Dynamic SCRIPT_NAME and compressed assets

[bcail]

This is using Django 4.2.3, django-compressor 4.4, and gunicorn 20.1.0. I'm trying out the dynamic SCRIPT_NAME feature (PR #876), but I'm having trouble getting it working.

I have a gunicorn app running on localhost:8000, and it's proxied through nginx at /app. Here's the nginx config:

location /app {
       proxy_pass              http://localhost:8000;
       proxy_set_header SCRIPT_NAME /app;
}

I ran the compress command.

When I hit a view on my app, I can see that SCRIPT_NAME is correctly coming through as /app, but the URL to the compressed static file is still just /static/..., without the /app prefix. Shouldn't the URL to the compressed static file be updated with the SCRIPT_NAME prefix?

From my settings file:

STATIC_URL = 'static/'
COMPRESS_ENABLED = True
COMPRESS_OFFLINE = True
COMPRESS_OUTPUT_DIR = ''

[bcail]

From PR #876, it looks like I'm supposed to add my own class that dynamically adds the SCRIPT_NAME prefix to the STATIC_URL (and COMPRESS_URL) (or am I supposed to use the LazyScriptNamePrefixedUrl class from the test code)? Should this feature be documented?

[carltongibson]

This looks like you're hitting this issue in Django...

https://code.djangoproject.com/ticket/34028

The long and short is that script name doesn't really work outside of the request-response cycle, so not with compress.

You might need to adjust your static url when running the command (or else find a way of making it work)

[bcail]

Thanks, @carltongibson. I actually don't have any static url in the compressed asset itself - this is just an issue with linking to the compressed asset when the response is generated.

I tried adding the LazyScriptNamePrefixedUrl class to my settings.py, and used that for COMPRESS_URL, and now it looks like the URL to the compressed asset does correctly contain the SCRIPT_NAME value.

So it looks like the feature does work, if the user adds a str subclass and uses that in their settings. Should this be added to the documentation?

[carltongibson]

...this is just an issue with linking to the compressed asset when the response is generated.

Following the discussion on the linked Django issue, in this circumstance SRIPT_NAME should be working no? 🤔

Maybe it's an issue with Django, maybe it's a configuration issue, but a minimal reproduce on a fresh project, and a report to Django is likely the way to go.

I don't think it's a compressor issue per se? 🤔 (Using the utility from compressor's test suite looks like patching over any issue, rather than addressing it 😬)

[carltongibson]

Reviewing the docs for FORCE_SCRIPT_NAME, SCRIPT_NAME is part of the WSGI environment, rather than an HTTP header, so I think you'd need to set it in your wsgi.py, or gunicorn config, rather than setting it as an HTTP header in Nginx.

https://docs.djangoproject.com/en/4.2/ref/settings/#force-script-name

Update: Although the gunicorn FAQ seems to imply either would be good: https://docs.gunicorn.org/en/stable/faq.html — you'll need to experiment to pin down exactly the behaviour.

[bcail]

@carltongibson thanks again for your comments.

Here's a question: if I want to mount my app at different prefixes (eg. /foo and /bar) at the same time (with offline compression and compressed assets served from /foo/static and /bar/static), does compressor support that? If so, how should I configure it (especially the COMPRESS_URL)?

What I'm seeing locally is that if I set COMPRESS_URL to a regular value like /static, the SCRIPT_NAME doesn't get added to the links on the page to the compressed assets. If I make the COMPRESS_URL a dynamic value where I add the SCRIPT_NAME on each call (ie. using the class from the compressor tests), then it works. (This seems to fit with what I see in the PR #876 where the feature was added.)

[carltongibson]

Grr. I'd have to play. (And there's not enough info, or a quick reproduce here, so that I can do that.) I'd reckon per-deploy settings with slight tweaks would do it. (I saw you commented about the offline context on another issue...)

[bcail]

Here's a playground project: https://github.com/bcail/dj_playground. I'm running it with: DJANGO_SETTINGS_MODULE=playground.settings gunicorn playground.wsgi:application

Here's my nginx config:

        location /foo/static {
                alias /var/www/playground_static;
        }

        location /bar/static {
                alias /var/www/playground_static;
        }

        location /foo {
                proxy_pass              http://localhost:8000;
                proxy_set_header SCRIPT_NAME /foo;
        }

        location /bar {
                proxy_pass              http://localhost:8000;
                proxy_set_header SCRIPT_NAME /bar;
        }

playground/settings.py has two options for COMPRESS_URL, one commented out. If I use the normal /static value, the compressed asset doesn't work. If I change it to the LazyScriptNamePrefixedUrl value, then the compressed asset works on both /foo/polls and /bar/polls.