location blocks, and if conditions in server context

[Lucas Rolff]

Hi peter,

I generate configs already using a template engine (more specific Laravel Blade), so creating the functionality in the template is easy, however, I generally don’t like having server blocks that can be 100s of lines because of repeating things

I don’t know the internals of nginx fully, how it uses memory when storing configs, but I would assume that inheritance is better than duplication in terms of memory usage.

I’m just wondering if there’s a way I can avoid the if condition within the location blocks.

- lucas

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________________________________
From: nginx <nginx-bounces at nginx.org> on behalf of Peter Booth <peter_booth at me.com>
Sent: Wednesday, March 7, 2018 11:08:40 PM
To: nginx at nginx.org
Subject: Re: location blocks, and if conditions in server context

I agree that avoiding if is a good thing. But avoiding duplication isn’t always good.

Have you considered a model where your configuration file is generated with a templating engine? The input file that you modify to add/remove/change configurations could be free of duplication but the conf file that nginx reads could be concrete and verbose

Sent from my iPhone

On Mar 7, 2018, at 11:55, Lucas Rolff <lucas at lucasrolff.com<mailto:lucas at lucasrolff.com>> wrote:

Hi guys,

I have a few hundred nginx zones, where I try to remove as much duplicate code as possible, and inherit as much as possible to prevent nginx from consuming memory (and also to keep things clean).

However I came across something today, that I don’t know how to get my head around without duplicating code, even within a single server context.

I have a set of distributed nginx servers, all these requires SSL certificates, where I use Let’s Encrypt to do this.
When doing the Let’s Encrypt validation, it uses a path such as /.well-known/acme-challenge/<hash>

For this, I made a location block such as:

    location ~* /.well-known {
        proxy_pass http://letsencrypt.validation.backend.com$request_uri;
    }

Basically, I proxy_pass to the backend where I actually run the acme client – works great.

However, I have an option to force a redirect from http to https, and I’ve implemented that by doing an if condition on the server block level (so not within a location):

    if ($sslproxy_protocol = "http") {
        return 301 https://$host$request_uri;
    }

This means I have something like:

1: location ~* /.well-known
2: if condition doing redirect if protocol is http
3: location /
4: location /api
5: location /test

All my templates include 1 to 3, and *might* have additional locations.
I’ve decided to not put e.g. location /api inside the location / - because there’s things I don’t want to inherit, thus keeping them at the same “level”, and not a location context inside a location context.
Things I don’t want to inherit, is stuff such as headers, max_ranges directive etc.

My issue is – because of this if condition that does the redirect to https – it also applies to my location ~* /.well-known – thus causing a redirect, and I want to prevent this, since it breaks the Let’s Encrypt validation (they do not accept 301 redirects).

A solution would be to move the if condition into each location block that I want to have redirected, but then I start repeating myself 1, 2 or even 10 times – which I don’t wanna do.

Is there a smart way without adding too much complexity, which is still super-fast (I know if is evil) ?

A config example is seen below:

server {
    listen              80;
    listen              443 ssl http2;

    server_name         secure.domain.com<http://secure.domain.com>;

    access_log /var/log/nginx/secure.domain.com<http://secure.domain.com> main;

    location ~* /.well-known {
        proxy_pass http://letsencrypt.validation.backend.com$request_uri;
    }

    if ($sslproxy_protocol = "http") {
        return 301 https://$host$request_uri;
    }

    location / {

        expires 10m;
        etag off;

        proxy_ignore_client_abort   on;
        proxy_intercept_errors      on;
        proxy_next_upstream         error timeout invalid_header;
        proxy_ignore_headers        Set-Cookie Vary X-Accel-Expires Expires Cache-Control;
        more_clear_headers          Set-Cookie Cookie Upgrade;

        proxy_cache                 one;
        proxy_cache_min_uses        1;
        proxy_cache_lock            off;
        proxy_cache_use_stale       error timeout invalid_header updating http_500 http_502 http_503 http_504;

        proxy_cache_valid 200           10m;
        proxy_cache_valid any           1m;

        proxy_cache_revalidate      on;
        proxy_ssl_server_name       on;

        include /etc/nginx/server.conf;

        proxy_set_header Host backend-host.com<http://backend-host.com>;

        proxy_cache_key    "http://backend-host.com-1-$request_uri";
        proxy_pass         http://backend-host.com$request_uri;

        proxy_redirect              off;
    }
}

Thank you in advance!

Best Regards,
Lucas Rolff
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