if anyone knows of another way to do it, that’d be great, but in
the
meantime I appreciate your response. Thanks.

Best,
Igor

Posted at Nginx Forum: